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Qu, Dongfang, Peter Frykman, Lars Stemmerik, Klaus Mosegaard i Lars Nielsen. "Upscaling of outcrop information for improved reservoir modelling – exemplified by a case study on chalk". Petroleum Geoscience 27, nr 4 (14.04.2021): petgeo2020–126. http://dx.doi.org/10.1144/petgeo2020-126.
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Outcrops are valuable for analogous subsurface reservoirs in supplying knowledge of fine-scale spatial heterogeneity pattern and stratification types, which are difficult to obtain from subsurface reservoir cores, well logs or seismic data. For petrophysical properties in a domain where the variations are relatively continuous and not dominated by abrupt contrasts, the spatial heterogeneity pattern can be characterized by a semivariogram model. The outcrop information therefore has the potential to constrain the semivariogram for subsurface reservoir modelling, even though it represents different locations and depths, and the petrophysical properties may differ in magnitude or variance. However, the use of outcrop-derived spatial correlation information for petrophysical property modelling in practice has been challenged by the scale difference between the small support volume of the property measurements from outcrops and the typically much larger grid cells used in reservoir models. With an example of modelling the porosity of an outcrop chalk unit in eastern Denmark, this paper illustrates how the fine-scale spatial correlation information obtained from the sampling of outcrops can be transferred to coarser-scale models of analogue rocks. The workflow can be applied to subsurface reservoirs and ultimately improves the representation of geological patterns in reservoir models.
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Ramdani, Ahmad, Andika Perbawa, Ingrid Puspita i Volker Vahrenkamp. "Acoustic impedance to outcrop: Presenting near-surface seismic data as a virtual outcrop in carbonate analog studies". Leading Edge 41, nr 9 (wrzesień 2022): 599–610. http://dx.doi.org/10.1190/tle41090599.1.
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Outcrop analogs play a central role in understanding subseismic interwell depositional facies heterogeneity of carbonate reservoirs. Outcrop geologists rarely utilize near-surface seismic data due to the limited vertical resolution and difficulty visualizing seismic signals as “band-limited rocks.” This study proposes a methodology using a combination of forward modeling and conditional generative adversarial network (cGAN) to translate seismic-derived acoustic impedance (AI) into a pseudo-high-resolution virtual outcrop. We tested the methodology on the Hanifa reservoir analog outcropping in Wadi Birk, Saudi Arabia. We interpret a 4 km long outcrop photomosaic from a digital outcrop model (DOM) for its depositional facies, populate the DOM with AI properties, and forward calculate the band-limited AI of the DOM facies using colored inversion. We pair the synthetic band-limited AI with DOM facies and train them using a cGAN. Similarly, we pair the DOM facies with outcrop photos and train them using a cGAN. We chain the two trained networks and apply them to the approximately 600 m long seismic-derived AI data acquired just behind the outcrop. The result translates AI images into a virtual outcrop “behind-the-outcrop” model. This virtual outcrop model is a visual medium that operates at a resolution and format more familiar to outcrop geologists. This model resolves subseismic stratigraphic features such as the intricate downlap-onlap stratal termination at scales of tens of centimeters and the outline of buildup facies, which are otherwise unresolvable in the band-limited AI.
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Anne, M. Schwab, W. Homewood Peter, S. P. van Buchem Frans i Razin Philippe. "Seismic forward model of a Natih Formation outcrop: the Adam Foothills Transect (northern Oman)". GeoArabia 10, nr 1 (1.01.2005): 17–44. http://dx.doi.org/10.2113/geoarabia100117.
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ABSTRACT The platform carbonates of the Natih Formation (Albian-Turonian) are hydrocarbon reservoirs throughout the Middle East. This study uses a high-resolution sequence stratigraphic model built from the Natih outcrops of the Adam Foothills Transect, in northern Oman, as the basis for the construction of synthetic seismic sections along the Natih outcrops. The model covers the seaward progression from a proximal carbonate platform to a distal intrashelf basin. Three third-order depositional sequences had been identified and correlated across the outcrops, and facies were mini-core plugged for petrophysical data measurement, which were then used to construct an impedance model from the stratigraphic model. This impedance model was used to construct synthetic seismic sections with a zero phase Ricker wavelet at varying peak frequencies (80 Hz, 60 Hz and 40 Hz). The high-frequency synthetic seismic identified seismic characteristics of specific depositional environments, notably the organic-rich intrashelf basin, the platform margin and the platform interior. These seismic characteristics were very subtle on the lower frequency data, but could nonetheless be identified. A seismic line passing through a nearly analogous setting in the subsurface Natih was used to try and identify the characteristics observed on the synthetic seismic data. Many of the synthetically-produced characteristics were found on the industry seismic, which shows that this method is a good way of using the detail of the outcrop to help with predictions on the lower frequency/resolution seismic.
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Milad, Benmadi, i Roger Slatt. "Impact of lithofacies variations and structural changes on natural fracture distributions". Interpretation 6, nr 4 (1.11.2018): T873—T887. http://dx.doi.org/10.1190/int-2017-0138.1.
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Understanding and predicting the impact of lithofacies changes and structural effects on fracture distributions is vitally important to optimize a drilling location and orientation. To evaluate and model fracture intensity of the Late Ordovician-Silurian-Early Devonian Hunton Group carbonates in Oklahoma, natural fractures were studied at different scales using borehole images, three outcrops (two horizontally bedded outcrops and one anticline outcrop), and seismic data. Natural fractures identified from eight horizontal well borehole images include conductive (open), partially open, mineralized (closed), and induced fractures. Four fracture sets were identified from borehole images and from the two horizontally bedded outcrops. A 3D fracture intensity model was populated, from the fracture intensity logs at the boreholes, and compared with a 3D lithofacies model. Principal component analysis from lithology logs produced input to a self-organizing map to classify and cluster electrofacies. Thin sections and borehole images corroborate the electrofacies around the wellbores, whereas 3D seismic data were used as constraints to build a 3D lithofacies model. A 3D lithofacies model resulted from the extrapolation of the lithofacies from the well scale to the regional seismic scale. In this study area, lithofacies and structure are interrelated and control fracture distributions. Lithofacies is the primary control, whereas structure is the secondary control. Three lithofacies (wackestone, mudstone, and mud-dominated wackestone) were identified. A positive relationship between the fracture intensity and the presence of wackestone was observed at well locations and in the mapped subsurface area. The other two lithofacies do not exhibit high fracture abundance. Structural effects influence fracture distributions near faults and positive curvature areas in the subsurface measured on the 3D seismic data. For the Hunton Anticline outcrop exposure, there was a positive linear relationship between fracture intensity and changes in curvature for the mudstone and mud-dominated wackestone and an exponential relationship for the wackestone textures. The integration of lithology and structure from multidisciplinary, multiscalar data (i.e., outcrops, image logs, and 3D seismic) helps to identify and predict the fractured zones in the Hunton carbonates and can be used for horizontal well planning as well as stimulation programs. More importantly, this study proposes a generic model to predict the variability of fractures at different scales of curvatures combined with lithology changes and can be used for other carbonate reservoirs.
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Wang, Fred P., Jiachun Dai i Charles Kerans. "Modeling dolomitized carbonate‐ramp reservoirs: A case study of the Seminole San Andres unit—Part II, Seismic modeling, reservoir geostatistics, and reservoir simulation". GEOPHYSICS 63, nr 6 (listopad 1998): 1876–84. http://dx.doi.org/10.1190/1.1444480.
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In part I of this paper, we discussed the rock‐fabric/petrophysical classes for dolomitized carbonate‐ramp rocks, the effects of rock fabric and pore type on petrophysical properties, petrophysical models for analyzing wireline logs, the critical scales for defining geologic framework, and 3-D geologic modeling. Part II focuses on geophysical and engineering characterizations, including seismic modeling, reservoir geostatistics, stochastic modeling, and reservoir simulation. Synthetic seismograms of 30 to 200 Hz were generated to study the level of seismic resolution required to capture the high‐frequency geologic features in dolomitized carbonate‐ramp reservoirs. At frequencies <70 Hz, neither the high‐frequency cycles nor the rock‐fabric units can be identified in seismic data because the tuning thickness of seismic data is much greater than the average thickness of high‐frequency cycles of 6 m. At frequencies >100 Hz, major high‐porosity and dense mudstone units can be better differentiated, while the rock‐fabric units within high‐frequency cycles can be captured at frequencies higher than 200 Hz. Seismic inversion was performed on the 30- to 200-Hz synthetic seismograms to investigate the level of seismic resolution required to recover the high‐resolution inverted impedance logs. When seismic data were noise free, wavelets were known and sampling rates were high; deconvolution techniques yielded perfect inversion results. When the seismic data were noisy, the inverted reflectivity profiles were poor and complicated by numerous high‐frequency spikes, which can be significantly removed using the moving averaging techniques. When wavelets were not known, the predictive deconvolution gave satisfactory inversion results. These results suggest that interwell information required for reservoir characterization can be recovered from low‐frequency seismic data by inversion. Outcrop data were collected to investigate effects of sampling interval and scale‐up of block size on geostatistical parameters. Semivariogram analysis of outcrop data showed that the sill of log permeability decreases and the correlation length increases with an increase of horizontal block size. Permeability models were generated using conventional linear interpolation, stochastic realizations without stratigraphic constraints, and stochastic realizations with stratigraphic constraints. The stratigraphic feature of upward‐shoaling sequences can be modeled in stochastic realizations constrained by the high‐frequency cycles and rock‐fabric flow units. Simulations of a fine‐scale Lawyer Canyon outcrop model were used to study the factors affecting waterflooding performance. Simulation results show that waterflooding performance depends strongly on the geometry and stacking pattern of the rock‐fabric units and on the location of production and injection wells.
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Wang, Fred P., F. Jerry Lucia i Charles Kerans. "Modeling dolomitized carbonate‐ramp reservoirs: A case study of the Seminole San Andres unit—Part I, Petrophysical and geologic characterizations". GEOPHYSICS 63, nr 6 (listopad 1998): 1866–75. http://dx.doi.org/10.1190/1.1444479.
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Major issues in characterizing carbonate‐ramp reservoirs include geologic framework, seismic stratigraphy, interwell heterogeneity including rock fabric facies and permeability structure, and factors affecting petrophysical properties and reservoir simulation. The Seminole San Andres unit, Gaines County, West Texas, and the San Andres outcrop of Permian age in the Guadalupe Mountains, New Mexico, were selected for an integrated reservoir characterization to address these issues. The paper is divided into two parts. Part I covers petrophysical and geologic characterization, and part II describes seismic modeling, reservoir geostatistics, stochastic modeling, and reservoir simulation. In dolomitic carbonates, two major pore types are interparticle (includes intergranular and intercrystalline) and vuggy. For nonvuggy carbonates the three important petrophysical/rock fabric classes are (I) grainstone, (II) grain‐dominated packstone and medium crystalline dolostone, and (III) mud‐dominated packstone, wackestone, mudstone, and fine crystalline dolostone. Core data from Seminole showed that rock fabric and pore type have strong positive correlations with absolute and relative permeabilities, residual oil saturation, waterflood recovery, acoustic velocity, and Archie cementation exponent. Petrophysical models were developed to estimate total porosity, separate‐vug porosity, permeability, and Archie cementation exponent from wireline logs to account for effects of rock fabric and separate‐vug porosity. The detailed and regional stratigraphic models were established from outcrop analogs and applied to seismic interpretation and wireline logs and cores. The aggradational seismic character of the San Andres Formation at Seminole is consistent with the cycle stacking pattern within the reservoir. In particular, the frequent preservation of cycle‐based mudstone units in the Seminole San Andres unit is taken to indicate high accommodation associated with greater subsidence rates in this region. A model for the style of high‐frequency cyclicity and the distribution of rock‐fabric facies within cycles was developed using continuous outcrop exposures at Lawyer Canyon. This outcrop model was applied during detailed core descriptions. These, together with detailed analysis of wireline log signatures, allowed construction of the reservoir framework based on genetically and petrophysically significant high‐frequency cycles. Petrophysical properties of total and separate‐vug porosities, permeability, water saturation, and rock fabrics were calculated from wireline log data. High‐frequency cycles and rock‐fabric units are the two critical scales for modeling carbonate‐ramp reservoirs. Descriptions of rock‐fabric facies stacked within high‐frequency cycles provide the most accurate framework for constructing geologic and reservoir models. This is because petrophysical properties can be better grouped by rock fabrics than depositional facies. The permeability‐thickness ratios among these rock fabric units can then be used to approximate fluid flow and recovery efficiency.
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Fakhruddin, Rakhmat, Taufi k. Ramli i Hanif Mersil Saleh. "WELL AND OUTCROP CORRELATION IN THE EASTERN PART OF AKIMEUGAH BASIN, PAPUA: MESOZOIC PLAY POTENTIAL". Scientific Contributions Oil and Gas 41, nr 2 (29.06.2020): 75–87. http://dx.doi.org/10.29017/scog.41.2.336.
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Mesozoic sediments are the main objective for hydrocarbon exploration in the eastern part of Akimeugah Basin, Papua. However, little information is currently available on paleogeography and subsurface distribution of the Mesozoic rock unit. This study analyzed Mesozoic rock unit from outcrops at Wamena and surrounding area to wells data in the eastern part of Akimeugah Basin, Papua. Outcrop and well correlation was made to interpret paleogeography of Mesozoic unit. This study was using existin 2D seismic and passive seismic tomography data to determine the distribution of Mesozoic rock unit in the subsurface and its hydrocarbon potential. The Mesozoic rock unit in the eastern part of Akimeugah Basin is divided into four formations based on their lithological characteristic. Respectively from old to young, Kopai, Woniwogi, Piniya and Ekmai Formation. The depositional environment of Mesozoic rock unit in the southern part of the study area is shore/tidal to shelf and basin fl oor in the northern part. Three Mesozoic potential plays in the studied area are divided into 1) Central Range Mountains thrust-fold belt play, 2) Akimeugah low land thrust-fold belt play and 3) Tanah Merah pinch-out play. The results presented in this paper are expected to be a guide for further hydrocarbon exploration in the study area. Mesozoic sediments are the main objective for hydrocarbon exploration in the eastern part of Akimeugah Basin, Papua. However, little information is currently available on paleogeography and subsurface distribution of the Mesozoic rock unit. This study analyzed Mesozoic rock unit from outcropsat Wamena and surrounding area to wells data in the eastern part of Akimeugah Basin, Papua. Outcrop and well correlation was made to interpret paleogeography of Mesozoic unit. This study was using existing 2D seismic and passive seismic tomography data to determine the distribution of Mesozoic rock unit in the subsurface and its hydrocarbon potential. The Mesozoic rock unit in the eastern part of Akimeugah Basin is divided into four formations based on their lithological characteristic. Respectively from old to young, Kopai, Woniwogi, Piniya and Ekmai Formation. The depositional environment of Mesozoic rock unit in the southern part of the study area is shore/tidal to shelf and basin fl oor in the northern part. Three Mesozoic potential plays in the studied area are divided into 1) Central Range Mountains thrust-fold belt
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Gai, Shaohua, Ailin Jia, Yunsheng Wei i Ruohan Liu. "Characterization and Modelling of Multiscale Natural Fractures in Shale Reservoirs: A Case Study from a Block in the Southern Sichuan Basin". Geofluids 2022 (7.10.2022): 1–11. http://dx.doi.org/10.1155/2022/6872983.
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Natural fractures are vital to the efficiencies of drilling and completion operation. The purpose of this paper is to characterize and model multiscale natural fractures in shale reservoirs. Based on the seismic and log responses, as well as outcrop and core observations, we divide natural fractures into Macro, Meso, and Micro three scales. Macroscale fractures are the faults picked directly in seismic profiles. Also, Mesoscale fractures are the natural fracture corridors analyzed by ant tracking technique in 3D seismic data. Furthermore, Microscale fractures are the fractures observed in imaging logs and cores. The fracture intensity is obtained by the correlation between ant tracking attributes and fracture density in borehole. The fracture aperture, dip, and azimuth are three main parameters, which are recognized by the loggings and cores. Stochastic modelling is applied to factures. We find that faults identified by the ant tracking result are excellent in line with Macroscale faults interpreted directly from seismic data. In addition, Mesoscale fractures are indicated from the ant tracking result, which are in accord with breakpoint in the well and in keeping with tectonic history of the area. Such high consistency indicates the ant tracking result is reliable. Moreover, image logs and cores reveal that it mainly develops high angle natural fractures and the fracture aperture is about 1 mm. The fracture strike includes three sets (NNW-SSE, NE-SW, and NNE-SSW). The distribution of the natural fractures in discrete fracture network (DFN) system is distributed controlled by the ant tracking result. Comparing the histograms of DFN results and fracture characterized by seismic and logging responses, as well as outcrop and core observation, it suggests that the major part of the observed natural fractures is retained into our DFN model.
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Stucchi, Eusebio, Francesco Mirabella i Maria Grazia Ciaccio. "Comparison between reprocessed seismic profiles: Seismologic and geologic data — A case study of the Colfiorito earthquake area". GEOPHYSICS 71, nr 2 (marzec 2006): B29—B40. http://dx.doi.org/10.1190/1.2187709.
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Seismic reflection data are used to reconstruct the subsurface geologic structures below the Umbria-Marche region in Italy, a highly seismogenic area with a recent history of seismic activity (the 1997–1998 Colfiorito sequence). We reprocess three vibroseis seismic profiles (acquired in the early 1980s for hydrocarbon exploration) whose stacked sections were optimized for relatively deep oil targets. On the reprocessed seismic profile closest to the epicentral area, we construct the main reflectors to a depth of about 4 s (two-way time) and compare this interpretation with the available hypocenters of the 1997 earthquakes. The improvements in visualizing the shallow and deep reflections provide a better correlation between the reflectors and the observed surface structures as well as a better delineation of the basement-rock geometry. We find that part of the Colfiorito sequence is localized around some of the reflectors in the reflection profile, which we interpret as related to the active normal faults that outcrop at the surface.
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Kokusho, Takaji, i Tomohiro Ishizawa. "Site Amplification during Strong Earthquakes Investigated by Vertical Array Records". Geosciences 11, nr 12 (14.12.2021): 510. http://dx.doi.org/10.3390/geosciences11120510.
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A number of vertical array records during eight destructive earthquakes in Japan are utilized, after discussing criteria for desirable requirements of vertical arrays, to formulate seismic amplification between ground surface and outcrop base for seismic zonation. A correlation between peak spectrum amplification and Vs (S-wave velocity) ratio (base Vs/surface Vs) was found to clearly improve by using Vs in an equivalent surface layer wherein predominant frequency or first peak is exerted, though the currently used average Vs in top 30 m is also meaningful, correlating positively with the amplification. We also found that soil nonlinearity during strong earthquakes has only a marginal effect even in soft soil sites on the amplification between surface and outcrop base except for ultimate soil liquefaction failure, while strong nonlinearity clearly appears in the vertical array amplification between surface and downhole base. Its theoretical basis has been explained by a simple study on a two-layered system in terms of radiation damping and strain-dependent equivalent nonlinearity.
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Mullins, James, Helena van Der Vegt i John Howell. "Combining process-based models and multiple-point geostatistics for improved reservoir modelling". Petroleum Geoscience 27, nr 3 (26.02.2021): petgeo2020–012. http://dx.doi.org/10.1144/petgeo2020-012.
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The construction of subsurface reservoir models is typically aided by the use of outcrops and modern analogue systems. We show how process-based models of depositional systems help to develop and substantiate reservoir architectural concepts. Process-based models can simulate assumptions relating to the physical processes influencing sedimentary deposition, accumulation and erosion on the resultant 3D sediment distribution. In this manner, a complete suite of analogue geometries can be produced by implementing different sets of boundary conditions based on hypotheses of depositional controls. Simulations are therefore not driven by a desired/defined outcome in the depositional patterns, but their application to date in reservoir modelling workflows has been limited because they cannot be conditioned to data such as well logs or seismic information.In this study a reservoir modelling methodology is presented that addresses this problem using a two-step approach: process-based models producing 3D sediment distributions that are subsequently used to generate training images for multi-point geostatistics.The approach has been tested on a dataset derived from a well-exposed outcrop from central Utah. The Ferron Sandstone Member includes a shallow-marine deltaic interval that has been digitally mapped using a high-resolution unmanned aerial vehicle (UAV) survey in 3D to produce a virtual outcrop (VO). The VO was used as the basis to build a semi-deterministic outcrop reference model (ORM) against which to compare the results of the combined process/multiple-point statistics (MPS) geostatistical realizations. Models were compared statically and dynamically through flow simulation.When used with a dense well dataset, the MPS realizations struggle to account for the high levels of non-stationarity inherent in the depositional system that are captured in the process-based training image. When trends are extracted from the outcrop analogue and used to condition the simulation, the geologically realistic geometries and spatial relationships from the process-based models are directly imparted onto the modelling domain, whilst simultaneously allowing the facies models to be conditioned to subsurface data.When sense-checked against preserved analogues, this approach reproduces more realistic architectures than traditional, more stochastic techniques.
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Van Houtte, C., O. J. Ktenidou, T. Larkin i A. Kaiser. "Reference stations for Christchurch". Bulletin of the New Zealand Society for Earthquake Engineering 45, nr 4 (31.12.2012): 184–95. http://dx.doi.org/10.5459/bnzsee.45.4.184-195.
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During the Canterbury earthquake sequence, the observed level of ground motion on the soft soils of Christchurch was very strong and highly variable. Many studies are now emerging that analyse the amplification effect of these soft soils, usually by estimating a frequency-dependent amplification function relative to a rock outcrop station, or ‘reference site’. If the rock outcrop has its own amplification due to weathering or topographic effects, then the calculated amplification for the soil sites can be compromised. This study examines ten seismic stations in Canterbury to determine the best reference site for Christchurch, using the horizontal-to-vertical spectral ratio (HVSR) method for S-wave shaking. More broadly, this study uses HVSR to expand existing knowledge of the dynamic characteristics of seismic stations in the Canterbury area. Most rock stations show their own local amplification effects that reduce their individual ability to be used as reference stations. The recently installed Huntsbury station (HUNS) appears to be the best reference site for Christchurch, but this will need to be verified when more records become available. In the meantime, the D13C temporary station is currently the best reference station for site effect studies in both Christchurch and Lyttelton.
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Davis, E. E., D. S. Chapman, M. J. Mottl, W. J. Bentkowski, K. Dadey, C. Forster, R. Harris i in. "FlankFlux: an experiment to study the nature of hydrothermal circulation in young oceanic crust". Canadian Journal of Earth Sciences 29, nr 5 (1.05.1992): 925–52. http://dx.doi.org/10.1139/e92-078.
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The sediment-buried eastern flank of the Juan de Fuca Ridge provides a unique environment for studying the thermal nature and geochemical consequences of hydrothermal circulation in young ocean crust. Just 18 km east of the spreading axis, where the sea-floor age is 0.62 Ma, sediments lap onto the ridge flank and create a sharp boundary between sediment-free and sediment-covered igneous crust. Farther east, beneath the nearly continuous turbidite sediment cover of Cascadia Basin, the buried basement topography is extremely smooth in some areas and rough in others. At a few isolated locations, small volcanic edifices penetrate the sediment surface. An initial cruise in 1978 and two subsequent cruises in 1988 and 1990 on this sedimented ridge flank have produced extensive single-channel seismic coverage, detailed heat flow surveys co-located with seismic lines, and pore-fluid geochemical profiles of piston and gravity cores taken over heat flow anomalies. Complementary multichannel seismic reflection data were collected across the ridge crest and eastern flank in 1985 and 1989. Preliminary results of these studies provide important new information about hydrothermal circulation in ridge flank environments. Near areas of extensive basement outcrop, ventilated hydrothermal circulation in the upper igneous crust maintains temperatures of less than 10–20 °C; geochemically, basement fluids are virtually identical to seawater. Turbidite sediment forms an effective hydrologic and geochemical seal that restricts greatly any local exchange of fluid between the igneous crust and the ocean. Once sediment thickness reaches a few tens of metres, local vertical fluid flux through the sea floor is limited to rates of less than a few millimetres per year. Fluids and heat are transported over great distances laterally in the igneous crust beneath sediment however. Heat flow, basement temperatures, and basement fluid compositions are unaffected by ventilated circulation only where continuous sediment cover extends more than 15–20 km away from areas of extensive outcrop. Where small basement edifices penetrate the sediment cover in areas that are otherwise fully sealed, fluids discharge at rates sufficient to cause large heat flow and pore-fluid geochemical anomalies in the immediate vicinity of the outcrops. After complete sediment burial, hydrothermal circulation continues in basement. Estimated basement temperatures and, to the limited degree observed, fluid compositions are uniform over large areas despite large local variations in sediment thickness. Because of the resulting strong relationship between heat flow and sediment thickness, it is not possible, in most areas, to detect any systematic pattern of heat flow that might be associated with cellular hydrothermal circulation in basement. However, an exception to this occurs at one location where the sediment thickness is sufficiently uniform to allow detection of a systematic variation in heat flow that can probably be ascribed to cellular circulation. At that location, temperatures at the sediment–basement interface vary smoothly between about 40 and 50 °C, with a half-wavelength of about 700 m. A permeable-layer thickness of similar dimension is inferred by assuming that circulation is cellular with an aspect ratio of roughly one. This thickness is commensurate with the subbasement depth to a strong seismic reflector observed commonly in the region. Seismic velocities in the igneous crustal layer above this reflector have been observed to be low near the ridge crest and to increase significantly where the transition from ventilated to sealed hydrothermal conditions occurs, although no associated reduction in permeability can be ascertained from the thermal data.
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BEZERRA, FRANCISCO HILÁRIO REGO, VANILDO PEREIRA DA FONSCECA i FRANCISCO PINHEIRO LIMA FILHO. "Seismites: origin, criteria of identification and examples from the Quaternary record of Northeastern Brasil". Pesquisas em Geociências 28, nr 2 (31.12.2001): 205. http://dx.doi.org/10.22456/1807-9806.20295.
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Seismites are soft-sediment features produced by (paleo)earthquakes. They are formed after sediment deposition, before sediment compaction, and during sudden breakdown of a loosely packet, water saturated grain framework. Fundamental controls on seismite generation are exerted mainly by earthquake size, sediment properties, and water-table depth. Hydroplastic deformation, liquefaction, and fluidization are the three mechanisms related to seismite origin. The most common types of seismites are hydroplastic mixing layers, pillars, pockets, dikes, sills, and folds. Outcrop features are among the most valuable tools for deciphering seismic events in the past. Seismites have been described in many intraplate settings. In northeastern Brazil, earthquake swarms, including events up to 5.2 Mb, induced soft-sediment deformation in at least two historical cases. In this region, seismites occur in the Quaternary record of the Jaguaribe, Açu, and Potengi valleys, where a great variety of types are observed. They are particularly abundant in gravelly and sandy alluvial sediments. But they also occur in deltaic and lagoonal deposits. The study of seismites is particularly useful in areas lacking structural data. Seismite investigation is also important to extent the earthquake record far beyond the instrumental period of seismic observation.
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Kammann, Janina, Alireza Malehmir, Bojan Brodic, Mattia Tagliavento, Lars Stemmerik, Egon Nørmark, Holger Lykke-Andersen i Lars Nielsen. "Deep onshore reflection seismic imaging of the chalk group strata using a 45 kg accelerated weight-drop and combined recording systems with dense receiver spacing". GEOPHYSICS 84, nr 4 (1.07.2019): B259—B268. http://dx.doi.org/10.1190/geo2018-0755.1.
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The Chalk Group forms important hydrocarbon reservoirs offshore and water aquifers onshore Denmark. Within a day of fieldwork, a 450 m long reflection seismic profile was acquired onshore in an area in southeast Denmark, where the Chalk Group extends almost to the surface and is approximately 900 m thick. The main objective of the study was to image the complete Chalk Group in high resolution and to study the origin of reflectivity within the different chalk units. A 45 kg accelerated weight-drop source, in combination with dense receiver spacing using microelectromechanical sensors mounted on a streamer and 48 planted geophones, was used for data acquisition. The profile runs subparallel to the cliffs of Stevns, and the recorded signal reaches the base of the Chalk Group at approximately 600 ms. The fully cored 443 m-deep Stevns-1 borehole, which is located at the recorded seismic line, provides excellent control on lithologic and facies changes. Comparison with the borehole data demonstrates that our seismic data set provides a high-resolution image of the internal layering of the Chalk Group. We find that the internal reflection coefficients of the Chalk Group are, in general, small based on wireline-log data. However, the reflected amplitudes are just big enough to be recorded with the receiver setup used, even from the pure chalk beds of the Chalk Group. The reflectivity seen on the high-resolution seismic profile is influenced by occurrences of clay-enriched chalk layers. Flint bands consisting of numerous flint nodules are a characteristic of the uppermost part of the Chalk Group at Stevns. The flint nodules appear to produce significant scattering of the seismic signals, and flint-rich layers appear with diffuse internal reflectivity characteristics. Outcrop-scale mound structures in Danian and Upper Cretaceous outcrops are for the first time seismically resolved.
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Ramdani, Ahmad, Thomas Finkbeiner, Viswasanthi Chandra, Pankaj Khanna, Sherif Hanafy i Volker Vahrenkamp. "Multiattribute probabilistic neural network for near-surface field engineering application". Leading Edge 40, nr 11 (listopad 2021): 794–804. http://dx.doi.org/10.1190/tle40110794.1.
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Unconfined compressive strength (UCS) is an important rock parameter required in the engineering design of structures built on top or within the interior of rock formations. In a site investigation project, UCS is typically obtained discretely (through point-to-point measurement) and interpolated. This method is less than optimal to resolve meter-scale UCS variations of heterogenous rock such as carbonate formations in which property changes occur within data spacing. We investigate the geotechnical application of multiattribute analysis based on near-surface reflection seismic data to probe rock formations for their strength attributes at meter-scale variability. Two Late Jurassic outcrops located in central Saudi Arabia serve as testing sites: the Hanifa Formation in Wadi Birk and the Jubaila Formation in Wadi Laban. The study uses core and 2D seismic profiles acquired in both sites, from which we constrain UCS, acoustic velocity, density, and gamma-ray values. A positive linear correlation between UCS and acoustic impedance along the core indicates that seismic attributes can be utilized as a method to laterally extrapolate the UCS away from the core location. Seismic colored inversion serves as input for neural network multiattribute analysis and is validated with a blind test. Results from data at both outcrop sites indicate a high degree of consistency with an absolute UCS error of approximately 5%. We also demonstrate the applicability of predicted UCS profiles to interpret mechanical stratigraphy and map lateral UCS heterogeneities. These findings provide a less expensive alternative to constrain UCS from limited core data on a field-scale site engineering project.
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Kelly, Trevor B., i Grant D. Wach. "Analysis of factors influencing the interpretation of a digitally examined fluvial meanderbelt system: Joggins Formation, Nova Scotia". Canadian Journal of Earth Sciences 57, nr 4 (kwiecień 2020): 524–41. http://dx.doi.org/10.1139/cjes-2018-0263.
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Clastic reservoir exploration, development, and exploitation are inherently complex with recovery depending largely on the understanding of sand body architecture and interlayered clayey/silty baffles and barriers. Numerous data collection techniques and methods are now widely available for helping to enrich reservoir outcrop analogue data extraction from the well scale to the larger seismic scale. This integrated study uses the inherited, combined data from a localized light detection and ranging survey, measurements taken from a portable handheld spectrometer and air permeameter, in addition to total (or absolute) porosity measurements from thin sections to assist with the analysis of components influencing the interpretation of a digitally analyzed fluvial meanderbelt system outcrop. The purpose is not to perform a detailed reservoir characterization or to model a potential reservoir, but rather to study a section of a reservoir analogue and apply reservoir geology with integrated data collection techniques to highlight potential benefits and shortcomings of this type of approach. A point cloud survey generated from light detection and ranging, coupled with other tools including a portable handheld spectrometer and permeameter, supplements data from the light detection and ranging scan and increases the confidence of interpretations. Spectrometer measurements recorded at the outcrop are used to generate a pseudo-gamma log. Handheld air permeameter measurements give a sense of the permeability of corresponding lithologies, as well as the variability in permeability of the reservoir both laterally and vertically. Light detection and ranging also provides important information regarding rock properties. The high detail of the outcrop images is used for the assessment of reservoir characteristics. The reservoir data leads to an increased understanding of subsurface reservoirs, particularly of the fluvial meanderbelt type. This study shows the importance and drawbacks of a combined digital data collection approach for the analysis of a sedimentary outcrop.
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Dubos-Sallée, Noalwenn, André Fourno, Jeanneth Zarate-Rada, Véronique Gervais, Patrick N. J. Rasolofosaon i Olivier Lerat. "A complete workflow applied on an oil reservoir analogue to evaluate the ability of 4D seismics to anticipate the success of a chemical enhanced oil recovery process". Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 75 (2020): 18. http://dx.doi.org/10.2516/ogst/2020011.
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In an Enhanced Oil Recovery (EOR) process, one of the main difficulties is to quickly evaluate if the injected chemical products actually improve oil recovery in the reservoir. The efficiency of the process can be monitored in the vicinity of wells, but it may take time to estimate it globally in the reservoir. The objective of this paper is to investigate the ability of 4D seismics to bridge this gap and to help predict the success or breakdown of a production strategy at reservoir scale. To that purpose, we consider a complete workflow for simulating realistic reservoir exploitation using chemical EOR and 4D seismic modeling. This workflow spans from geological description to seismic monitoring simulation and seismic attributes analysis, through geological and reservoir modeling. It is applied here on a realistic case study derived from an outcrop analog of turbiditic reservoirs, for which the efficiency of chemical EOR by polymer and surfactant injection is demonstrated. For this specific field monitoring application, the impact of both waterflooding and proposed EOR injection is visible on the computed seismics. However, EOR injection induces a more continuous water front that can be clearly visible on seismics. In this case, the EOR efficiency can thus be related to the continuity of the water front as seen on seismics. Nevertheless, in other cases, chemical EOR injections may have more moderate impacts, or the field properties may be less adapted to seismic monitoring. This points out the importance of the proposed workflow to check the relevance of seismic monitoring and to design the most adapted monitoring strategy. Numerous perspectives are proposed at the end of the paper. In particular, experts of the different disciplines involved in the proposed workflow can benefit from the availability of a complete set of well-controlled data of various types to test and improve their own tools. In contrast, the non-experts can easily and quickly benefit from “hands-on” experiments for understanding the involved phenomena. Furthermore, the proposed workflow can be directly applied to geological reservoirs all over the world.
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Carpenter, Chris. "Data-Analysis Approach Aids Reservoir-Quality Prediction of Microporous Carbonates". Journal of Petroleum Technology 74, nr 02 (1.02.2022): 89–92. http://dx.doi.org/10.2118/0222-0089-jpt.
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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 19972, “Improving Reservoir-Quality Prediction of Microporous Carbonates Using a Multiscale Geophysical Data-Analysis Approach,” by Ahmad Ramdani, SPE, Viswasanthi Chandra, and Thomas Finkbeiner, SPE, King Abdullah University of Science and Technology. The paper has not been peer reviewed. Copyright 2021 International Petroleum Technology Conference. Reproduced by permission. Understanding the effect of microporosity on reservoir quality and predicting the spatial distribution of microporosity at the reservoir scale accurately is required to improve the recovery of remaining hydrocarbons from reservoirs. Using an integrated data-analysis approach applied to multiscale geological and geophysical data sets from micrometer-scale scanning-electron-microscope (SEM) imagery to decameter-scale seismic data, the authors predict the distribution of microporosity at the reservoir gridblock scale. The proposed methodology is applied in the complete paper to the Arab-D reservoir equivalent outcrop data from the Upper Jubaila formation in Saudi Arabia. Methodology This methodology is tested at an 800-m-long roadcut along the Riyadh-Mecca Highway in Saudi Arabia, stratigraphically equivalent to the Upper Jubaila Formation in the subsurface (Fig. 1). A 35-m-long core was drilled from the top of the same roadcut (dubbed the DQ-1 well), from which 106 cylindrical horizontal core plugs were obtained, drilled with an average spacing of 30 cm. This outcrop location was chosen because the pore volume in this interval is characterized by porosity with pore-diameter distribution of less than 10 µm. This outcrop provides an excellent analog to study microporosity-dominated carbonate rocks irrespective of their diagenetic origin. Moreover, the Upper Jubaila formation is a part of the Arab-D reservoir in the subsurface, which has been acclaimed as the most prolific oil reservoir in the world. Because this study used outcropped rocks, the authors acknowledge that differences in petrophysical properties with the subsurface rock formations will exist. Therefore, the study is not intended as a one-to-one analog for the Arab-D reservoir. Instead, the aim is to establish a general methodology that links micrometer-scale morphology of microcrystals that hosts microporosity with macroscale petrophysical properties and seismic attributes. Details of the methodology of seismic data acquisition and petrographic and petrophysical analysis are provided in the complete paper.
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MOURA, ANA CATARINA A., PAULO H. S. DE OLIVEIRA, JOAQUIM M. FERREIRA, FRANCISCO H. R. BEZERRA, REINHARDT A. FUCK i ADERSON F. DO NASCIMENTO. "Seismogenic faulting in the Meruoca granite, NE Brazil, consistent with a local weak fracture zone". Anais da Academia Brasileira de Ciências 86, nr 4 (grudzień 2014): 1631–39. http://dx.doi.org/10.1590/0001-3765201420130031.
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A sequence of earthquakes occurred in 2008 in the Meruoca granitic pluton, located in the northwestern part of the Borborema Province, NE Brazil. A seismological study defined the seismic activity occurring along the seismically-defined Riacho Fundo fault, a 081° striking, 8 km deep structure. The objective of this study was to analyze the correlation between this seismic activity and geological structures in the Meruoca granite. We carried out geological mapping in the epicentral area, analyzed the mineralogy of fault rocks, and compared the seismically-defined Riacho Fundo fault with geological data. We concluded that the seismically-defined fault coincides with ∼E–W-striking faults observed at outcrop scale and a swarm of Mesozoic basalt dikes. We propose that seismicity reactivated brittle structures in the Meruoca granite. Our study highlights the importance of geological mapping and mineralogical analysis in order to establish the relationships between geological structures and seismicity at a given area.
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Alaei, Behzad, i Anita Torabi. "Seismic imaging of fault damaged zone and its scaling relation with displacement". Interpretation 5, nr 4 (30.11.2017): SP83—SP93. http://dx.doi.org/10.1190/int-2016-0230.1.
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We have studied seismically resolved damaged zone of normal faults in siliciclastic rocks of the Norwegian continental shelf. The workflow we have developed reveals structural details of the fault damaged zone and in particular, the subsidiary synthetic faults, horsetail at the main lateral fault tips at different depths and fault bend. These subsidiary or small fault segments form an area that can be clearly followed laterally and vertically. We call this area fault damaged zone. The studied damaged zone on seismic data comprises the fault core and the fault damage zone, as defined in outcrop studies. Spectral decomposition (short-time Fourier transform for time-frequency resolution and continuous wavelet transform) was performed on the data centered around faulted intervals. The magnitude of higher frequencies was used to generate coherence attribute volumes. Coherence attributes were filtered to enhance fault images. This integrated workflow improves fault images on reflection seismic data. Our approach reveals details of damaged zone geometry and morphology, which are comparable with the outcrop studies of similar examples conducted by previous researchers or us. We have extracted the fault geometry data including the segment length, displacement, and damaged zone width at different depths. Our results show that subsidiary faults, fault bends, linkage of fault segments, and branching in the fault tip (horsetail structure or process zone) all affect the width of the damaged zone and the distribution of displacement. We have seen a distinct increase in the fault damaged zone width near the fault bend locations. The fault segment length decreases with depth toward the lower fault tip, which is below the base Cretaceous unconformity. In addition, the displacement increases below the unconformity. In general, there is a positive correlation between fault displacement and the corresponding damaged zone width measured in this study, which is in agreement with previous studies.
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Grech, P. V., i I. A. Dyson. "AN INTEGRATED APPROACH TO THE STUDY OF THE EARLY TRIASSIC REWAN GROUP, BOWEN BASIN". APPEA Journal 37, nr 1 (1997): 192. http://dx.doi.org/10.1071/aj96011.
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This study of the Early Triassic Rewan Group in the Bowen Basin was an integrated approach using seismic stratigraphic principles with outcrop, wireline log, bios- tratigraphy and core data. It resulted in a coherent and useable stratigraphic framework that assisted in defining facies and potential reservoirs below seismic resolution within the Rewan Group. The Rewan Group consists of the Sagittarius Sandstone and Arcadia Formation. Depositional systems of the Sagittarius Sandstone and Arcadia Formation were affected by major tectonic and climatic changes. Each formation is marked at its base by a third-order sequence boundary. The Sagittarius Sandstone is overall regressive and was deposited in a domi- nantly lacustrine environment. The base of the overlying Arcadia Formation is marked by the Brumby Sandstone Member. It was deposited in a fluvially dominated shoreface setting. Red beds of fluvial origin in the Arcadia Formation are characterised by overbank fines and lenticular channel sandstone. High-frequency incised valley fills occur in the uppermost Arcadia Formation. The Arcadia Formation is in turn erosively overlain by pebbly sandstone of the Clematis Group. Sandstone-filled incised valleys at the base of the Sagittarius Sandstone and in the upper Arcadia Formation offer the best reservoir potential in the Rewan Group.
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Pei, Yangwen, Douglas A. Paton, Rob J. Knipe, W. Henry Lickorish, Anren Li i Kongyou Wu. "Field-based investigation of fault architecture: A case study from the Lenghu fold-and-thrust belt, Qaidam Basin, NE Tibetan Plateau". GSA Bulletin 132, nr 1-2 (19.06.2019): 389–408. http://dx.doi.org/10.1130/b35140.1.
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AbstractThe fault zone architecture of a thrust fault zone is critical for understanding the strain accommodation and structural evolution in contractional systems. The fault architecture is also important for understanding fluid-flow behavior both along and/or across thrust fault zones and for evaluating potential fault-related compartmentalization. Because mesoscale (1–100 m) structural features are normally beyond seismic resolution, high-resolution outcrop in situ mapping (5–10 cm resolution) was employed to study the deformation features of a thrust fault zone located in the Qaidam Basin, northeastern Tibetan Plateau. The excellent exposure of outcrops enables the detailed investigation of the Lenghu thrust fault zone and its architecture. The Lenghu thrust fault, a seismically resolvable fault with up to ∼800 m of throw, exhibits a large variation of fault architecture and strain distribution along the fault zone. Multiple structural domains with different levels of strain were observed and are associated with the fault throw distribution across the fault. Based on previously proposed models and high-resolution outcrop mapping, an updated fault zone model was constructed to characterize the structural features and evolution of the Lenghu thrust. The possible parameters that impact fault architecture and strain distribution, including fault throw, bed thickness, lithology, and mechanical heterogeneity, were evaluated. Fault throw distributions and linkages control the strain distribution across a thrust fault zone, with local folding processes contributing important elements in Lenghu, especially where more incompetent beds dominate the stratigraphy. Mechanical heterogeneity, induced by different layer stacking patterns, controls the details of the fault architecture in the thrust zone. The variations in bed thicknesses and mechanical property contrasts are likely to control the initial fault dips and fault/fracture density. Large fault throws are associated with wide strain accommodation and damage zones, although the relationship between the development and width of the fault zone and the throw accumulation remains to be assessed. By presenting the high-resolution mapping of fault architecture, this study provides an insight into the subseismic fault zone geometry and strain distributions possible in thrust faults and reviews their application to assessments of fault zone behavior.
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TROCMÉ, VINCENT, EMILY ALBOUY, JEAN-PAUL CALLOT, JEAN LETOUZEY, NICOLAS ROLLAND, HASSAN GOODARZI i SALMAN JAHANI. "3D structural modelling of the southern Zagros fold-and-thrust belt diapiric province". Geological Magazine 148, nr 5-6 (5.08.2011): 879–900. http://dx.doi.org/10.1017/s0016756811000446.
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Abstract3D modelling of geological structures is a key method to improve the understanding of the geological history of an area, and to serve as a drive for exploration. Geomodelling has been performed on a large 60000 km2 area of the Zagros fold-and-thrust belt of Iran, to reconcile a vast but heterogeneous dataset. Topography, geological surface data and dips, outcrop surveys, and well and seismic data were integrated into the model. The method was to construct a key surface maximizing the hard data constraints. The Oligo-Miocene Top Asmari layer was chosen, as this formation was regionally deposited before the main Zagros collision phase and because the numerous outcrops allow proper control of the bed geometry in the fold cores. Interpreted seismic data have been integrated to interpolate the surfaces at depth within the synclines. Several conceptual models of fold geometry have been applied to estimate the best way to convert seismic time signal to depth. Several deeper horizons down to Palaeozoic strata were deduced from this key horizon by applying palaeo-thickness maps. During the construction, the 3D interpolated surfaces could be reconverted to time, using a velocity model, and compared with previous seismic interpretations. This exercise obliged us to revise some early interpretations of seismic lines that were badly tied to wells. The 3D modelling therefore clearly improves regional interpretation. In addition, the 3D model is the only tool that allows drawing consistent cross-sections in areas where there are no seismic lines. Emerging Hormuz salt diapirs were added to the model. Dimensions and shapes of the individual diapirs were modelled using a statistical survey on the cropping out Hormuz structures. Modelling reliably demonstrated that the diapirs, when piercing, show a constant mushroom shape whose diameter depends on the stratigraphic depth of observation. This observation allowed us to exemplify relations between the pre-existing diapirs and the anticlines of the area, and to highlight the morphological changes from the inner onshore areas to the coastal and offshore areas. In addition, one of the surprising results of this study was the observation of the increasing diameter of the diapirs at the time of the Zagros collision and folding event, with growth strata and overhangs on the flanks of the diapirs.
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Al-Fahmi, Mohammed, L. Cooke Michele i John C. Cole. "Modeling of the Dammam outcrop fractures: Case study for fracture development in salt-cored structures". GeoArabia 19, nr 1 (1.01.2014): 49–80. http://dx.doi.org/10.2113/geoarabia190149.
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ABSTRACT The exposed Cenozoic carbonates of the Dammam Dome are studied to: (1) characterize fractures and associated structures; (2) interpret the fracture mechanism; and (3) gain insights into fracture development within dome-like structures in the subsurface of the Arabian Gulf region. The fieldwork is integrated with structural analysis of the near-surface horizons mapped from interpretations of 3-D reflection seismic and borehole logs. Fractures are mapped from the outcrops of the middle limestone unit of the Eocene Rus Formation. The outcrops are concentrated in the central, northern and western areas of the Dammam Dome. The fractures are interpreted as opening-mode, bed-bounded joints that form orthogonal sets in most areas. The primary (older) joint set (J1) developed in long lineaments, some of which can be traced for over 300 m across entire exposures. The J1 set is found to be broadly consistent in its trend over the dome, indicating that formation of J1 fractures was systematic and not influenced by local structural anomalies (including karst collapse) formed during the Miocene to Recent. The trend of the J1 set does not correlate with the NE-SW compressional orientation of regional stresses associated with the Zagros Orogeny. Field data interpretation, allied with analysis of dome’s growth and curvature, suggest that the overall joint pattern reflects the growth of the strata as a dome. In addition, the joint density is controlled by structural position on the dome and mechanical stratigraphy. The study results provide a first-order conceptual fracture model for the subsurface reservoirs to guide future development.
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Lin, Song, Yuan Li, Denggui Luo i Yanlin Fu. "Research on the fracture structure and activity of the Qinling Mountains thrust nappe system in western Hubei". Canadian Journal of Earth Sciences 57, nr 1 (styczeń 2020): 1–15. http://dx.doi.org/10.1139/cjes-2018-0118.
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The Western Hubei section of the Liangyun fault is an important structural belt of the southern Qinling Mountains thrust nappe system. As the significant activity of the Liangyun fault since the Quaternary has led to high seismic risk in the surrounding area, the research on the characteristics and activity of fault structure is of great significance for deepening the construction of a seismic safety system in this area. In this study, we conducted a field geology survey combined with quartz optical stimulated luminescence dating, scanning electron microscopy dating, and thermoluminescence dating results and comprehensive application of shallow seismic reflection and high-resolution refraction) to analyze the activities of the Liangyun fault in the Quaternary period. Sediment optical stimulated luminescence dating results of samples from the breakpoint were 134.99 + 15.52 and 160.95 + 16.88 ka. Combined with the seismic profile, outcrop observation, and previous dating results, we conclude that the new era is in fault activities in the early Pleistocene to late Pleistocene (Q2–Q3). The combined application of shallow seismic reflection and high-resolution refraction method can confirm each other’s measured results, providing more parameters for the interpretation of seismic data under complex conditions and ensuring the accuracy of data interpretation at the same time. At present, the seismic experiment scheme is less used in the field of active fault detection, since its good detection effect and the application of the trial to shallow geophysical exploration has a certain application value and global scalability.
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Wu, Wei-Jhe, Chien-Min Su i Chau-Huei Chen. "The Investigation of Shallow Structures at the Meishan Fault Zone with Ambient Noise Tomography Using a Dense Array Data". Applied Sciences 12, nr 12 (8.06.2022): 5847. http://dx.doi.org/10.3390/app12125847.
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Seismic monitoring relies on seismography. However, the high cost of seismic equipment has presented a challenge to increasing the density of seismic networks in previous decades. Due to the large station spacing and inferior coverage of stations, this situation has led to a loss of detail in many research results. Along with the improvement of technology, the problem of increasing the density of seismographic observations is no longer an impossible issue. This makes it feasible to deploy a dense seismic network for monitoring earthquakes. This study deployed a linear dense array across the Meishan Fault in west-southern Taiwan for the purpose of analyzing the shallow fault zone structure. While the 1906 Meishan earthquake occurred in a period when historic records were available, the surficial geology surveys of the Meishan Fault are challenging because farming and construction engineering have obscured the outcrop. Early surveys of the Meishan Fault were mainly seismic surveys. In recent decades, over thirty profiles have been completed. However, the reflection seismic records had poor signal-to-noise ratios because the Meishan Fault is buried under thick sediments. Thus, the shallow structure of the Meishan Fault is still not known in detail. This study applied double-beamforming tomography to a dense seismic array to obtain high-resolution images of the Meishan Fault zone. The result shows that there is a south-dipping interface near the fault trace as indicated by the Central Geological Survey of Taiwan. In addition, we observed velocity transitions of perturbation profiles that may be caused by a branch fault, the Chentsoliao Fault. This study demonstrates that the ambient noise double beamforming method is an effective tool for imaging the detailed shallow structure along with the dense seismic array.
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Ramli, Taufik, M. Heri Hermiyanto Z i Andy Setyo Wibowo. "SHALE GAS SWEET SPOT POTENTIAL OF TUNGKAL GRABEN, JAMBI SUB-BASIN SOUTH SUMATERA BASIN". Scientific Contributions Oil and Gas 42, nr 3 (11.12.2019): 109–14. http://dx.doi.org/10.29017/scog.42.3.397.
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The Tungkal Graben is located in Jambi Sub-basin, the northern part of South Sumatera Basin. This basin is known as one of the largest hydrocarbons producing basin in Indonesia. There are several proven source rocks in the South Sumatera Basin. The paralic shales and coal horizon of Talangakar Formation (TAF) are known as primary source rock in this basin and considered as a reservoir of shale gas-bearing in Tungkal Graben Area as well. This study used surface geological data that was collected from the southern foot of Tiga Puluh Mountain as the outcrop analogy and subsurface data (existing well and seismic data) in Tungkal Graben Area. This study applied integrated methods including environmental deposition analysis, organic geochemistry analysis, petrophysical analysis, seismic interpretation, sweet spot delineation, and volumetric of gas in place (GIP) calculation. TAF observed both on the outcrop and well is transition deposit that consists of the dominance of shale and siltstone with interbedded of coal, sandstone, and limestone. Shale and siltstone of TAF have characteristic which is appropriate as a shale gas bearing, with sufficient organic content richness, suitable kerogen type, its maturity entering the early gas generation and proper brittleness index (BI). The sweet spot area is an area that has met the criteria for potential shale gas and determined by pay zone criteria. Depend on the criteria, Net to gross for shale gas is 0.158, early gas generation estimated at a depth of 10250 feet, and sweet spot area reaches 8.9 x 108 ft2. Thus, the total potential of shale gas resources from the calculation using the Ambrose method is 2.12 TCF.
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Tari, Gábor Csaba, Viktória Németh, Ferenc Horváth † i Viktor Wesztergom. "A regional Alpine graphite décollement level beneath the NW Pannonian Basin". Földtani Közlöny 149, nr 3 (29.09.2019): 279. http://dx.doi.org/10.23928/foldt.kozl.2019.149.3.279.
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The so-called Transdanubian Conductivity Anomaly (TCA) of the Hungarian part of the NW Pannonian Basin has been well known for more than five decades. The exceptionally low resistivity (i.e. 1–2 Ωm) zone has a very large areal extent (on the order a few thousand km2) and it is an entirely subsurface anomaly occurring at depth between circa 3–15 km, with no corresponding outcrops. Various geological explanations of this enigmatic crustal-scale geophysical anomaly range from invoking sub-horizontal Alpine nappe contacts to sub-vertical dikes with graphite and/or saline fluid content. Only one possible analogue outcrop area was considered for the high conductivity anomaly so far, namely the Drauzug/Gailtal area of the Eastern Alps in Austria, some 300 km to the West from the TCA area. Previous attempts to find correspondence between the TCA and prominent seismic reflectors seen on 2D seismic reflection profiles were based on data acquired by research institutions. This study systematically correlates, for the first time, the TCA with 2D industry seismic reflection data in the same area. Our new results show a very strong correlation between the subsurface extent and location of the TCA with various sub-horizontally oriented Cretaceous Alpine nappe surfaces. In addition, we draw on the latest structural correlation of the Alpine nappe stack of the Transdanubian Range with its proper tectonic counterpart in the Eastern Alps.At the southern edge of the Upper Austroalpine units in northern Styria, in the Veitsch Nappe of the Greywacke Zone, numerous graphite localities are known historically. These laterally extensive graphite units in NW Styria formed as the result of greenschist-grade metamorphism of a Carboniferous coal sequence during the Cretaceous. For the first time, we describe here one well penetration of possibly age-equivalent graphitic units in NW Hungary. Correlation of the magnetotelluric anomaly with the distinct reflection seismic signature suggests that the same Palaeozoic graphitebearing Upper Austroalpine units should be present at 3–15 km depth in our study area.Therefore we propose that the best explanation for the observed extent and geometry of the TCA is the presence of graphite in subhorizontal, tectonically thinned detachment surfaces at the base of the Upper Austroalpine nappe edifice of NW Hungary
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Schofield, Nick, Richard Newton, Scott Thackrey, Douglas Watson, David Jolley i Chris Morley. "Linking surface and subsurface volcanic stratigraphy in the Turkana Depression of the East African Rift system". Journal of the Geological Society 178, nr 1 (11.09.2020): jgs2020–110. http://dx.doi.org/10.1144/jgs2020-110.
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The Northern Kenya Rift is an important natural laboratory for understanding continental rifting processes. However, much of the current understanding of its geological evolution is based on surface outcrops within footwall highs due to a lack of subsurface geological constraints. In this paper, we present an investigation of the Cenozoic stratigraphy and volcano-tectonic relationship of the volcanic sequences within the Turkana Depression (namely the North Lokichar, North Kerio and Turkana Basins). We integrate regional seismic reflection data collected as part of ongoing petroleum exploration in the area with lithological and biostratigraphic data from new wells that were drilled in 2014 and 2015 (Epir-1 and Emesek-1). This has allowed linking and extrapolation of the detailed stratigraphy of the paleontologically important Lothagam site to the volcanic sequences within the Napedet Hills, North Lokichar, North Kerio and Turkana Basins. The site of the Plio-Pleistocene-age Turkana Fault, which separates the North Lokichar Basin from the Turkana and North Kerio Basins, appears previously to have acted as a focus of Middle Miocene volcanism c. 5 Ma prior to the main period of movement on the fault. Our study highlights how subsurface and outcrop information can be combined to give a more in-depth knowledge of the magmatic history within rift basins.
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Bartha, István Róbert, Dániel Botka, Vivien Csoma, Lajos Tamás Katona, Emőke Tóth, Imre Magyar, Lóránd Silye i Orsolya Sztanó. "From marginal outcrops to basin interior: a new perspective on the sedimentary evolution of the eastern Pannonian Basin". International Journal of Earth Sciences 111, nr 1 (30.10.2021): 335–57. http://dx.doi.org/10.1007/s00531-021-02117-6.
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AbstractSedimentary successions exposed at basin margins as a result of late-stage inversion, uplift and erosion usually represent only a limited portion of the entire basin fill; thus, they are highly incomplete records of basin evolution. Small satellite basins, however, might have the potential of recording more complete histories. The late Miocene sedimentary history of the Șimleu Basin, a north-eastern satellite of the vast Pannonian Basin, was investigated through the study of large outcrops and correlative well-logs. A full transgressive–regressive cycle is reconstructed, which formed within a ca. 1 million-year time frame (10.6–9.6 Ma). The transgressive phase is represented by coarse-grained deltas overlain by deep-water lacustrine marls. Onset of the regressive phase is indicated by sandy turbidite lobes and channels, followed by slope shales, and topped by stacked deltaic lobes and fluvial deposits. The deep- to shallow-water sedimentary facies are similar to those deposited in the central, deep part of the Pannonian Basin. The Șimleu Basin is thus a close and almost complete outcrop analogue of the Pannonian Basin’s lacustrine sedimentary record known mainly from subsurface data, such as well-logs, cores and seismic sections from the basin interior. This study demonstrates that deposits of small satellite basins may reflect the whole sequence of processes that shaped the major basin, although at a smaller spatial and temporal scale.
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Kagami, Hiroshi, Shigeyuki Okada, Keishi Shiono, Mete Oner, Marijan Dravinski i Ajit K. Mal. "Observation of 1- to 5-second microtremors and their application to earthquake engineering. Part III. A two-dimensional study of site effects in the San Fernando Valley". Bulletin of the Seismological Society of America 76, nr 6 (1.12.1986): 1801–12. http://dx.doi.org/10.1785/bssa0760061801.
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Abstract A two-dimensional study of the influence of deep sediment on seismic ground motions was conducted by recording and analyzing long-period microtremors in the San Fernando Valley, California. The recordings were made at 50 regularly distributed sites in the valley. Three reference sites were employed at the baserock outcrop around the valley so as to observe the time-dependent characteristics of the microtremors. Amplitudes in a period range of several seconds correlate with the thicknesses of the sedimentary layers. A site amplification effect, which was evaluated in terms of sediment-to-rock spectral ratios, is qualitatively consistent with available geological and strong motion data. The practical field observation procedure designed for this study, the two-dimensional approach, can be easily used in other surveys for estimating the spatial characteristics of earthquake ground motions in the period range of several seconds.
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de Franco, R., L. Petracchini, D. Scrocca, G. Caielli, G. Montegrossi, A. Santilano i A. Manzella. "Synthetic Seismic Reflection Modelling in a Supercritical Geothermal System: An Image of the K-Horizon in the Larderello Field (Italy)". Geofluids 2019 (28.03.2019): 1–21. http://dx.doi.org/10.1155/2019/8492453.
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We tested synthetic seismic reflection modelling along a seismic line (CROP-18A) in the geothermal field at Larderello (Italy). This seismic line is characterized by a discontinuous but locally very bright seismic marker, named K-horizon, which has been associated with various geological processes, including the presence of fluids at supercritical conditions. Geological and geophysical data were integrated in order to develop a 3D subsurface model of a portion of the Larderello field, where extremely high heat flow values have been recorded. In the study area, the K-horizon is particularly shallow and supercritical deep conditions were accessed at depth. The 2D model of the main geological units up to the K-horizon was extracted from the 3D model along the CROP-18A and used to generate the synthetic TWT stacked seismic sections which were then compared with the observed stacked CROP-18A seismic section. To build the synthetic sections, generated through the exploding reflector approach, a 2D velocity model was created assigning to each pixel of the model a constant P-wave velocity corresponding to the related geological unit. The geophysical parameters and the geological model reconstructions used in the modelling process derive from a multidisciplinary integration process including geological outcrop analogues, core samples, and geophysical and laboratory information. Two geophysical models were used to test the seismic response of the K-horizon, which is associated with (1) a lithological discontinuity or (2) a physically perturbed layer, represented by a randomized velocity distribution in a thin layer. For the latter geophysical model (i.e., the physically perturbed layer), we have tested three different scenarios changing the shape and the thickness of the modelled layer. Despite the reliable calibration implied by the use of homogeneous units, the seismic modelling clearly shows that the physically perturbed layer provides a better explanation of the reflectivity features associated with the K-horizon.
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Maurizio, Ercoli, Pauselli Cristina, Romana Cinti Francesca, Forte Emanuele i Volpe Roberto. "Imaging of an active fault: Comparison between 3D GPR data and outcrops at the Castrovillari fault, Calabria, Italy". Interpretation 3, nr 3 (1.08.2015): SY57—SY66. http://dx.doi.org/10.1190/int-2014-0234.1.
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We have integrated and analyzed a 3D ground-penetrating radar (GPR) volume with a trenching exposure data set to evaluate the potential of these methods individually and combined for study of a fault zone. We chose a test site across a branch of the active Castrovillari fault in the Northern Calabria (Southern Italy). This tectonic structure is one of the most active in the area, and it has generated strong earthquakes in the past. Based on analysis of previously collected data, a 3D GPR survey was carried out 1.2 m from a fault outcrop. The goal was to use the GPR volume to guide and optimize the excavation of a trench and then to use the trenching data to validate the GPR volume interpretation. We used seismic interpretation software to display vertical and horizontal sections and for horizon tracking and attribute analyses. We obtained quantitative information on the geometry of structural and geologic features, such as fault strike and dip angle, defining the boundaries of different stratigraphic units. We validated our GPR data interpretation with the outcrop section and trench wall demonstrating the benefits of GPR in extensional tectonics environments and the great potential of the combined geologic and geophysical approach.
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Stepp, J. Carl, Ivan Wong, John Whitney, Richard Quittmeyer, Norman Abrahamson, Gabriel Toro, Robert Youngs, Kevin Coppersmith, Jean Savy i Tim Sullivan. "Probabilistic Seismic Hazard Analyses for Ground Motions and Fault Displacement at Yucca Mountain, Nevada". Earthquake Spectra 17, nr 1 (luty 2001): 113–51. http://dx.doi.org/10.1193/1.1586169.
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Probabilistic seismic hazard analyses were conducted to estimate both ground motion and fault displacement hazards at the potential geologic repository for spent nuclear fuel and high-level radioactive waste at Yucca Mountain, Nevada. The study is believed to be the largest and most comprehensive analyses ever conducted for ground-shaking hazard and is a first-of-a-kind assessment of probabilistic fault displacement hazard. The major emphasis of the study was on the quantification of epistemic uncertainty. Six teams of three experts performed seismic source and fault displacement evaluations, and seven individual experts provided ground motion evaluations. State-of-the-practice expert elicitation processes involving structured workshops, consensus identification of parameters and issues to be evaluated, common sharing of data and information, and open exchanges about the basis for preliminary interpretations were implemented. Ground-shaking hazard was computed for a hypothetical rock outcrop at -300 m, the depth of the potential waste emplacement drifts, at the designated design annual exceedance probabilities of 10-3 and 10-4. The fault displacement hazard was calculated at the design annual exceedance probabilities of 10-4 and 10-5.
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Burberry, Caroline M., R. M. Joeckel i Jesse T. Korus. "Post-Mississippian tectonic evolution of the Nemaha Tectonic Zone and Midcontinent Rift System, SE Nebraska and N Kansas". Mountain Geologist 52, nr 4 (1.10.2015): 47–73. http://dx.doi.org/10.31582/rmag.mg.52.4.47.
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The geologic structures of the central Midcontinent of the USA are largely buried and known only from geophysical datasets, coupled with sparse well control and limited outcrop. Such unconstrained geophysical models preclude a deeper assessment of possible continental interior seismic hazards, which have the potential to cause appreciable damage. Within the study area in southeastern Nebraska and northeastern Kansas is an area of elevated seismic risk, with a spatial relationship to the Nemaha Tectonic Zone and the Midcontinent Rift System. Using sequential restorations of three published cross sections within Nebraska and Kansas this study demonstrates that the Nemaha Tectonic Zone and Midcontinent Rift System have each been reactivated several times since the end of the Mississippian (the details of deformation prior to the Mississippian are not considered). Our reconstructions indicate that in addition to major Pennsylvanian-Early Permian fault reactivation during the Ancestral Rocky Mountain orogeny there was also deformation both prior to the post-Mississippian unconformity associated with uplift on the Nemaha Tectonic Zone and after the deposition of late Early-early Late Cretaceous sediments in the study area, potentially due to the Laramide orogeny. Results also indicate that the magnitude of the far-field stresses is sufficient to cause seismogenic reactivation on favorably oriented pre-existing faults. This history of reactivation of geologic structures in the central Midcontinent suggests that seismic hazards in the region in the present cannot be ruled out. Though dangerous large earthquakes are uncommon in the continental interior, seismic activity along the structures in the study area would threaten several large population centers and the potential for this activity should not be ignored.
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Burhannudinnur, M., i C. K. Morley. "Anatomy of growth fault zones in poorly lithified sandstones and shales; implications for reservoir studies and seismic interpretation; Part 1, Outcrop study". Petroleum Geoscience 3, nr 3 (wrzesień 1997): 211–24. http://dx.doi.org/10.1144/petgeo.3.3.211.
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Caf, Abidin B., i John D. Pigott. "Dolomitization geometry and reservoir quality from supervised Bayesian classification and probabilistic neural networks: Midland Basin Leonardian Wichita and Clear Fork Formations". Interpretation 9, nr 2 (22.04.2021): T585—T598. http://dx.doi.org/10.1190/int-2020-0204.1.
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Extensive dolomitization is prevalent in the platform and periplatform carbonates in the Lower-Middle Permian strata in the Midland and greater Permian Basin. Early workers have found that the platform and shelf-top carbonates were dolomitized, whereas slope and basinal carbonates remained calcitic, proposing a reflux dolomitization model as the possible diagenetic mechanism. More importantly, they underline that this dolomitization pattern controls the porosity and forms an updip seal. These studies are predominately conducted using well logs, cores, and outcrop analogs, and although exhibiting high resolution vertically, such determinations are laterally sparse. We have used supervised Bayesian classification and probabilistic neural networks (PNN) on a 3D seismic volume to create an estimation of the most probable distribution of dolomite and limestone within a subsurface 3D volume petrophysically constrained. Combining this lithologic information with porosity, we then illuminate the diagenetic effects on a seismic scale. We started our workflow by deriving lithology classifications from well-log crossplots of neutron porosity and acoustic impedance to determine the a priori proportions of the lithology and the probability density functions calculation for each lithology type. Then, we applied these probability distributions and a priori proportions to 3D seismic volumes of the acoustic impedance and predicted neutron porosity volume to create a lithology volume and probability volumes for each lithology type. The acoustic impedance volume was obtained by model-based poststack inversion, and the neutron porosity volume was obtained by the PNN. Our results best supported a regional reflux dolomitization model, in which the porosity is increasing from shelf to slope while the dolomitization is decreasing, but with sea-level forcing. With this study, we determined that diagenesis and the corresponding reservoir quality in these platforms and periplatform strata can be directly imaged and mapped on a seismic scale by quantitative seismic interpretation and supervised classification methods.
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Dixit, Nilesh C., i Catherine Hanks. "Basement Structure and Styles of Active Tectonic Deformation in Central Interior Alaska". Geosciences 11, nr 3 (10.03.2021): 127. http://dx.doi.org/10.3390/geosciences11030127.
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Central Interior Alaska is one of the most seismically active regions in North America, exhibiting a high concentration of intraplate earthquakes approximately 700 km away from the southern Alaska subduction zone. Seismological evidence suggests that intraplate seismicity in the region is not uniformly distributed, but concentrated in several discrete seismic zones, including the Nenana basin and the adjacent Tanana basin. Although the location and magnitude of the seismic activity in both basins are well defined by a network of seismic stations in the region, the tectonic controls on these intraplate earthquakes and the heterogeneous nature of Alaska’s continental interior remain poorly understood. We investigated the crustal structure of the Nenana and Tanana basins using available seismic reflection, aeromagnetic and gravity anomaly data, supplemented by geophysical well logs and outcrop data. We developed nine new two-dimensional forward models to delineate internal geometries and the crustal structure of Alaska’s interior. The results of our study demonstrates a strong crustal heterogeneity beneath both basins. The Tanana basin is a relatively shallow (up to 2 km) asymmetrical foreland basin with its southern, deeper side controlled by the northern foothills of the Central Alaska Range. Northeast-trending left lateral strike-slip faults within the Tanana basin are interpreted as a zone of clockwise crustal block rotation. The Nenana basin has a fundamentally different geometry. It is a deep (up to 8 km), narrow transtensional pull-apart basin that is deforming along the left-lateral Minto Fault. This study identifies two distinct modes of current tectonic deformation in Central Interior Alaska and provides a basis for modeling the interplay between intraplate stress fields and major structural features that potentially influence the generation of intraplate earthquakes in the region.
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Lyu, Bin, Qin Su i Kurt J. Marfurt. "Tomographic velocity analysis and wave-equation depth migration in an overthrust terrain: A case study from the Tuha Basin, China". Interpretation 6, nr 1 (1.02.2018): T1—T13. http://dx.doi.org/10.1190/int-2017-0053.1.
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Although the structures associated with overthrust terrains form important targets in many basins, accurately imaging remains challenging. Steep dips and strong lateral velocity variations associated with these complex structures require prestack depth migration instead of simpler time migration. The associated rough topography, coupled with older, more indurated, and thus high-velocity rocks near or outcropping at the surface often lead to seismic data that suffer from severe statics problems, strong head waves, and backscattered energy from the shallow section, giving rise to a low signal-to-noise ratio that increases the difficulties in building an accurate velocity model for subsequent depth migration. We applied a multidomain cascaded noise attenuation workflow to suppress much of the linear noise. Strong lateral velocity variations occur not only at depth but near the surface as well, distorting the reflections and degrading all deeper images. Conventional elevation corrections followed by refraction statics methods fail in these areas due to poor data quality and the absence of a continuous refracting surface. Although a seismically derived tomographic solution provides an improved image, constraining the solution to the near-surface depth-domain interval velocities measured along the surface outcrop data provides further improvement. Although a one-way wave-equation migration algorithm accounts for the strong lateral velocity variations and complicated structures at depth, modifying the algorithm to account for lateral variation in illumination caused by the irregular topography significantly improves the image, preserving the subsurface amplitude variations. We believe that our step-by-step workflow of addressing the data quality, velocity model building, and seismic imaging developed for the Tuha Basin of China can be applied to other overthrust plays in other parts of the world.
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Tempa, Karma, Komal Raj Aryal, Nimesh Chettri, Giovanni Forte i Dipendra Gautam. "Sensitivity analysis of input ground motion on surface motion parameters in high seismic regions: a case of Bhutan Himalaya". Natural Hazards and Earth System Sciences 22, nr 6 (7.06.2022): 1893–909. http://dx.doi.org/10.5194/nhess-22-1893-2022.
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Abstract. Historical earthquakes demonstrate that strong motion characteristics and local soil condition, when coupled, significantly influence seismic site response. Interestingly, most of the Himalayan earthquakes depicted anomalous behavior per the site conditions historically. Being one of the most active seismic regions on earth, the eastern fringe of the Himalaya has observed many devastating earthquakes together with non-uniform damage scenarios. To quantify such anomalies, we evaluate surface motion parameters for a soft soil deposit located in the city of Phuentsholing in western Bhutan. Using one-dimensional site response analysis, the sensitivity of ground motion variation is estimated. This study accounts for the earthquakes of moment magnitudes 6.6 to 7.5 with a wide variation in peak ground acceleration (PGA). To dissect the characteristics of six inputted ground motions on eight local ground conditions, a sensitivity analysis is performed statistically. The statistical correlation of the response datasets and the linear regression model of the bedrock outcrop and the surface motion spectral acceleration along the stratified depth are examined to quantify the variation in surface motion parameters. The results highlight that the strong motions with PGA greater than 0.34 g demonstrate greater sensitivity, leading to some anomalies in response parameters, especially amplification. Similar results were obtained for the low PGA range (<0.1 g).
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Rasmussen, Erik S., Karen Dybkjær i Stefan Piasecki. "The Billund delta: a possible new giant aquifer in central and western Jutland". Geological Survey of Denmark and Greenland (GEUS) Bulletin 4 (20.07.2004): 21–24. http://dx.doi.org/10.34194/geusb.v4.4773.
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The search for new, deep-seated drinking water resources in Denmark has increased significantly during the past five years as a result of the discovery of excessive amounts of nitrate, pesticides and other pollutants in shallow groundwater boreholes (e.g. Nygaard et al. 2004, this volume). To find and map these aquifers, a multidisciplinary sequence stratigraphic approach has successfully been applied to the Miocene deposits of southern Jutland, where especially the Odderup and Ribe Formations are known as a main aquifer for drinking water from several test wells (Rasmussen et al. 2002). Recently, a more systematic study of the Miocene succession in central and western Jutland has been initiated by the Geological Survey of Denmark and Greenland (GEUS) under contract with local authorities. It includes detailed sedimentological descriptions of outcrops, sedimentological andlog-interpretations of new stratigraphic boreholes and interpretation of new high-resolution seismic data (Fig. 1). A number of outcrops and wells have been studied palynologically, resulting in a detailed dinoflagellate cyst stratigraphy and in palynofacies interpretations. The results of these studies have been integrated in the regional geological and stratigraphic model (Fig. 2). Two new aquifers have been discovered: the Bastrup sand and the Billund sand. The Bastrup sand has already been exploited as a main aquifer in central and southern Jutland, and has been referred to either the Ribe or Odderup Formations. However, new stratigraphic results reveal that the Bastrup sand is a separate unit in the Miocene succession. The Billund sand is a deep-seated aquifer located more than 100 m and often more than 150 m deep, and is therefore not penetrated by standard water supply wells which rarely reach c. 100 m. The Billund sand was first revealed by multichannel seismic data deriving from former oil-exploration carried out in the Billund area (Fig. 3A). The resolution of these seismic data is very poor, but one interpretation of the dipping reflectors (clinoforms) seen in Fig. 3A was of a delta complex. This agrees with outcrop studies along the fjords of eastern Jutland which suggest that a spit complex was deposited in this area during the Early Miocene. The Billund sand was tested by the Vandel Mark well in 2001, which penetrated c. 40 m of sand at a depth of 200 m. The presence of a regional major sand body was later confirmed by new high-resolution seismic data and by the Billund and Løvlund wells in 2002. The Billund well penetrated 50 m of medium- to coarse-grained sand, and chemical tests of the water quality were good. However, a water supply well at Fjand in western Jutland has had problems with so-called ‘brown water’ – water enriched in organic matter (humus). Saline water may also be expected close to older deep-seated faults. This paper summarises the results of a mapping programme of the Billund sand initiated in the summer of 2003.
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Larsen, Michael, Brian Bell, Pierpaolo Guarnieri, Henrik Vosgerau i Rikke Weibel. "Exploration challenges along the North Atlantic volcanic margins: the intra-volcanic sandstone play in subsurface and outcrop". Geological Society, London, Petroleum Geology Conference series 8, nr 1 (27.10.2016): 231–45. http://dx.doi.org/10.1144/pgc8.13.
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AbstractThe margins of the North Atlantic rift are covered by an extensive succession of volcanic rocks, with up to 5 km of continental flood basalts, hyaloclastites and interbedded sedimentary rocks. The volcanic succession deteriorates seismic imaging and has hampered petroleum exploration in these areas. Focused research and pioneering exploration activity, however, has improved the understanding and development of new play models in volcanic-influenced basins. In 2004, the Rosebank discovery finally proved that intra-volcanic siliciclastic sandstones of the Flett Formation may form attractive hydrocarbon reservoirs in the Faroe–Shetland Basin.The Kangerlussuaq Basin in southern East Greenland offers a unique opportunity to study the interaction of siliciclastic sediments with lavas and various volcaniclastic units. It is demonstrated that: (1) laterally extensive siliciclastic sedimentary units are present in the lower part of the volcanic succession; (2) the morphology of the lavas controlled variations in sandstone geometry and thickness; and (3) deposition of the interbedded sediments and lavas occurred in a low-relief environment close to sea level. The mineralogical composition of the intra-volcanic sediments is highly variable, ranging from siliciclastic to purely volcaniclastic. Diagenetic studies suggest that the nature of the volcanic component in volcaniclastic sandstones is more important to reservoir properties than the relative concentration.
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Kolyukhin, Dmitriy, Anita Torabi, Audun Libak, Behzad Alaei i Tatiana Khachkova. "Statistical Analysis of Displacement and Length Relation for Normal Faults in the Barents Sea". Geosciences 8, nr 11 (14.11.2018): 421. http://dx.doi.org/10.3390/geosciences8110421.
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This paper is devoted to the statistical analysis of dependence between fault length (L) and displacement (D). The main purpose of this work is to study the scaling relations between fault length and displacement using a database that includes datasets of 21 faults with geometric data extracted from 3D seismic coherence cubes of the Norwegian Barents Sea. Multiple linear regression and Bayesian and Akaike information criterions are applied to obtain optimal regression parameters. Our dataset is unique since it includes segment lengths of individual faults, unlike the previously published datasets. Hence, we studied both the dependence of fault segment length and accumulated fault length on displacement. The latter relation (accumulated fault length versus displacement) shows a general agreement (positive correlation and power-law relation) with the previously published results that are mainly obtained from outcrop studies, although the slopes vary for different lithologies. The differences could be attributed to the unique characteristics of our dataset that includes data of all segment lengths of individual faults.
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Xia, Zhao Hui, Ming Zhang, Bin Ren, Liang Chao Qu, Ze Hong Cui, Ling Li Liu, Yong Yang i Shuang Zhen Cao. "Important Factors to Propose High-Produced New Development Wells in CBM Project". Advanced Materials Research 1030-1032 (wrzesień 2014): 2578–81. http://dx.doi.org/10.4028/www.scientific.net/amr.1030-1032.2578.
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Coal bed methane (CBM) is a kind of natural gas that generated from coal and disseminated organic matters during the stage of diagenesis and coalification, which mainly composed of methane and hosted in coal seam by free, adsorbed, and dissolved forms. Genetic, reservoir type and occurrence condition in CBM are different from traditional reservoir. And the high-produced development wells in CBM aiming to drill more coal seams with high quality therefore needs to be analyzed in the methods that are different from traditional reservoir. 3 important factors including the study on correlation and elevation depth of coal seam roof and floor in section and areal by using well-seismic ties, outcrop boundary based on coal mine data and distributions of CBM reservoir properties in 3D model are needed for high-produced development well analyze in CBM. Application in Australia CBM project shows this methodology is very successful for the development well design with high production.
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Burgin, Hugo B., Khalid Amrouch, Mojtaba Rajabi, David Kulikowski i Simon P. Holford. "Determining paleo-structural environments through natural fracture and calcite twin analyses: a case study in the Otway Basin, Australia". APPEA Journal 58, nr 1 (2018): 238. http://dx.doi.org/10.1071/aj17099.
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The structural history of the Otway Basin has been widely studied; however, previous works have focussed on large kilometre scale, basin and seismic structures, or have over-simplified natural fracture analysis with an excessive focus on fracture strike direction and a disregard for 3D geometry, a crucial characteristic when considering states of stress responsible for natural fracture formation. In this paper, we combine techniques of natural fracture analysis and calcite twin stress inversion to investigate the meso (outcrop and borehole) and micro (crystal) scale evidence for structural environments that have contributed to basin evolution. Our results indicate that basin evolution during the post-Albian may be markedly more complex than the previously thought stages of late Cretaceous inversion, renewed rifting and long-lived mid-Eocene to recent compression, with evidence for up to six structural environments detected across the basin, including; NE–SW and NW–SE extension, NW–SE compression, a previously undetected regime of NE–SW compression, and two regimes of strike-slip activity. By constraining structural environments on the meso- and micro-scale we can deliver higher levels of detail into structural evolution, which in turn, provides better-quality insights into multiple petroleum system elements, including secondary migration pathways and trap formation. Our research also shows that the Otway Basin presents a suitable environment for additional micro-scale structural investigations through calcite twin analyses.
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Siregar, Rahmat Nawi, Maria Evalina Purba i Ahmat Munawir Siregar. "Analisa Produksi Panas Radiogenik, Densitas dan Kecepatan Seismik dari Singkapan Batu Granit Panas Bumi Nyelanding, Bangka Selatan". Science, and Physics Education Journal (SPEJ) 3, nr 2 (29.06.2020): 103–12. http://dx.doi.org/10.31539/spej.v3i2.1151.
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The purpose of this study was to determine the analysis of radiogenic heat production, density and seismic velocity of the outcrops of the South Bangka Nyelanding geothermal rock. The X-ray Fluorescence (XRF) method is applied to obtain heat-carrying radioactive elements in the form of Uranium, Thorium and Potassium and other oxides which are useful for studying seismic density and velocity. The main oxides used in this study were SiO2, TiO2, Al2O3, MgO, CaO, K2O and P2O5. The results showed that the density increased from the composition of the mineral felsic (acid) - mafic (base). Conclusion, as for the relationship with heat production, the SiO2 and P2O5 elements experienced a significant decrease compared to other oxides. As for seismic velocity, the results show that seismic velocity has a strong correlation with density.
Keywords: Radiogenic Heat Production, Seismic Velocity, Density, Oxides
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Berry, M. D., D. W. Stearns i M. Friedman. "THE DEVELOPMENT OF A FRACTURED RESERVOIR MODEL FOR THE PALM VALLEY GAS FIELD". APPEA Journal 36, nr 1 (1996): 82. http://dx.doi.org/10.1071/aj95005.
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A fractured reservoir model has been developed for the Palm Valley gas field, located WSW of Alice Springs, in the Amadeus Basin, NT. Definition of this complex, naturally fractured, Ordovician gas reservoir has required an integrated approach involving multiple studies to develop the geological model that has formed the basis for reservoir simulation and the rationale for the location of new wells. In addition, new seismic data provided fundamental input to the structure/fracture model of the field. Results suggest a primary, northsouth compression for the origin of structures in the basin and that Palm Valley resulted from a single, balanced folding phase. The seismic data show that Palm Valley is not an arcuate anticline as previously mapped, but is an elongate WSW to ENE trending, doubly plunging anticline with an offset crest and minor reverse faults at reservoir level. Investigations have shown that the majority of fractures in the reservoir outcrop are extremely ordered and there is definite structural control of the fracture spacing in the brittle reservoir rocks. Fracture trajectory and fracture intensity maps have been constructed, the latter providing the mechanism for distribution of fracture parameters around the field. The orientation of fractures measured at depth in the reservoir match exactly the fractures predicted from the structure/fracture model. This is the first time a fractured reservoir model that has been developed for Palm Valley, and it will form the basis for the further study and future development of the field.
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Jonoud, S., O. P. P. Wennberg, G. Casini i J. A. A. Larsen. "Capturing the Effect of Fracture Heterogeneity on Multiphase Flow During Fluid Injection". SPE Reservoir Evaluation & Engineering 16, nr 02 (8.05.2013): 194–208. http://dx.doi.org/10.2118/147834-pa.
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Summary Carbonate fractured reservoirs introduce a tremendous challenge to the upscaling of both single- and multiphase flow. The complexity comes from both heterogeneous matrix and fracture systems in which the separation of scales is very difficult. The mathematical upscaling techniques, derived from representative elementary volume (REV), must therefore be replaced by a more realistic geology-based approach. In the case of multiphase flow, an evaluation of the main forces acting during oil recovery must also be performed. A matrix-sector model from a highly heterogeneous carbonate reservoir is linked to different fracture realizations in dual-continuum simulations. An integrated iterative workflow between the geology-based static modeling and the dynamic simulations is used to investigate the effect of fracture heterogeneity on multiphase fluid flow. Heterogeneities at various scales (i.e., diffuse fractures and subseismic faults) are considered. The diffuse-fracture model is built on the basis of facies and porosity from the matrix model together with core data, image-log data, and data from outcrop-analogs. Because of poor seismic data, the subseismic-fault model is mainly conceptual and is based on the analysis of outcrop-analog data. Fluid-flow simulations are run for both single-phase and multiphase flow and gas and water injections. A better understanding of fractured-reservoirs behavior is achieved by incorporating realistic fracture heterogeneity into the geological model and analyzing the dynamic impact of fractures at various scales. In the case of diffuse fractures, the heterogeneity effect can be captured in the upscaled model. The subseismic faults, however, must be explicitly represented, unless the sigma (shape) factor is included in the upscaling process. A local grid-refinement approach is applied to demonstrate explicit fractures in large-scale simulation grids. This study provides guidelines on how to effectively scale up a heterogeneous fracture model and still capture the heterogeneous flow behavior.
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Freitag, Simon, Michael Drews, Wolfgang Bauer, Florian Duschl, David Misch i Harald Stollhofen. "Reconstructing post-Jurassic overburden in central Europe: new insights from mudstone compaction and thermal history analyses of the Franconian Alb, SE Germany". Solid Earth 13, nr 6 (21.06.2022): 1003–26. http://dx.doi.org/10.5194/se-13-1003-2022.
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Abstract. The Franconian Alb of SE Germany is characterized by large-scale exposures of Jurassic shallow marine limestones and dolostones, which are frequently considered to be outcrop analogues for deep geothermal reservoir rocks in the North Alpine Foreland Basin farther south. However, the burial history of the Franconian Alb Jurassic strata is not well known as they were affected by emersion, leading to extensive erosion and karstification with only remnants of the original Cretaceous and Cenozoic cover rocks preserved. To estimate the original thicknesses of the post-Jurassic overburden we investigated the petrophysical properties and the thermal history of Lower and Middle Jurassic mudstones to constrain their burial history in the Franconian Alb area. We measured mudstone porosities, densities, and maturities of organic material and collected interval velocities from seismic refraction and logging data in shallow mudstone-rich strata. Mudstone porosities and P-wave velocities vertical to bedding were then related to a normal compaction trend that was calibrated on stratigraphic equivalent units in the North Alpine Foreland Basin. Our results suggest maximum burial depths of 900–1700 m, 300–1100 m of which is attributed to Cretaceous and younger sedimentary rocks overlying the Franconian Alb Jurassic units. Compared to previous considerations this implies a more widespread distribution and increased thicknesses of up to ∼900 m for Cretaceous and up to ∼200 m for Cenozoic units in SE Germany. Maximum overburden is critical to understand mechanical and diagenetical compaction of the dolostones and limestones of the Upper Jurassic of the Franconian Alb. The results of this study therefore help to better correlate the deep geothermal reservoir properties of the Upper Jurassic from outcrop to reservoir conditions below the North Alpine Foreland Basin. Here, the Upper Jurassic geothermal reservoir can be found at depths of up to 5000 m.