Journal articles on the topic 'Poorly cemented sands'
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Hashemi, S. S., N. Melkoumian, A. Taheri, and M. Jaksa. "The failure behaviour of poorly cemented sands at a borehole wall using laboratory tests." International Journal of Rock Mechanics and Mining Sciences 77 (July 2015): 348–57. http://dx.doi.org/10.1016/j.ijrmms.2015.03.037.
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Hassane, Amadou, Chukwuemeka Ngozi Ehirim, and Tamunonengiyeofori Dagogo. "Rock physics diagnostic of Eocene Sokor-1 reservoir in Termit subbasin, Niger." Journal of Petroleum Exploration and Production Technology 11, no. 9 (August 20, 2021): 3361–71. http://dx.doi.org/10.1007/s13202-021-01259-2.
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AbstractEocene Sokor-1 reservoir is intrinsically heterogeneous and characterized by low-contrast low-resistivity log responses in parts of the Termit subbasin. Discriminating lithology and fluid properties using petrophysics alone is complicated and undermines reservoir characterization. Petrophysics and rock physics were integrated through rock physics diagnostics (RPDs) modeling for detailed description of the reservoir microstructure and quality in the subbasin. Petrophysical evaluation shows that Sokor-1 sand_5 interval has good petrophysical properties across wells and prolific in hydrocarbons. RPD analysis revealed that this sand interval could be best described by the constant cement sand model in wells_2, _3, _5 and _9 and friable sand model in well_4. The matrix structure varied mostly from clean and well-sorted unconsolidated sands as well as consolidated and cemented sandstones to deteriorating and poorly sorted shaly sands and shales/mudstones. The rock physics template built based on the constant cement sand model for representative well_2 diagnosed hydrocarbon bearing sands with low Vp/Vs and medium-to-high impedance signatures. Brine shaly sands and shales/mudstones were diagnosed with moderate Vp/Vs and medium-to-high impedance and high Vp/Vs and medium impedance, respectively. These results reveal that hydrocarbon sands and brine shaly sands cannot be distinctively discriminated by the impedance property, since they exhibit similar impedance characteristics. However, hydrocarbon sands, brine shaly sands and shales/mudstones were completely discriminated by characteristic Vp/Vs property. These results demonstrate the robust application of rock physics diagnostic modeling in quantitative reservoir characterization and may be quite useful in undrilled locations in the subbasin and fields with similar geologic settings.
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Hashemi, S. S., and N. Melkoumian. "A strain energy criterion based on grain dislodgment at borehole wall in poorly cemented sands." International Journal of Rock Mechanics and Mining Sciences 87 (September 2016): 90–103. http://dx.doi.org/10.1016/j.ijrmms.2016.05.013.
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Hashemi, S. S., A. Taheri, and N. Melkoumian. "An experimental study on the relationship between localised zones and borehole instability in poorly cemented sands." Journal of Petroleum Science and Engineering 135 (November 2015): 101–17. http://dx.doi.org/10.1016/j.petrol.2015.08.009.
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Dvorkin, Jack, and Amos Nur. "Elasticity of high‐porosity sandstones: Theory for two North Sea data sets." GEOPHYSICS 61, no. 5 (September 1996): 1363–70. http://dx.doi.org/10.1190/1.1444059.
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We have analyzed two laboratory data sets obtained on high‐porosity rock samples from the North Sea. The velocities observed are unusual in that they seem to disagree with some simple models based on porosity. On the other hand, the rocks are unusually poorly‐cemented (for laboratory studies, at least), and we investigate the likelihood that this is the cause of the disagreement. One set of rocks, from the Oseberg Field, is made of slightly cemented quartz sands. We find that we can model their dry‐rock velocities using a cementation theory where the grains mechanically interact through cement at the grain boundaries. This model does not allow for pressure dependence. The other set of rocks, from the Troll Field, is almost completely uncemented. The grains are held together by the applied confining pressure. In this case, a lower bound for the velocities can be found by using the Hertz‐Mindlin contact theory (interaction of uncemented spheres) to predict velocities at a critical porosity, combined with the modified Hashin‐Strikman lower bound for other porosities. This model, which allows for pressure‐dependence, also predicts fairly large Poisson’s ratios for saturated rocks, such as those observed in the measurements. The usefulness of these theories may be in estimating the nature of cement in rocks from measurements such as sonic logs. The theories could help indicate sand strength in poorly consolidated formations and predict the likelihood of sand production. Both theoretical methods have analytical expressions and are ready for practical use.
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Aubrecht, Roman, Tomáš Lánczos, Branislav Šmida, Charles Brewer-Carias, Federico Mayoral, Jan Schlögl, Marek Audy, Lukáš Vlček, Lubomirq Kováčik, and Miloš Gregor. "Venezuelan sandstone caves: a new view on their genesis, hydrogeology and speleothems." Geologia Croatica 61, no. 2-3 (December 25, 2008): 345–62. http://dx.doi.org/10.4154/gc.2008.27.
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Caves in arenites of the Roraima Group in Venezuela have been explored on the Chimantá and Roraima plateaus (tepuis). Geological and geomorphological research showed that the most feasible method of caves genesis was the winnowing and erosion of unlithified or poorly lithified arenites. The unlithified arenitic beds were isolated by well-cemented overlying and underlying rocks. There is a sharp contrast between these well-lithified rocks and the loose sands which form the poorly lithified to unlithified beds. They are only penetrated by strongly lithified pillars which were cemented by vertical finger flow of the diagenetic fluids from the overlying beds. Such finger flow is only typical for loose sands and soils where there is a sharp difference in hydraulic conductivity. The pillars exhibit no signs of further dissolution. The caves form when the flowing water accesses the poorly lithified beds through clefts/crevices. Collapse of several superimposed winnowed-horizons can create huge subterranean spaces. Futher upward propagation of the collapses can lead to large collapse zones which are commonly observed on the tepuis. Dissolution is also present but it probably plays neither a trigger role, nor a volumetrically important role in the cave-forming processes. The strongest dissolution/reprecipitation agent is condensed atmospheric moisture which is most likely the main agent contributing to growth of siliceous speleothems. As such, it can be active only after, but not before the cave is created. Siliceous speleothems are mostly microbialites except for some normal stalactites, cobweb stalactites and flowstones which are formed inorganically. They consist of two main types: 1. fine-laminated columnar stromatolite formed by silicified filamentous microbes (either heterotrophic filamentous bacteria or cyanobacteria) and 2. a porous peloidal stromatolite formed by Nostoc-type cyanobacteria. The initial stages of encrusted shrubs and mats of microbes were observed, too, but the surrounding arenitic substrate was intact. This is strong evidence for the microbial mediation of silica precipitation.
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Pedchenko, Larysa, Nazar Pedchenko, Jerzy Kicki, and Mykhailo Pedchenko. "Improvement of the bitumen extraction technology from bituminous sand deposits." E3S Web of Conferences 201 (2020): 01004. http://dx.doi.org/10.1051/e3sconf/202020101004.
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Today considerable experience in the development of tar sands is accumulated. However, well-known mining technologies do not cover the entire depth range of natural bitumen deposits. In addition, there are significant energy-intensive technologies and negative environmental impacts. In view of this, the purpose of this work is to improve the method of extracting natural bitumen in site for a deposit interval of 75 – 200 m and to substantiate the basic technological scheme of this method. The proposed method of extracting bitumen from poorly cemented reservoirs in the depth range of 50 – 400 m provides: creation of artificial mine working; the transfer of the rock into the water mixture composition under the action of high pressure jets of a heated mixture of water, a hydrocarbon solvent and a flotation agent; separation from the rock and concentration of bitumen in the production as a result of its heating, dissolution and flotation; selection of depleted bitum slurry from the mine working by gas lift method. The proposed method of extracting bitumen is the transfer of the rock at the site of its occurrence to the suspension condition on the excavation created by the hydraulic production method, separation and concentration of bitumen by dissolving it with a heated hydrocarbon solvent and a flotation agent (hydrocarbon reagents), and extraction in the composition of depleted rock slurry to the surface by the gas lift method. As the preliminary calculations show, the proposed method will allow the efficient extraction of bitumen and highly viscous oil from weakly cemented reservoirs in the depth range of 50 – 400 m. Also, the proposed technology creates the preconditions for the development of oil sands at a depth of 75 – 200 m since there is currently no effective technology for the interval. In addition, it can significantly reduce energy costs, environmental pollution and greenhouse gas emissions.
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Ross, Cynthia M., Edgar Rangel-German, Louis M. Castanier, Philip S. Hara, and Anthony R. Kovscek. "A Laboratory Investigation of Temperature-Induced Sand Consolidation." SPE Journal 11, no. 02 (June 1, 2006): 206–15. http://dx.doi.org/10.2118/92398-pa.
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Summary Current gravel-packed, slotted-liner completion techniques for wells in unconsolidated and weakly consolidated sandstone are relatively expensive and result in greatly reduced operational flexibility. On the other hand, empirical field evidence (Wilmington, California) demonstrates that sand grains surrounding the wellbore are cemented and consolidated following injection of high-pressure (1,600-psi) steam. Effective sand control results without adverse changes to formation permeability and producibility. Here, sand consolidation mechanisms are exposed by duplicating, in the laboratory, the governing geochemical processes. Sandpacks contain typical per-volume concentrations of concrete resulting from perforating a cased and cemented well. The evolution of sandpack pore and grain struture is determined using scanning electron microscope imaging and compositional analyses. Results show that hot alkaline water injected at rates comparable to field rates indeed results in grain-cementing precipitates. Casing cement plays a crucial role in that it is the source of calcium silicates appearing in various pore-lining precipitates. Conditions for effective sand consolidation are not necessarily formation-specific, and the process can be altered to improve cost-effectiveness, flexibility, and longevity of the completion technique. Introduction In poorly consolidated and unconsolidated sandstone reservoirs, solids are sometimes carried from the formation to the wellbore as oil and water flow toward producers. It is referred to as "sand production." This term is usually detrimental and should be avoided. Operational problems result, including extra wear of the pumping units, shorter pipe lifetime, frequent workovers, loss of well productivity, and waste-disposal issues. Several remedies are available to the engineer. They include production-rate reduction (Penberthy and Shaughnessy 1992), physical barriers (Penberthy and Shaughnessy 1992), in-situ consolidation (Prats and Hamby 1965; Davies et al. 1983; Davies et al. 1997; Davies et al. 2003), and hybrid methods (Penberthy and Shaughnessy 1992; Kruger 1986). No sand-control method is, as of yet, generally applicable. We use laboratory experiments to develop a mechanistic understanding of a novel hot alkaline/steam sand-consolidation technique. This technique has proved effective empirically (Davies et al. 1997). The mechanisms of mineral and grain dissolution, precipitation, and consolidation using Wilmington (Los Angeles basin, California) field cores and quartz sandpacks are described. Field sands are drawn from the productive, heavy-oil intervals (T and D sands) of the Tar II-A zone (Hara 2003). The tools employed are core-scale and beaker-scale experiments, scanning electron microscopy (SEM), and elemental analyses. Additionally, tubing-tail samples recovered from the field are reexamined in light of the new laboratory results. Before proceeding to the experimental details and results, a brief review of the hot alkaline/steam sand-consolidation process is given. This background is foundational, because it underpins the experimental program and interpretation of results. The experimental objectives, apparatus, and procedures follow. Results, discussion, and implications finish the paper.
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Williams, B. P. J., E. K. Wild, and R. J. Suttill. "PARAGLACIAL AEOLIANITES: POTENTIAL NEW HYDROCARBON RESERVOIRS, GIDGEALPA GROUP, SOUTHERN COOPER BASIN." APPEA Journal 25, no. 1 (1985): 291. http://dx.doi.org/10.1071/aj84026.
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Facies analysis of core from the Gidgealpa Group has led to the first recognition of sandstones of aeolian origin in the Cooper Basin. The aeolian suite was recognised in core from the Merrimelia Formation penetrated by wells within the Merrimelia field.The Merrimelia 5 aeolianites occur in core between 8603 and 8659 ft drill depth. These were correlated to similar facies in core from Merrimelia 1 between 9649 and 9674 ft drill depth, where other lithotypes of the suite were identified.Gamma ray-sonic log response over cored aeolianite intervals can be correlated to Merrimelia 13, where similar aeolian sediments are interpreted for an uncored interval of Merrimelia Formation.The overall glacigenic nature of the Merrimelia Formation is well documented but this discovery records the first aeolian suite in the Gidgealpa Group and may also document the first subsurface example of cold-climate aeolianites.The aeolianites are porous, poorly cemented, coarse and fine grained sandstones dominated by parallel lamination. Sharp, planar truncation surfaces divide the suite into units composed mainly of translatent wind ripple lamination with minor amounts of sandflow bedding. Primary depositional dip (post-compaction) varies between 0° and 25° suggesting preservation of dune lee-slope strata. Local deformation of avalanche foresets is also visible in the core.The gamma ray-sonic logs of the thick (1190 ft (363 m)) Merrimelia Formation in Merrimelia 5 indicate thick (760 ft (232 m)) porous sandstones. These originate from distal aeolian and distal sandy braidplain environments. In core from Merrimelia 1, aeolianites are interbedded with proximal outwash fan conglomerates. Also gamma ray-sonic logs of the interval indicate thinning of the aeolianite sands. These two observations indicate a nearby depositional edge to the aeolianites.A low interval transit time on sonic logs is characteristic of the porous aeolianite sand. This response produces an identifiable change in seismic reflections where the sands are developed, which allows mapping of the sand distribution from seismic data.A 6 to 8-km wide band of aeolianite sand facies trending southeast — northwest has been mapped. This porous aeolianite sand facies is interpreted to pass laterally into outwash fan, braidplain and interdune deposits.Potential hydrocarbon traps may occur at the top of the aeolianites, or within them beneath intraformational seals formed by muddy interdune facies. The recognition of an aeolian suite at Merrimelia indicates the potential for similar facies development elsewhere in the southern Cooper Basin. Locally these could form important reservoirs beneath the level of existing production.
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Loro, Richard, Robin Hill, Mark Jackson, and Tony Slate. "Technologies that have transformed the Exmouth into Australia." APPEA Journal 55, no. 1 (2015): 233. http://dx.doi.org/10.1071/aj14018.
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The oil and gas fields of the Exmouth Sub-basin, offshore WA, have presented a number of significant challenges to their exploitation since the first discoveries of heavy oil and lean gas were made in the late 1980s and early 1990s. Presently, some 20 oil and gas fields have been discovered in a variety of Late Jurassic to Cretaceous clastic reservoirs from slope turbidites to deltaic sands. Discovered oils are typically heavily biodegraded with densities ranging from 14–23° API and moderate viscosity. Seismic imaging is challenging across some areas due to pervasive multiples and gas escape features, while in other areas resolution is excellent. Most reservoirs are poorly cemented to unconsolidated and thus require sand control. Modest oil columns, most with gas caps, and variable permeability, present challenges for both maximising oil recovery and minimising the influx of water and gas. Oil-water emulsions also present difficulties for both maximising oil rate and metering production. To date, more than 300 MMbbls have been produced from five developments (Enfield, Stybarrow, Vincent, Van Gogh and Pyrenees), and in 2013 the Macedon gasfield began production. This peer-reviewed paper focuses on the variety of technologies—geoscience, reservoir, drilling and production—that have underpinned the development of these challenging fields and in doing so, transformed the Exmouth into Australia’s premier oil producing basin.
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Alsgaard, Per C., Vince L. Felt, Henrik Vosgerau, and Finn Surlyk. "The Jurassic of Kuhn Ø, North-East Greenland." Geological Survey of Denmark and Greenland (GEUS) Bulletin 1 (October 28, 2003): 865–92. http://dx.doi.org/10.34194/geusb.v1.4691.
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The Middle–Upper Jurassic succession of Kuhn Ø, North-East Greenland accumulated in a major half-graben and is an excellent analogue for the subsurface of the mid-Norwegian shelf. On Kuhn Ø, peneplaned crystalline basement was incised by a drainage system during a major base-level lowstand, probably in late Early or early Middle Jurassic times. It was filled with fluvial conglomerates of the newly defined Middle Jurassic Bastians Dal Formation during subsequent base-level rise. As sea level continued to rise, precursor-peat of the coals of the Muslingebjerg Formation formed in swamps which covered the conglomerates and filled the remaining space of the incised valley system. The valley and interfluve areas were flooded in Late Bathonian – Callovian times and tidally-dominated, shallow marine sandstones of the Pelion Formation were deposited on top of the valley fill and over the adjacent basement peneplain. These sandstones are overlain by the newly defined shallow marine Oxfordian Payer Dal Formation which is subdivided into a lower unit and an upper unit, separated by a major drowning surface. The Payer Dal Formation sands were flooded in the Late Jurassic and organic-rich, offshore mudstones of the Bernbjerg Formation were deposited. The Jurassic succession of Kuhn Ø can thus be subdivided into large-scale sedimentary units separated by major drowning surfaces. They are of regional extent, and in combination with biostratigraphic and 87Sr/86Sr isotope data they allow the correlation of the sedimentary units on Kuhn Ø with more offshore deposits to the south in Wollaston Forland and more landwards successions to the north in Hochstetter Forland. Petrographically, the trough cross-bedded sandstones of the Pelion Formation and the lower unit of the Payer Dal Formation include both calcite-cemented and poorly cemented quartz sandstones. The calcite cement was derived from dissolution of abundant calcareous fossils and forms concretionary horizons. The upper unit of the Payer Dal Formation mainly consists of weaklycemented quartz sandstones with porosities around 30%. The sandstones of the Pelion and Payer Dal Formations on Kuhn Ø are petrographically very similar to Jurassic sandstones from the mid- Norwegian shelf and the Barents Sea with regard to original mineralogical composition, sorting and grain size. The Bernbjerg Formation mudstones are comparable to the Upper Jurassic source rock of the mid-Norwegian shelf and the Barents Sea, but have lower hydrogen index (HI) values due to terrigenous input in a relatively proximal setting. Coals of the Muslingebjerg Formation have significant source rock potential with measured HI values up to 700, kerogen types II–III and total organic carbon (TOC) values above 50%.
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Fadhil, Roaa M., and Haifaa A. Ali. "Effect of Soaking and Non-soaking Condition on Shear Strength Parameters of Sandy Soil Treated with Additives." Civil Engineering Journal 5, no. 5 (May 21, 2019): 1147–61. http://dx.doi.org/10.28991/cej-2019-03091319.
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The present paper aims to improve shear strength parameters: cohesion (c), and angle of internal friction (∅) for sandy soil treated by additives before and after soaking. The samples of sandy soil were obtained from Karbala city and then classified as poorly graded sand (SP) with relative density Dr (30%) according to the system of (USCS). The experiment has three stages. In the first stage ,the soil was treated with three different percentages of cement (3 ,5 and 7%) of dry weight for the soil with three different percentages of water content (2, 4 and 8%) in each above percentage of cement, while the second stage includes (2%) of lime from soil weight mixed with each different percentage of cement . In the third stage, (50%) of polymer of cement weight was mixed with each different percentage of cement. An analysis of behavior sandy soils treated by additives was carried out with the Direct Shear Tests. All the samples were cured (3) days before and after soaking. The results of the experiment showed that increase in shear strength parameters of sandy soil; especially the angle of internal friction with the rate value (16.6 %) of cement only, (21.88 %) of cement with lime , (20.3%) of cement with the polymer before soaked condition. After soaking condition, it was increased with the rate value (14.3%) with cement only, (23.57%) of cement with lime, and (15.38%) of cement with the polymer as compared with soil in the natural state.
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Edeh, Joseph E., Adrian O. Eberemu, and Onah Agnes. "Lateritic Soil Stabilization of Reclaimed Asphalt Pavement as Flexible Highway Pavement Materials." Advanced Materials Research 367 (October 2011): 3–11. http://dx.doi.org/10.4028/www.scientific.net/amr.367.3.
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This paper presents the results of the laboratory evaluation of the characteristics of lateritic soil stabilized reclaimed asphalt pavements (RAP), using 0 – 2% cement, subjected to British Standard Light (BSL) compactive effort to determine their index, compaction and california bearing ratio (CBR) results. The result of the laboratory tests show that the properties of RAP improved when stabilized with lateritic soil, using up to 2% cement. The particle size distribution improved from poorly graded sandy GRAVELLY material for 100% lateritic soil and very sandy GRAVELLY material, to the gradation described as well graded very sandy GRAVELLY material for lateritic soil stabilized RAP, using up to 2% cement. The CBR results obtained from the study show that using the Nigerian General Specifications, 180% CBR value criterion, the maximum CBR of 55% (soaked) for the mix proportion; 40% Laterite + 58% RAP + 2% Cement for A-2-7(2) soil prescribed by the latter is not adequate for stabilization of base coarse. However, judging by the 24-hour strength gain from 17.9 (unsoaked) to 55% (soaked) CBR values, the material can be used as subgrade and subbase materials.
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SILVA, GIVANILDO ALVES DA, DANILO DE LIMA CAMÊLO, MARCELO METRI CORRÊA, VALDOMIRO SEVERINO DE SOUZA JÚNIOR, MATEUS ROSAS RIBEIRO FILHO, and JOSÉ COELHO DE ARAÚJO FILHO. "PEDOGENESIS ON COASTAL TABLELANDS AREA WITH LOW RANGE ALTIMETRY IN PARAÍBA STATE." Revista Caatinga 32, no. 2 (June 2019): 458–71. http://dx.doi.org/10.1590/1983-21252019v32n219rc.
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ABSTRACT Small variations of relief may change drainage and runoff and hence promote the formation of sandy surface horizons and hardened subsurface horizons (fragipans and/or duripans) in Coastal Tablelands soils. This study aimed to investigate the pedogenesis on Coastal Tablelands area with low range altimetry in Paraíba state; secondly, we also sought to contribute to the improvement of the Brazilian Soil Classification System (BSCS). Four soil profiles ware described and collected to be submitted to routine physical and chemical analysis, determination of Fe, Al and Si extracted by sulfuric acid digestion, sodium citrate-bicarbonate-dithionite and acid ammonium oxalate, sodium pyrophosphate, and mineralogical analysis in the sand and clay fractions by X-ray diffractometry. Optical density of the oxalate extract (ODOE) was also determined; the results were statistically evaluated using the R software. Microrelief variations conditioning differentiated water flows, along with the sandy texture of the surface horizons (A and E) and the lower coarse sand/fine sand ratio in the subsurface horizon, seem to promote clay accumulation in depth in the Spodosols developed on Coastal Tablelands environments. For this soils, the argilluvic (argissólico) character at the subgroup level of the BSCS should be incorporated. In addition, Al amorphous mineral phases and/or poorly crystalline play an important role in the formation of strongly cemented horizons (duripans) of the Spodosols, as also reported by other authors. Finally, the ODOE showed to be an efficient indicator of soils under podzolization process, being possible its use as a taxonomic criterion for classification of Spodosols by the BSCS.
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Okoyeh, Elizabeth I., Anthony E. Akpan, B. C. E. Egboka, and H. I. Okeke. "An Assessment of the Influences of Surface and Subsurface Water Level Dynamics in the Development of Gullies in Anambra State, Southeastern Nigeria." Earth Interactions 18, no. 4 (January 1, 2014): 1–24. http://dx.doi.org/10.1175/2012ei000488.1.
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Abstract Gully erosion–induced problems have been challenging the people and government of Anambra State in southeastern Nigeria for a long time. In spite of the numerous geoscientific and engineering studies so far conducted in the area, the underlying causes of these problems still remain poorly understood. In an attempt to contribute to the understanding of the underlying processes responsible for the persistent gully erosion problems in Anambra State, an integrated study utilizing hydrological, geomorphological, and geophysical data was undertaken. Results of the analyses show that bulk density, pH, and organic matter content of the soil range from 1610 to 1740 kg m−3, 5.10 to 5.30, and 0.32% to 0.46%, respectively. Particle size analyses results show that the soils are dominated by coarse sand materials (50%–68%). Variations in the Atterberg limit parameters (liquid limit, plastic limit, and plasticity index) also point to the dominance of coarse materials in the shallow subsurface. Vertical electrical sounding results capture the shallow surface as being dominated by resistive sandy materials that are underlain by lowly resistive clayey materials. Thus, the area is dominated by porous, friable, and poorly cemented coarse materials that are located on a long and steeply sloping terrain of the tectonically elevated Awka–Orlu cuesta. Both overland and subsurface flow processes are responsible for the gully erosion problems confronting the area. Human activities (e.g., deforestation, uncontrolled urbanization, and absence of requisite legislation to protect the environment) and the high elevation of the Awka–Orlu cuesta have aggravated the severity of the problems. An aggressive reforestation program particularly with native trees, promulgation of necessary legislation to protect the environment, and setting up and empowering an enforcement agency should be vigorously pursued. Also, necessary enlightenment campaigns on best agricultural practices that can reduce surface runoff in soil and water conservation may also be helpful in changing the mindset of people.
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Hersi, Osman Salad, and Abdulrahman AL-Harthy. "Lithofacies Attributes of a Transgressive Carbonate System : The Middle Eocence Seeb Formation, Al Khoud Area, Muscat, Oman." Sultan Qaboos University Journal for Science [SQUJS] 15 (December 1, 2010): 41. http://dx.doi.org/10.24200/squjs.vol15iss0pp41-54.
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The Seeb Formation (Middle Eocene) is an about 600 m thick transgressive carbonate succession deposited in the Batina and Muscat coastal region of Oman. The formation consists of five informal, but distinct units, and their stacking architecture suggests a deepening-upward, shallow marine depositional setting. Unit I is characterized by cross-bedded, sandy, bioclastic packstones to grainstones deposited in a high energy beach-to-intertidal environment. Unit II consists of indistinctly bedded, nodular, bioclastic (mainly larger foraminifera) packstones and wackestones deposited in a logoonal lagoonal environment. Unit III is defined by medium to thickly bedded, bioclastic packestones to grainstones and subordinate, laterally confined conglomerates. Prominent sedimentary structures in Unit III include hummocky and swaly cross-stratificiation, erosional surfaces, dewatering-induced deformations and laterally amalgamating beds. This unit represents sub-tidal sand shoals deposited in a storm-dominated shelf (between the fair-weather wave-base and storm-base). Unit IV is extensively burrowed, nodular, bioclastic wackestone to rudstone which is similar to Unit II in many aspects. Unit IV was deposited on the basinward side of the Unit III sand shoals below the reach of the storm-generated waves and currents. The uppermost Unit V is characterized by poorly-cemented bioclastic (large foraminiferal) rudstones with clay and silt-size quartz matrix. Bioclasts are generally intact with no apparent reworking. Deposition of Unit V is also envisaged as a low-energy, outershelf environment.
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Saul, Matthew, and David Lumley. "The combined effects of pressure and cementation on 4D seismic data." GEOPHYSICS 80, no. 2 (March 1, 2015): WA135—WA148. http://dx.doi.org/10.1190/geo2014-0226.1.
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Time-lapse seismology has proven to be a useful method for monitoring reservoir fluid flow, identifying unproduced hydrocarbons and injected fluids, and improving overall reservoir management decisions. The large magnitudes of observed time-lapse seismic anomalies associated with strong pore pressure increases are sometimes not explainable by velocity-pressure relationships determined by fitting elastic theory to core data. This can lead to difficulties in interpreting time-lapse seismic data in terms of physically realizable changes in reservoir properties during injection. It is commonly assumed that certain geologic properties remain constant during fluid production/injection, including rock porosity and grain cementation. We have developed a new nonelastic method based on rock physics diagnostics to describe the pressure sensitivity of rock properties that includes changes in the grain contact cement, and we applied the method to a 4D seismic data example from offshore Australia. We found that water injection at high pore pressure may mechanically weaken the poorly consolidated reservoir sands in a nonelastic manner, allowing us to explain observed 4D seismic signals that are larger than can be predicted by elastic theory fits to the core data. A comparison of our new model with the observed 4D seismic response around a large water injector suggested a significant mechanical weakening of the reservoir rock, consistent with a decrease in the effective grain contact cement from 2.5% at the time/pressure of the preinjection baseline survey, to 0.75% at the time/pressure of the monitor survey. This approach may enable more accurate interpretations and future predictions of the 4D signal for subsequent monitor surveys and improve 4D feasibility and interpretation studies in other reservoirs with geomechanically similar rocks.
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Bosikov, I. I., A. I. Mazko, and A. V. Mayer. "A comprehensive evaluation of the productive formation collector of the Kanevskoye field." Oil and Gas Studies, no. 3 (July 15, 2021): 25–36. http://dx.doi.org/10.31660/0445-0108-2021-3-25-36.
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At the present stage, the development of the oil and gas industry of the Russian Federation is impossible without replenishing the resource base, and therefore an urgent task is to conduct research, prospecting and evaluating petroleum potential in undiscovered areas of fields. The aim of the study is to conduct a comprehensive assessment of the reservoir of the productive formation of the Kanevskoye field. We have carried out mineralogical and petrographic studies, laboratory studies to assess the effective porosity of the core sample by the saturation method, particle size analysis, X-ray diffraction analysis. Our studies have shown that the considered initial sands under consideration, which formed the reservoir rocks of the productive horizon of the Kanevskoye field, were formed by coastal or beach type marine sediments. This is confirmed by the poorly rounded shape of the grains and the presence of glauconite in the rocks. The studied core sample is a fine-grained glauconite-feldspar-quartz sandstone with an admixture of aleurite fraction, with semi-rounded grains, pelitic cement, basal and porous-basal, silt-psammitic structure. The total porosity is 14.3 %. A comprehensive assessment of the reservoir of the productive formation of the Kanevskoye field has been carried out. The reservoir is productive. Therefore, it is necessary to make a project for conducting geological exploration.
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Nohl, Theresa, Jannick Wetterich, Nicholas Fobbe, and Axel Munnecke. "Lithological dependence of aragonite preservation in monospecific gastropod deposits of the Miocene Mainz Basin: Implications for the (dia-)genesis of limestone–marl alternations." Journal of Sedimentary Research 90, no. 11 (November 30, 2020): 1500–1509. http://dx.doi.org/10.2110/jsr.2020.057.
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ABSTRACTThe origin of limestone–marl alternations (LMA) and their diagenesis is still lively debated. The most disputed question is whether original variations in sediment input control the differentiation of the precursor sediment into limestone and marl, or if a LMA can form without compositional differences in the precursor sediment. The Miocene brackish-water deposits (Rüssingen Formation) from the Mainz–Weisenau quarry in central Germany offer the opportunity to tackle this question. They are developed as a monospecific alternation of planar beds of moderately and poorly lithified sands of aragonitic Hydrobia snails, corresponding to “limestones” and “marls” in LMA, respectively. XRD analyses and the monospecific composition reveal only minor to no changes in sedimentary input and allow comparison of the preservation of Hydrobia in both lithologies. The differential preservation of the aragonitic fossils in lithified and less lithified layers is documented in thin-sections. CaCO3 contents are high throughout the measured section. However, XRD analyses revealed high amounts of aragonite and low amounts of calcite in less lithified beds, and the opposite in lithified beds in which calcite is the main mineral phase. Mg-calcite is abundant in both lithologies. Although the less lithified beds have experienced significant loss of aragonite by dissolution, they still mainly contain aragonite since the precursor sediment contained only aragonitic shells and Mg-calcite crusts. The relative amount of aragonite is higher than in the more lithified beds because the lithified beds imported the dissolved aragonite, which precipitated as calcite cements. This shifted the aragonite–calcite ratio to higher values in the less lithified beds than in the more lithified beds, although it is counterintuitive at first sight. This is supported by thin-section analyses and point counting, revealing moderate to good preservation of Hydrobia or their replacement by calcite spar in lithified beds, but intense dissolution of aragonite in less lithified beds. The aragonite–calcite ratio and the differential preservation of Hydrobia fit the model of differential diagenesis in “classical” LMAs, which assumes early diagenetic aragonite dissolution in marls and reprecipitation as calcite cement in limestones. It is concluded that the studied succession—although an endmember of LMA—was differentiated into lithified and unlithified beds by incomplete differential diagenesis while minor primary differences are not reflected in the change in lithology. The results suggest that the differentiation of a homogeneous precursor sediment into a LMA is possible and caution should be exercised using lithological change or proxies which are potentially altered by CaCO3 redistribution for cyclostratigraphic analyses.
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Ramseyer, Karl, Joachim E. Amthor, Christoph Spötl, Jos M. J. Terken, Albert Matter, Marietta Vroon-ten Hove, and Jean R. F. Borgomano. "Impact of basin evolution, depositional environment, pore water evolution and diagenesis on reservoir-quality of Lower Paleozoic Haima Supergroup sandstones, Sultanate of Oman." GeoArabia 9, no. 4 (October 1, 2004): 107–38. http://dx.doi.org/10.2113/geoarabia0904107.
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ABSTRACT Sandstones of the Early Paleozoic Miqrat Formation and Barik Sandstone Member (Haima Supergroup) are the most prolific gas/condensate containing units in the northern part of the Interior Oman Sedimentary Basin (IOSB). The reservoir-quality of these sandstones, buried to depths exceeding 5 km, is critically related to the depositional environment, burial-related diagenetic reactions, the timing of liquid hydrocarbon charge and the replacement of liquid hydrocarbon by gas/condensate. The depositional environment of the sandstones controls the net-sand distribution which results in poorer reservoir properties northwards parallel to the axis of the Ghaba Salt Basin. The sandy delta deposits of the Barik Sandstone Member have a complex diagenetic history, with early dolomite cementation, followed by compaction, chlorite formation, hydrocarbon charge, quartz and anhydrite precipitation and the formation of pore-filling and pore-lining bitumen. In the Miqrat Formation sandstone, which is comprised of inland sabkha deposits, similar authigenic minerals occur, but with higher abundances of dolomite and anhydrite, and less quartz cement. The deduced pore water evolution from deposition to recent, in both the Miqrat Formation and the Barik Sandstone Member, reflects an early addition of saline continental waters and hydrocarbon-burial related mineral reactions with the likely influx of lower-saline waters during the obduction of the Oman Mountains. Four structural provinces are recognized in the IOSB based on regional differences in the subsidence/uplift history: the Eastern Flank, the Ghaba and Fahud Salt Basins and the Mabrouk-Makarem High. In the Fahud Salt Basin, biodegradation of an early oil charge during Late Paleozoic uplift resulted in reservoir-quality degradation by bitumen clogging of the pore space. On the Eastern Flank and the Mabrouk-Makarem High, however, the early oil bypassed the area. In contrast, post-Carboniferous liquid hydrocarbons were trapped in the Mabrouk-Makarem High, whereas on the Eastern Flank surface water infiltration and loss of hydrocarbons or biodegradation to pore occluding bitumen occurred. In the Ghaba Salt Basin, post-Carboniferous hydrocarbon charge induced a redox reaction to form porosity/permeability preserving chlorite in the reservoirs. The liquid hydrocarbons were replaced since the obduction of the Oman Mountains by gas/condensate which prevented the deep parts (>5,000 m) of the Ghaba Salt Basin from pore occluding pyrobitumen and thus deterioration of the reservoir quality.
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Wilkinson, M., R. S. Haszeldine, and A. E. Fallick. "Jurassic and Cretaceous clays of the northern and central North Sea hydrocarbon reservoirs reviewed." Clay Minerals 41, no. 1 (March 2006): 151–86. http://dx.doi.org/10.1180/0009855064110197.
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AbstractThe principal clays of the northern and central North Sea are illite (sometimes with interlayered smectite) and kaolin. Chlorite is only locally important. Although it has been proposed that kaolin within North Sea sandstones is detrital in origin, the majority of workers have concluded that it is authigenic, largely the product of feldspar alteration. Kaolin is found within a wide range of sedimentary settings (and within shales) apparently defying the notion that kaolin is an indicator of meteoric water deposition. Within sandstones, the earliest authigenic kaolin has a vermiform morphology, the distribution of which is controlled by the availability of detrital mica to act as a nucleus, and the composition of the post-depositional porewaters. This vermiform kaolin formed in meteoric water, the presence of which is easily accounted for below sub-aerial exposure surfaces in non-marine formations, and below unconformities over marine units. In fully marine sands, and even marine shale units, kaolin still occurs. It has therefore been suggested that even these locations have been flushed with meteoric water.Early vermiform kaolin recrystallizes to a more blocky morphology as burial proceeds, at least in the Brent Group. Blocky kaolin has been reported as growing before, synchronously with, and after the formation of quartz overgrowths, though oxygen isotope studies support low-temperature growth, pre-quartz. Blocky kaolin may form during meteoric flushing associated with lower Cretaceous uplift and erosion, though it is found in fault blocks that are thought to have remained below sea level. Here, the kaolin may form in stagnant meteoric water, relics of the post-depositional porewater. It has also been proposed that the blocky kaolin grew in ascending basinal waters charged with carboxylic acids and CO2, though this hypothesis is not supported by stable oxygen isotope data. Some of the blocky kaolin is dickite, the stable polymorph above ∼100°C.Fibrous illite occurs almost ubiquitously within the clastic sediments of the North Sea. An early pore-lining phase has been interpreted as both infiltrated clastic clay, and as an early diagenetic phase. Early clays may have been quite smectite-rich illites, or even discrete smectites. Later, fibrous illite is undoubtedly neoformed, and can degrade reservoir quality significantly. Both within sandstones and shales, there is an apparent increase in the K content deeper than 4 km of burial, which could be due to dilution of the early smectite-rich phase by new growth illite, or to the progressive illitization of existing I-S. Much of the ‘illite’ that has been dated by the K-Ar method may therefore actually be I-S.The factors that control the formation of fibrous illite are only poorly known, though temperature must play a role. Illite growth has been proposed for almost the entire range of diagenetic temperatures (e.g. 15–20°C, Brent Group; 35–40°C, Oxfordian Sand, Inner Moray Firth; 50–90°C, Brae formation; 100–110°C, Brent Group; 130–140°C, Haltenbanken). It seems unlikely that there is a threshold temperature below which illite growth is impossible (or too slow to be significant), though this is a recurring hypothesis in the literature. Instead, illite growth seems to be an event, commonly triggered by oil emplacement or another change in the physiochemical conditions within the sandstone, such as an episode of overpressure release. Hence fibrous illite can grow at any temperature encountered during diagenesis.Although there is an extensive dataset of K-Ar ages of authigenic illites from the Jurassic of the North Sea, there is no consensus as to whether the data are meaningful, or whether the purified illite samples prepared for analysis are so contaminated with detrital phases as to render the age data meaningless. At present it is unclear about how to resolve this problem, though there is some indication that chemical micro-analysis could help. It is a common belief that illite ages record the timing of oil charge, and so can be used to calibrate basin models.Grain-coating Fe-rich chlorite cements can preserve exceptional porosity during burial. They are found in marginal marine sandstones, formed during diagenesis from precursor Fe-rich clays such as berthierine or verdine.
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Konstantinou, Charalampos, Yuze Wang, Giovanna Biscontin, and Kenichi Soga. "The role of bacterial urease activity on the uniformity of carbonate precipitation profiles of bio-treated coarse sand specimens." Scientific Reports 11, no. 1 (March 17, 2021). http://dx.doi.org/10.1038/s41598-021-85712-6.
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AbstractProtocols for microbially induced carbonate precipitation (MICP) have been extensively studied in the literature to optimise the process with regard to the amount of injected chemicals, the ratio of urea to calcium chloride, the method of injection and injection intervals, and the population of the bacteria, usually using fine- to medium-grained poorly graded sands. This study assesses the effect of varying urease activities, which have not been studied systematically, and population densities of the bacteria on the uniformity of cementation in very coarse sands (considered poor candidates for treatment). A procedure for producing bacteria with the desired urease activities was developed and qPCR tests were conducted to measure the counts of the RNA of the Ure-C genes. Sand biocementaton experiments followed, showing that slower rates of MICP reactions promote more effective and uniform cementation. Lowering urease activity, in particular, results in progressively more uniformly cemented samples and it is proven to be effective enough when its value is less than 10 mmol/L/h. The work presented highlights the importance of urease activity in controlling the quality and quantity of calcium carbonate cements.
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Gago, Paula A., Charalampos Konstantinou, Giovanna Biscontin, and Peter King. "A Numerical Characterisation of Unconfined Strength of Weakly Consolidated Granular Packs and Its Effect on Fluid-Driven Fracture Behaviour." Rock Mechanics and Rock Engineering, May 12, 2022. http://dx.doi.org/10.1007/s00603-022-02885-w.
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AbstractSoft or weakly consolidated sand refers to porous materials composed of particles (or grains) weakly held together to form a solid but that can be easily broken when subjected to stress. These materials do not behave as conventional brittle, linear elastic materials and the transition between these two regimes cannot usually be described using poro-elastic models. Furthermore, conventional geotechnical sampling techniques often result in the destruction of the cementation and recovery of sufficient intact core is, therefore, difficult. This paper studies a numerical model that allows us to introduce weak consolidation in granular packs. The model, based on the LIGGGHTS open source project, simply adds an attractive contribution to particles in contact. This simple model allows us to reproduce key elements of the behaviour of the stress observed in compacted sands and clay, as well as in poorly consolidated sandstones. The paper finishes by inspecting the effect of different consolidation levels in fluid-driven fracture behaviour. Numerical results are compared qualitatively against experimental results on bio-cemented sandstones.
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"Improving the Shear Strength of the Soil by using Jute Fabric." International Journal of Recent Technology and Engineering 8, no. 4 (November 30, 2019): 6627–30. http://dx.doi.org/10.35940/ijrte.d8846.118419.
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Bearing capacity of the soil is based on the shear strength of the soil. By improving the shear strength, bearing capacity of soil increases. Various additives such as lime, fly ash, cement, bitumen, tar etc. and easily available on-site materials such as sands, mining waste, natural stone waste etc were using to improve the shear strength of the soil. The main aim of this project is to improve the shear strength of the soil by adding jute fabric in various proportions. Jute fabric is mainly produced from a plant species called Corchorus olitorius. Soil samples were collected from Mangalapuram, Trivandrum and the identification tests such as specific gravity, liquid limit, plastic limit and sieve analysis of soil were done based on IS2720 recommended procedures. As per IS1498 – 1970 the soil is classified as poorly graded sands (SP). Jute fabric is added to the soil on 3%, 6% and 9% of weight of soil sample. Standard proctor test is conducted as per IS 2720 (part VII) to determine the optimum moisture content value (OMC). Optimum moisture content value of the soil sample is 10%. The shear strength of the soil is determined by direct shear strength test, which is conducted on both treated and untreated soil sample. From the result it is concluded that by adding 6% of jute fabric the shear strength of the soil reaches its maximum value, further addition of jute fabric reduces the shear strength of soil. Hence it is recommended to use 6% of jute fabric in sub-grade soils for pavements to improve the shear strength.
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Onyelowe, Kennedy C., Ahmed M. Ebid, Jair de Jesús Arrieta Baldovino, and Michael E. Onyia. "Hydraulic conductivity predictive model of RHA-ameliorated laterite for solving landfill liner leachate, soil and water contamination and carbon emission problems." International Journal of Low-Carbon Technologies, July 25, 2022. http://dx.doi.org/10.1093/ijlct/ctac077.
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Abstract The environment is seriously being affected by the leachate release at the unconstructed and badly constructed waste containment or landfill facilities around the globe. The worst hit is the developing world where there is little or totally no waste management system and facilities to receive waste released into the atmosphere. This research work is focused on the leachate drain into the soil and the underground water from landfills, which toxicifies both the soil and the water. Also, the construction of the liner or barrier with cement poses serious threat to the environment due to oxides of carbon release and this research also took this into account by replacing the utilization of cement with rice husk ash (RHA), which has proven to have the potentials of replacing cement as a supplementary binder. Laboratory tests were conducted to determine the hydraulic conductivity (K) of lateritic soil ameliorated with different dosages of RHA. Other hydromechanical properties of the treated blend were studied and multiple data was generated for the artificial neural network (ANN) back-propagation (-BP), genetic algorithm (−GA), & gradual reducing gradient (−GRG), genetic prohgramming (GP) & evolutionary polynomial regression (EPR) prediction exercises. Results show that the lateritic soil (LS) was a poorly graded A-2 sandy silt soil, which was subjected to three different compaction energies with the minimum of the British standard light (BSL) and derived k of 6.95E-10, 50.75E-10 and 32.33E-10 for BSL, west African standard (WAS) and British standard heavy (BSH) respectively. The RHA addition improved the studied properties of the ameliorated LS. Out of the five models, the ANN-GRG outclassed others with a performance of 99% with minimal error compared to the rest. Potentially, this research has shown that RHA with a PCM of 81.47% can replace cement in the construction of ecofriendly and more efficient landfills and waste containemnt barriers to save the soil and the underground water as well as the environment from leachate contamination and carbon emissions.