Tesi sul tema "Limestone reservoir"

A test site for CO2 geological storage is situated in Hontomín (Burgos, northern Spain) with a reservoir rock that is mainly composed of limestone (80-85%) and sandstone (15-20%). The reservoir rock is a deep saline aquifer that is covered by a very low permeability formation which acts as a cap rock. During and after CO2 injection, since the resident groundwater contains sulfate, the resulting CO2-rich acid solution gives rise to the dissolution of carbonate minerals (calcite and dolomite) and secondary sulfate-rich mineral precipitation (gypsum or anhydrite) may occur. These reactions that may imply changes in the porosity, permeability and pore structure of the repository could vary the CO2 storage capacity and injectivity of the reservoir rock. Therefore, better knowledge about the overall process of gypsum precipitation at the expense of carbonate mineral dissolution in CO2-rich solutions and its implications for the hydrodynamic properties of the reservoir rocks is necessary. A first aim of this thesis is to better understand these coupled reactions by assessing the effect that P, pCO2, T, mineralogy, acidity and solution saturation state exert on these reactions. To this end, experiments using columns filled with crushed limestone or dolostone are conducted under different P-pCO2 conditions (atmospheric:1-10-3.5 bar; subcritical: 10-10 bar; and supercritical: 150-34 bar), T (25, 40 and 60 °C) and input solution compositions (gypsum-undersaturated and gypsum-equilibrated solutions). The CrunchFlow and PhreeqC (v.3) numerical codes are used to perform 1D reactive transport simulations of the experiments to evaluate mineral reaction rates in the system and quantify the porosity variation along the column. Within the range of P-pCO2 and T of this study only gypsum precipitation takes place and this only occurs when the injected solution is equilibrated with gypsum. Under the P-pCO2-T conditions, the volume of precipitated gypsum is smaller than the volume of dissolved carbonate minerals, yielding always an increase in porosity (¿¿ up to ¿ 4%). A decrease in T favors limestone dissolution regardless of pCO2 owing to increasing undersaturation with decreasing temperature. However, gypsum precipitation is favored at high T and under atmospheric pCO2 conditions but not at high T and under 10 bar of pCO2 conditions. The increase in limestone dissolution with pCO2 is directly attributed to pH, which is more acidic at higher pCO2. A decrease in T favors limestone dissolution regardless of pCO2 owing to increasing undersaturation with decreasing temperature. However, gypsum precipitation is favored at high T and under atmospheric pCO2 conditions but not at high T and under 10 bar of pCO2 conditions. The increase in limestone dissolution with pCO2 is directly attributed to pH, which is more acidic at higher pCO2. Limestone dissolution induces late gypsum precipitation (long induction time) in contrast to dolostone dissolution, which promotes rapid gypsum precipitation. Moreover, owing to the slow kinetics of dolomite dissolution with respect to that of calcite, both the volume of dissolved mineral and the increase in porosity are larger in the limestone experiments than in the dolostone ones under all pCO2 conditions (10-3.5 and 10 bar). Limestone dissolution induces late gypsum precipitation (long induction time) in contrast to dolostone dissolution, which promotes rapid gypsum precipitation. Moreover, owing to the slow kinetics of dolomite dissolution with respect to that of calcite, both the volume of dissolved mineral and the increase in porosity are larger in the limestone experiments than in the dolostone ones under all pCO2 conditions (10-3.5 and 10 bar).
Una planta pilot per a l'emmagatzematge geològic de CO2 es troba a Hontomín (Burgos). El reservori és un aqüífer salí profund, format principalment per roca calcària (80-85%) i gres (15-20%), que està situat entre dues capes de molt baixa permeabilitat que actuen com a roques segell. La dissolució de CO2 a l'aigua del reservori provocarà una disminució del pH i, en conseqüència, la dissolució dels carbonats presents en el reservori. Tenint en compte que l'aigua resident és rica en sulfat, és possible la precipitació de minerals secundaris (guix o anhidrita). Aquestes reaccions poden provocar canvis en la porositat, la permeabilitat i l'estructura de por del reservori que, a la vegada, poden afectar la seva injectivitat i capacitat d'emmagatzematge. Per tant, cal aprofundir en el coneixement sobre els processos acoblats de precipitació de guix i dissolució de carbonats (calcita i dolomita) en solucions riques en CO2 dissolt i les seves implicacions en les propietats hidrodinàmiques de la roca reservori. Un primer objectiu d'aquesta tesi és poder comprendre millor aquestes reaccions acoblades mitjançant l'avaluació de l'efecte que exerceixen la pressió P, la pressió parcial de CO2 pCO2, la temperatura T, la mineralogia, l'acidesa i l'estat de saturació de la solució sobre aquestes reaccions. Amb aquest objectiu, s'han realitzat una sèrie d'experiments utilitzant columnes plenes de roca calcària o dolomia triturada sota diferents condicions de P-pCO2 (atmosfèrica: 1-10-3.5 bar; subcrítica: 10-10 bar, i supercrítica: 150-34 bar), T (25, 40 i 60 ° C) i composició de la solució d'entrada (solucions subsaturades o equilibrades amb guix). Els codis numèrics CrunchFlow i PhreeqC (v.3) s'han utilitzat per realitzar simulacions de transport reactiu dels experiments en columna amb l'objectiu d'avaluar les velocitats de reacció en el sistema i quantificar la variació de la porositat al llarg de la columna. En les condicions de P-pCO2-T estudiades, la precipitació de guix únicament té lloc quan la solució injectada està en equilibri amb guix. A més, el volum de guix precipitat és menor que el volum de carbonat dissolt, originant sempre un augment de porositat. Una disminució en la T afavoreix la dissolució de la calcària independentment de la pCO2 degut a l'augment de la subsaturació. No obstant, la precipitació de guix està afavorida a alta T per condicions atmosfèriques, originant-se l¿efecte contrari per condicions subcrítiques. L'augment de la pCO2 comporta un augment en la dissolució de calcària, fet que és directament atribuït a l'efecte del pH, que és més àcid a major pCO2. La dissolució de calcària comporta un retard en la precipitació de guix (llarg temps d'inducció), al contrari del que passa amb la dissolució de dolomia que promou una ràpida precipitació de guix. A més, a causa de la lenta cinètica de dissolució de la dolomita amb respecte a la de la calcita, el volum de mineral dissolt i l'augment de porositat són majors en els experiments amb calcària sota totes les condicions de pCO2 estudiades. La dissolució de calcària comporta un retard en la precipitació de guix (llarg temps d'inducció), al contrari del que passa amb la dissolució de dolomia que promou una ràpida precipitació de guix. A més, a causa de la lenta cinètica de dissolució de la dolomita amb respecte a la de la calcita, el volum de mineral dissolt i l'augment de porositat són majors en els experiments amb calcària sota totes les condicions de pCO2 estudiades. La dissolució del carbonat es produeix al llarg de tota la columna quan la pCO2 és alta (10 and 34 bar) i, en canvi, es localitza a l'entrada de la columna sota condicions atmosfèriques. Aquesta diferència és deguda a la capacitat tampó de l'àcid carbònic, ja que manté el pH al voltant de 5 i la solució subsaturada pel que fa a la calcita i a la dolomita al llarg de la columna

Master of Science
Department of Geology
Matthew Totten
Jackson County, Kansas is situated on the west side of the Forest City Basin, location of the first oil discovery west of the Mississippi River (KGS), Production in the area is predominately from the Viola Limestone, and a noticeable trend of oil fields has developed where the basin meets the Nemaha Anticline. Exploration has been sluggish, because of the lack of an exploration model. Production rates have varied widely from well to well, even when they are structurally equivalent. The goal of this study was to determine the factors controlling reservoir quality in the Ordovician-aged Viola Limestone so that a better exploration model could be developed. A two township area was studied to examine relationships between subsurface variations and production rates. In the absence of an available core through the Viola, drill cuttings were thin-sectioned and examined under a petrographic microscope to see the finer details of porosity, porosity type and dolomite crystal-size that are not visible under a binocular microscope. Production appears to be controlled by a combination of structural position and dolomite crystal size, which was controlled by secondary diagenesis in the freshwater-marine phreatic mixing zone. The best wells exhibited a Viola Limestone made up of 100% very coarsely crystalline, euhedral dolomite crystals. These wells occur on the east and southeast sides of present day anticlines, which I have interpreted to be paleo-highs that have been tilted to the east-southeast.

Lower Triassic strata in the Wellington Flat and Tully cores reflect a lateral transition from shallow water strata (Wellington Flats core) to strata that indicate deposition on a relatively more distal, storm-dominated ramp (Tully core). The Sinbad Member, along with the upper part of the underlying Black Dragon Member and the lower part of the overlying Torrey Member (Moenkopi Formation), are composed of ten carbonate, siliciclastic and mixed carbonate/siliciclastic facies deposited on a west-facing ramp/shelf that reached maximum flooding during Smithian time. Individual beds and facies display a large degree of lateral homogeneity and regional persistence in the study area. The Wellington Flats core contains the three units characteristic of outcropping Sinbad Limestone: a basal skeletal unit, a middle peloidal unit, and an upper, oolitic dolomite unit. The more offshore Tully core is composed of skeletal grainstone, with fewer shallow-water carbonate and siliciclastic deposits. Discontinuity surfaces (hardgrounds, firmgrounds, and change surfaces) are common and indicate that sedimentation was punctuated by short-lived hiatuses accompanied by cementation, scour, and/or encrustation of the sediment-water interface. The Black Dragon, Sinbad, and lower Torrey Members represent at least one 3rd-order depositional sequence bounded below by the Tr-1 unconformity and above by lowstand deposits in the middle Torrey Member. Amalgamated fluvial channels in the middle of the Black Dragon Member may represent an additional 3rd-order sequence boundary that separates a Greisbachian sequence (lower Black Dragon Member) from the Smithian sequence (upper Black Dragon through lower Torrey members), but this is unsubstantiated by biostratigraphic data at present. Diagenesis is strongly controlled by facies. Diagenetic elements include marine fibrous calcite cements, micritized grains, compaction, dissolution and neomorphism of aragonite grains, meteoric cements, pressure dissolution, and dolomitization. The paragenetic sequence progresses from marine to meteoric to burial. Marine and meteoric cements occlude much of the depositional porosity, which ranges from 0 to 10 % in the sample interval. The best reservoir qualities in core (1.0 md) occur in grainstones and quartz-siltstones. Although its relative thinness precludes it from being a major producer, the Sinbad Limestone Member of the Moenkopi Formation bears potential for modest future oil production.

The Lower Triassic Sinbad Limestone Member of the Moenkopi Formation has produced minor amounts of oil in the Grassy Trail Creek field near Green River, Utah and is present below much of central Utah including the recently discovered Covenant field. Superb outcrops of this thin (15 m), mixed carbonate-silicilastic unit in the San Rafael Swell permit detailed analysis of its vertical and lateral reservoir heterogeneity. Vertically, the Sinbad Limestone comprises three facies associations: (A) a basal storm-dominated, well-circulated skeletal-oolitic-peloidal limestone association, (B) a storm-dominated, poorly-circulated hummocky cross-stratified siliciclastic/peloidal association, and (C) a capping peritidal cross-bedded oolitic dolograinstone association. Eleven microfacies are present in 14 measured sections within the Sinbad Limestone. Lateral variation is most pronounced in the upper part of the basal limestone where storm-deposited beds pinch out over a lateral distance of one kilometer. Otherwise, individual beds and microfacies display a large degree of lateral homogeneity and regional persistence. Diagenesis is strongly controlled by microfacies. Diagenetic elements include marine fibrous calcite cements, micritized grains, compaction, dissolution and neomorphism of aragonite grains, meteoric cements, pressure dissolution, and dolomitization. The paragenetic sequence progresses from marine to meteoric to burial. Marine and meteoric cements occlude much of the depositional porosity. Hydrocarbon-lined interparticle and separate vug (largely molds) pores (1-5%) characterize the skeletal-oolitic limestones with permeability ranging from 0-100 md. Low permeability/porosity characterizes the middle silicilastic unit. The best reservoir qualities (permeability 400 md) occur in portions of the dolomitized oolitic grainstones that form the upper 2 to 3 m of the Sinbad Limestone. Fracture analysis of the studied area indicates a strong NW-SE trend. Fracture spacing is associated with lithology. Fracturing of limestone possibly displays a higher dependence upon bed thickness and microfacies type. The degree of dolomitization controls and increases fracture spacing while siltstones display more closely spaced fractures. The basal limestone unit is an oil storage unit, medial siltstones are flow baffles/barriers, and the dolostone caprock is an oil flow unit. If good connectivity through fractures can be obtained between the dolostone and limestone units, the Sinbad Limestone has potential to serve as a reservoir. This study will not only aid in future Sinbad exploration, but will serve as a model for parasequence-scale intervals in thicker mixed carbonate-siliciclastic successions.

Master of Science
Department of Geology
Abdelmoneam Raef
Seismic reservoir characterization and prospect evaluation based 3D seismic attributes analysis in Kansas has been successful in contributing to the tasks of building static and dynamic reservoir models and in identifying commercial hydrocarbon prospects. In some areas, reservoir heterogeneities introduce challenges, resulting in some wells with poor economics. Analysis of seismic attributes gives insight into hydrocarbon presence, fluid movement (in time lapse mode), porosity, and other factors used in evaluating reservoir potential. This study evaluates a producing lease using seismic attributes analysis of an area covered by a 2010 3D seismic survey in the Morrison Northeast field and Morrison field of Clark County, KS. The target horizon is the Viola Limestone, which continues to produce from seven of twelve wells completed within the survey area. In order to understand reservoir heterogeneities, hydrocarbon entrapment settings and the implications for future development plans, a seismic attributes extraction and analysis, guided with geophysical well-logs, was conducted with emphasis on instantaneous attributes and amplitude anomalies. Investigations into tuning effects were conducted in light of amplitude anomalies to gain insight into what seismic results led to the completion of the twelve wells in the area drilled based on the seismic survey results. Further analysis was conducted to determine if the unsuccessful wells completed could have been avoided. Finally the study attempts to present a set of 3D seismic attributes associated with the successful wells, which will assist in placing new wells in other locations within the two fields, as well as promote a consistent understanding of entrapment controls in this field.

SummaryThe displacement of oil from reservoir rock pore spaces is a function of many interacting variables, amongst which the reservoir wetting state has been shown to be one of the important affected by the rock lithology, oil chemistry and brine salinity. A finding from previous research says that the injection brine into oil saturated core plug increased oil recovery. Based on this the objective of this master thesis is to investigate the effect of brine concentration on flow properties in two types of carbonate rocks for enhanced oil recovery (EOR) through imbibition and water flooding processes.The methodology used to evaluate the effect of brine concentration (BC) and chemical composition (CC) for oil recovery consisted on two stages. The first stage covers the literature review regarding the effect of brine concentration and chemical composition, including carbonates (chalk and limestone) characteristics. The second stage is related to the laboratory experiment which was performed using n-Decane oil, six (6) brines with different concentrations and chemical composition and the six (6) core plugs where four (4) “chalks” from Ekofisk (Norway) and the other two (2) “limestones” from Iranian field. The experiment was carried out in the laboratory of Institute of Petroleum and Technology (IPT), the materials, chemicals products, apparatus and equipments, methodology and procedures were provided by the IPT laboratory.To carry out the laboratory experiments, initially the two cores from Iranian were cleaned before being used. Different properties of brines, cores and oil were measured using different methods and procedures; and results were computed. Next, each core was saturated with one type of brine and after that flooded by n-Decane oil for establishment of initial water saturation and determination of volume of oil produced by drainage process at room temperature conditions at one bar. After that, all cores were aging about 15 days at room temperature condition. Finally, each core was flooded using brine by imbibition process at room temperature conditions.Results achieved were computed and discussed based on the literature review and compared with “A salinity (AS) Ekofisk core reference case” and similar studies. From this study was observed that the matrix block has a high porosity. The average porosity was about 40.24% of the volumes of large pores. The average absolute permeability was about 3.73 mD which is low because the microporous dominate the pore network. The average brine density (ρ) was about1.026 g/cm3 and pH was about 7.25. The initial water saturation varies between 14.58 to 28.50% and residual oil saturation among 22.49 to 62%. The sleeve pressure in the cylinder was kept from 15 to 28 bar. During waterfloodig was observed that the breakthrough pressure drop and time to increases when the oil recovery increase.The highest original oil in place (OOIP) was achieved in the low salinity (LS) core which was about 68.46% and the lowest was recorded in the C salinity (CS) core which was around 26.71%. The reason of the high and the low recovery is related with the effect of brine concentration and chemical composition of Sodium, Calcium, Magnesium and Sulphate, added in the solution. The main driving mechanism for low salinity waterflooding is believed to be multi component ionic exchange made possible by the expansion of electrical double layer. The permeability and porosity of the cores can be pointed as other factor. In general, it was showen that there is an increase in oil recovery as the salinity decreases.

Gripen Oil & Gas have extended their prospecting license on Gotland to the north end of the island to search for potential hydrocarbon reservoirs. Earlier prospecting has shown that limestone mound structures from Ordovicium have high potential as hydrocarbon reservoirs due to their antiformal shape and the petrophysical properties of the limestone.This study focuses on the petrophysical properties of the intramound lithofacies of the Ordovician mound structures. Analyses are made to determine the density, porosity and ultrasonic velocity of ten drill core samples (both in dry and water-filled state) from different places on Gotland and these factors are compared to see how they affect one another. Seismic reflection data gathered by OPAB (provided by SGU) is also used to locate potential mound structures in northern Gotland.The results show a clear connection between the density and porosity. Increasing porosities also decreases the ultrasonic velocities of the rocks. The saturated samples show higher velocities for the compressional waves than in the dry samples, but the shear wave velocity is similar in both dry and saturated rocks. Acoustic impedance is used to link the petrophysical analysis to the geophysical data by explaining why one reflector can be seen more clearly than others in a seismic section. Using the seismic sections, five possible mounds are found on northern Gotland. Good correlations are found in the petrophysical analyses, but the porosity of the rock does not seem to be the deciding factor in choosing a reservoir. There is no association between a rock’s measured porosity and its potential extraction volume, clearly shown by the low porosity measured in the Risungs drill cores compared to how much volume of oil that has been extracted. Instead, one should look closer at the seismic sections to find mounds with a high degree of fracturing. None of the mounds seen in the seismic sections show any apparent fracturing, and more seismic surveys should be made before deciding where to drill.

Master of Science
Department of Geology
Abdelmoneam Raef
Advancements, applications, and success of time-lapse (4D) seismic monitoring of carbonate reservoirs is limited by these systems’ inherent heterogeneity and low compressibility relative to siliciclastic systems. To contribute to the advancement of 4D seismic monitoring in carbonates, an investigation of amplitude envelope across frequency sub-bands was conducted on a high-resolution 4D seismic data set acquired in fine temporal intervals between a baseline and eight monitor surveys to track CO₂-EOR from 2003-2005 in the Hall-Gurney Field, Kansas. The shallow (approximately 900 m) Plattsburg ‘C Zone’ target reservoir is an oomoldic limestone within the Lansing-Kansas City (LKC) supergroup – deposited as a sequence of high-frequency, stacked cyclothems. The LKC reservoir fluctuates around thin-bed thickness within the well pattern region and is susceptible to amplitude tuning effects, in which CO₂ replacement of initial reservoir fluid generates a complex tuning phenomena with reduction and brightening of amplitude at reservoir thickness above and below thin-bed thickness, respectively. A thorough analysis of horizon snapping criteria and parameters was conducted to understand the sensitivity of these autonomous operations and produce a robust horizon tracking workflow to extend the Baseline Survey horizon data to subsequent Monitor Surveys. This 4D seismic horizon tracking workflow expedited the horizon tracking process across monitor surveys, while following a quantitative, repeatable approach in tracking the LKC and maintaining geologic integrity despite low signal-to-noise ratio (SNR) data and misties between surveys. Analysis of amplitude envelope data across frequency sub-bands (30-80 Hz) following spectral decomposition identified geometric features of multiple LKC shoal bodies at the reservoir interval. In corroboration with prior geologic interpretation, shoal boundaries, zones of overlap between stacked shoals, thickness variation, and lateral changes in lithofacies were delineated in the Baseline Survey, which enhanced detail of these features’ extent beyond capacity offered from well log data. Lineaments dominated by low-frequency anomalies within regions of adjacent shoals’ boundaries suggest thicker zones of potential shoal overlap. Analysis of frequency band-to-band analysis reveals relative thickness variation. Spectral decomposition of the amplitude envelope was analyzed between the Baseline and Monitor Surveys to identify spectral and tuning changes to monitor CO₂ migration. Ambiguity of CO₂ effects on tuning phenomena was observed in zones of known CO₂ fluid replacement. A series of lineaments highlighted by amplitude brightening from the Baseline to Monitor Surveys is observed, which compete with a more spatially extensive effect of subtle amplitude dimming. These lineaments are suggestive of features below tuning thickness, such as stratigraphic structures of shoals, fractures, and/or thin shoal edges, which are highlighted by an increased apparent thickness and onset of tuning from CO₂. Detailed analysis of these 4D seismic data across frequency sub-bands provide enhanced interpretation of shoal geometry, position, and overlap; identification of lateral changes in lithofacies suggestive of barriers and conduits; insight into relative thickness variation; and the ability of CO₂ tuning ambiguity to highlight zones below tuning thickness and improve reservoir characterization. These results suggest improved efficiency of CO₂ -EOR reservoir surveillance in carbonates, with implications to ensure optimal field planning and flood performance for analogous targets.

This thesis is a multi-scale study of carbonate rocks, from the nanoscale and digital rock investigations to the imaging studies of carbonate reservoir analogues. The essential links between these extremes are the carbonate physical properties and rock-physics models, which are investigated here through the modelling of ultrasonic wave propagation in carbonate samples, focusing on elastic stress sensitivities, saturating fluids and porosity models. Validation of Gassmann fluid substitution in carbonates is also investigated using correlations between core and well log measurements.On the nanoscale, we use the nanoindentation technique in an oolitic limestone to directly measure the calcite Young modulus and derive bulk and shear moduli. We have found a large variation in the calcite bulk modulus, from 56 to 144 GPa. The high values obtained in some oolite rings were interpreted as genetically associated with biologically generated calcite (biocalcite). There are many measurements that achieve these values in brachiopod shells, but none in oolitic limestone. We associate the smaller values with microporosity, which is undetectable by our microCT or even SEM images. On the microscale we use the X-ray microCT images. From these images we can compute oolite elastic parameters using finite difference methods (FDM). In this oolite sample, calcite was segmented in two distinct phases. Nanoindentation provides the elastic parameters for each phase. The results of the modelling are compared with ultrasonic measurements on dry samples.To compute the properties of rocks on fluid-saturated samples, one needs to use fluid substitution methods, such as Gassmann’s equations. However, the applicability of Gassmann’s equations and the fluid substitution technique to carbonate rocks is still a subject of debate. Here we compare the results of fluid substitution applied to dry core measurements against sonic log data. The 36 meters of continuously sampled carbonates data, comes from a cretaceous reservoir buried at a depth of 5000 metres in the Santos Basin, offshore Brazil. Compressional and shear velocities, density and porosity were measured in 50 samples covering the entire interval. We obtain good agreement between the elastic properties obtained from core and log measurements. This shows that Gassmann’s fluid substitution is applicable to these carbonates, at least at sonic log frequencies.Carbonate microstructure is investigated using the stress dependency of shear and compressional wave velocities according to the dual porosity model of Shapiro (2003). The model assumes that the pore space contains two types of pores: stiff and compliant pores. Understanding the parameters of this model for different rocks is important for constraining stress effects in these rocks. The results for a carbonate dataset from the Santos Basin show a good correlation between compliant porosity and dry bulk modulus, total porosity and density for 29 samples of carbonates from the Santos Basin. The correlations seem to be different for different facies distribution, with different trends for mudstone facies and grainstone and rudstone facies. We also performed the same analysis using 66 samples of sandstones of diverse origins (Han et al., 1986): a good correlation appears between compliant porosity and the dry bulk modulus for all samples.If we correlate only the 7 samples from Fontainebleau sandstone, a good correlation also appears between total and compliant porosity. This analysis shows that the correlation is facies dependent also for sandstones.While Gassmann’s equations may be valid for low frequencies, they are not applicable at higher frequencies, where squirt dispersion is significant. We propose a workflow to model wave dispersion and attenuation due to the squirt flow using the geometrical parameters of the pore space derived from the stress dependency of elastic moduli on dry samples. Our analysis shows the dispersion is controlled by the squirt flow between equant pores and intermediate pores (with aspect ratios between 10-3 - 2·10-1). Such intermediate porosity is expected to close at confining pressures of between 200-2000 MPa. We also infer the magnitude of the intermediate porosity and its characteristic aspect ratio. Substituting these parameters into the squirt model, we have computed elastic moduli and velocities of the water-saturated rock and compared these predictions against laboratory measurements of these velocities.The agreement is good for a number of clean sandstones, but much worse for a broad range of shaley sandstones. Our predictions show that dispersion and attenuation caused by the squirt flow between compliant and stiff pores may occur in the seismic frequency band. Confirmation of this prediction requires laboratory measurements of elastic properties at these frequencies.The carbonate system of Telegraph Station, Shark Bay (WA), is a unique environment where coquinas, stromatolites and microbial mats are linked: an excellent analogue to carbonate pre-salt offshore Brazil. We acquired 7.5 km of GPR data and high resolution seismic data in the coquina ridges. They are composed by calcite shells deposited by cyclones, which show excellent high resolution GPR images, being a low loss dielectric medium. Three classes of coquinas were mapped: tabular layers, convex-up crest and washover fan. From the correlation of 14C dating of 50 samples and the mapped events we can estimate an average rate of one event every 13 years. From our interpretation the Holocene regression is continuous but not homogeneous. Carbonate dissolution features, faults, trends and discontinuities were mapped. Analysis of these features helps us understand reservoir porosity and permeability distribution in carbonate deposits, and can be used to constrain reservoir properties in pre-salt carbonates in Brazilian basins.

Observations of modern carbonate depositional environments and their accompanying depositional models have been used for decades in the reconstruction and interpretation of ancient carbonate depositional environments and stratigraphic successions. While these Holocene models are necessary for interpreting their more ancient counterparts, they inherently exclude important factors related to the erosion, diagenesis, and ultimate preservation of sediments and sedimentary structures that are ubiquitous in shallow marine carbonate environments. Andros Island, Bahamas is an ideal location to examine the validity of Holocene conceptual models, where geologically young (Late Pleistocene) limestones can be studied immediately adjacent to their well-documented modern equivalents. For this study, two 3D ground-penetrating radar (GPR) datasets (200 MHz and 400 MHz) were collected at a schoolyard in northwest Andros. These surveys reveal the geometries and internal characteristics of a peloidal-oolitic sand wave and tidal channel in unprecedented detail. These two prominent features are underlain by low-energy lagoonal wackestones and packstones, and are bordered laterally to the northwest by wackestones-packstones intermixed with thin sheets of peloidaloolitic grainstone. A deeper radar surface is observed at approximately 6 m depth dipping gently to the west, and is interpreted to be a karstified exposure surface delineating the base of a complete depositional sequence. Interpretation of the 3D radar volumes is enhanced and constrained by data from three cores drilled through the crest and toe of the sand wave, and through the tidal channel. This study is the first of its kind to capture the complex heterogeneity of a carbonate depositional package in three dimensions, where various depositional environments, sedimentary structures, and textures (mudstone to grainstone) have been preserved within a small volume.The results from this study suggest that the degree of vertical and lateral heterogeneity in preserved carbonate successions is often more complex than what can be observed in modern depositional environments, where sediments can generally only be observed in two dimensions, at an instant in time. Data from this study demonstrate the value of using two overlapping GPR datasets at differing resolutions to image the internal characteristics of a complete carbonate depositional package in three dimensions. From these datasets, a depositional model similar to other Holocene and Pleistocene carbonate depositional models is derived.

Le stockage géologique est aujourd'hui envisagé dans plusieurs domaines tels que le stockage de CO2 ou celui de déchets nucléaires. C'est un projet à long terme qui nécessite un protocole d'étude particulier afin de déterminer et comprendre la formation envisagée, notamment en termes de mécanismes de transports. Les formations étudiées sont fonction du type de stockage dans le sens où un stockage de gaz ou de déchet radioactifs ne vont pas requérir les mêmes besoins. Dans le cas d'un stockage de CO2, la formation hôte doit posséder de bonnes propriétés réservoirs afin de, notamment, faciliter l'injection. Pour un stockage de déchets radioactifs, la formation hôte doit retenir au maximum les éventuelles fuites de fluides contaminés, c'est pourquoi les sites de stockage envisagés sont au sein de formation très peu poreuse et très peu perméable, argilite ou granite notamment.Les travaux présentés dans cette thèse sont liés à deux projets de stockage. Le premier a pour but l'étude pétrophysique d'une formation potentiellement hôte d'un stockage de CO2 dans le Bassin Parisien, la formation carbonatée de l'Oolithe Blanche. Cette formation, composée de trois faciès principaux, présente de faibles propriétés réservoir qui sont influencées par trois paramètres microstructuraux : la nature du liant, la quantité de compaction et, enfin, la taille des pores et leur distribution.Le second projet est basé sur l'étude d'un analogue structurale au laboratoire de Meuse/Haute-Marne de l'Andra pour le stockage de déchets radioactifs. Cet analogue est situé dans l'archipel Maltais, qui présente une structure tabulaire très proche de celle observée dans la région du laboratoire de Meuse/Haute-Marne : calcaire/argile/calcaire. Notre étude a permis la mise en évidence de plusieurs périodes de mouvement de fluides oxydants, dont une traversant l'ensemble de la formation argileuse, remettant ainsi en cause ses propriétés d'imperméabilité
Geological storage is now considered as a technical solution for CO2 storage andnuclear waste management (for high-level and intermediate-level long-lived radioactivewaste). A geological storage is a long term project which implies a particular protocol in orderto better determine and to better understand the host rock, especially in terms of transportmechanisms. The geological formations studied are chosen in function of their storagecapacity because gas storage or nuclear waste storage do not need the same requirements.In case of CO2 storage, the host formation must provide good reservoir properties in order tofacilitate the injection. Here, the safety of the storage is guaranteed by traps (structural,residual, mineral) and by the presence of a cap rock. Concerning nuclear waste storage, thehost must retain at best the potential radioactive fluids and gaz leaks, and this is the reasonwhy storage sites are studied within low porous and low permeable formation, like argillite orgranite.The work presented in the PhD thesis is related to two storage projects. The first oneis focused on the petrophysical study of a potential host for CO2 storage in the Paris Basin,the “Oolithe Blanche” carbonate formation. The second project is an analogue study of thesedimentary structure explored in the Meuse/Haute-Marne laboratory. This laboratory isstudied by ANDRA to be the first nuclear waste storage in a deep geological formation inFrance. The analogue was found in maltese archipelagos, which presents almost the sametabular structure as the one observed in the Meuse/Haute-Marne laboratory:limestone/clay/limestone affected by a weak tectonique deformation.In the first part, the Oolithe Blanche Formation study allowed to determine thereservoir properties of the three principals facies of the formation. This study was realized onplugs sampled on quarries in Burgundy (France). Those facies are characterized by differentenvironmental processes and deposit energy; nonetheless, they are all located within ashoreface depositional environment. They are composed of ooids, pellets and bioclasts invarying proportions. The reservoir properties studied showed the Oolithe Blanche Formationis a microporous one. Microstructural parameters which influence reservoir properties are:the cement type (sparite or micrite), amount of compaction characterized by the cementquantity and the contact between elements and, at last, the pore size distribution withinporous elements (micro, meso, macropores).The second part of this project is focused on a more petrophysical study which aimedat characterizing the pore network influence (volume, shape in space) on acoustic velocities,6electrical conductivity and on permeability. The study is completed by the use of permeabilitypredictive models based on mercury porosimetry spectra.The maltese archipelagos study is based on observations made by Missenard et al.(in prep.) .), Rocher et al., (2008) and Missenard et al. (2009, 2011) on the Blue ClayFormation, thick clay formation (~ 100 m) and on the underlying Globigerina Limestone. Theclay formation presents an important fracture network characterized by gypsum filling and byan oxidizing zone near the fractures. A similar oxidation, in the shape of lobes andmushrooms, is observed within the Globigerina Limestone.This study is also divided in two parts. In the first one, the focus is on the study ofgypsum filling fractures. Studying this filling is directly linked with the storage topic, because,in the case of a nuclear waste storage, the absence of fractures and fluid motion is animportant condition to insure the storage security. In the case of gypsums filling, the study isbased on geochemical measurements on oxygen (δ18O), sulphur (δ34S) and strontiumisotopes (87Sr/86Sr) coupled with a fluid inclusion study, all measurements performed ongypsum crystal. Those analyses allow us to propose a downward fluids circulation modelthrought the clays. Fluids source which is at the origin of gypsum’s precipitation seems to beyounger than the hosted formation. Because of the position of the maltese islands, inMediterranean sea, one potential source is the Messinian evaporites, which Sr isotopic ratiocorresponds well to our data set.The second part of the maltese study concerns the oxidation shape observed withinthe Globigerina Limestone. The aim is to determine the processes which allowed thisoxidation. The main question is: are those structures the results of an internal heterogeneityin the rock or the sign of a stop in a fluid motion (stop of the fluid or stop of the oxidizingmechanism)? In order to answer those questions we based our interpretaion on the skeletonof the rock (mineralogy, magnetic mineralogy, microstructural study, geochemistry), on poreand porosity (porosity measurements, mercury porosimetry…), on permeability and on therock anisotropy (susceptibility of magnetic anisotropy (SMA) and acoustic velocitiesanisotropy). Some conflicting differences on the dataset exist, especially on anisotropy data,which can suppose some complex processes

Master of Science
Geology
Matthew W. Totten
The Mississippian-aged St. Louis Limestone of Western Kansas is a carbonate resource play that has been producing oil, gas, and natural gas liquids (NGL) for over 50 years. The Mississippian Limestone is made up of heterogeneous limestones with interbedded layers of porous and non-porous units, abrupt facies changes, and diagenetic alterations. These factors combine to characterize the St. Louis Limestone's internal complexity, which complicates hydrocarbon exploration. This study focuses on improving the understanding of the geometry, distribution, and continuity of depositional facies within Kearny County, Kansas. Petrophysical analysis of a suite of geophysical logs integrated with core provided the basis for establishing facies successions, determining vertical stacking patterns within a sequence stratigraphic framework, and correlating areas of high porosity with a respective facies. The following depositional facies were identified; 1) porous ooid grainstone, 2) highly-cemented ooid grainstone, 3) quartz-carbonate grainstone, 4) peloidal grainstone, 5) micritic mudstone, and the 6) skeletal wackestone/packstone. The porous ooid grainstone is the chief reservoir facies, with log-derived porosity measurements between four and eighteen percent. In areas without available core, depositional facies were predicted and modeled using a neural network analysis tool (Kipling2.xla). Values derived from the evaluated core intervals and their respective geophysical logs served as the framework for the neural network model. This study illustrates the advantages of correlating depositional facies with reservoir quality and correlating those specific facies to geophysical logs, ultimately to create a greater understanding of the reservoir quality and potential within the St. Louis Limestone of western Kansas.

In this study, I use the cross-hole method to examine the relationship between fractures in limestone reservoirs, where the presence of fractures has been determined by a priori information, and the shear-wave anisotropy of the rockmass. I process and interpret multicomponent seismic data from two producing areas: the East Fitts field Oklahoma, where a multi-azimuthal cross-hole survey is used to image the Hunton and Viola reservoir formations at depths of 3000-4000 feet; and the Iatan East Howards field, Texas, where two cross-hole azimuths are used to image the Clearfork reservoir formation at a similar depth. I apply a numerical method to measure the shear-wave splitting parameters, qS1 polarization and time delay between qS1 and qS2 arrivals, and best-fit parameters for reservoir crack strike and crack density are determined by forward modelling. The observed qS1 polarizations at three azimuths from the East Fitts site can be related to propagation through two thin layers, representing the Hunton and Viola reservoir zones, each containing distributions of micro-cracks with a best-fit strike of N35°E. The observed time delays between qS1 and qS2 arrivals can also be modelled by lower crack densities distributed throughout the layered model. Polarization measurements at one cross-hole azimuth from the Iatan site agree with a priori reservoir fracture direction of N60°E-N85°E. Results from the second azimuth fall within the expected zone of behaviour for cracks striking ±12.5° of N170°E. A measured qS1 polarization direction of N170°E from near-offset VSP data at the Iatan site also disagrees with the known reservoir fracture direction. The Iatan measurements are incompatible with hexagonal anisotropic symmetry with a horizontal axis of symmetry. No improvements in the resolution of the anisotropic parameters of fractured rocks and reservoirs was achieved by using the cross-hole method although propagation through the near-surface is avoided. Acceptable model solutions have been found for the observations, however, the problems of non-uniqueness are inherent in the forward modelling approach.

Master of Science
Department of Geology
Matthew W. Totten
The area of study for this project is the Leach Field, which is located in Jackson County, Kansas. Production in the Leach Field has historically been disappointing, with 388,787 barrels of oil being produced since the field’s discovery in 1963 (KGS, 2015). Production of the field has been highly variable, with only 20,568 barrels of oil being produced in the last 20 years. Economic and other concerns that have impacted production and production rates of the field include: low oil prices soon after its discovery, numerous changes of ownership, and lack of significant production infrastructure in the area. Stroke of Luck Energy & Exploration, LLC. has recently purchased the majority of the leases and wells in the Leach Field, and is reestablishing the field as a productive oil field. Plans include: washing down several plugged and abandoned wells, and drill new wells to increase production in the field. The goal of this study was to determine the major geologic factors controlling reservoir quality in the Hunton and Viola Limestone Formations in the Leach Field, so that a future exploration model can be developed to help increase and stabilize the field's overall production. This model was created by applying several testing methods including: well logging analysis, microscope analysis, and subsurface mapping. Based on these results it was determined that the quality of the reservoir rocks is controlled by the degree of dolomitizaiton in both formations. Reservoir quality is as important as structure in determining well productivity in the Leach Field.

SEDIMENTOLOGY AND STRATIGRAPHY OF TÜ
RBEYANI MARL SEQUENCES AND iNPiRi LIMESTONES (LATE BARREMIAN - ALBIAN): IMPLICATIONS FOR POSSIBLE SOURCE AND RESERVOIR ROCKS (NW TURKEY) Anar Nabiyev M.Sc., Department of Geological Engineering Supervisor: Assist. Prof. Dr. i. Ö
mer Yilmaz April 2007, 105 pages Sedimentology, cyclostratigraphy and sequence stratigraphy of the Tü
rbeyani Marls (Albian) and the inpiri Limestone (Upper Barremian-Albian) members of Ulus Formation (incigez, Bartin, Amasra) were interpreted in this study. In the Tü
rbeyani Marls total of five different facies were defined. Marl and limestone facies are the most abundant in the succession. The depositional environment of the succession was defined as an outer shelf area. Within the pelagic marls 39 smaller order and 9 higher order cycles were recognized. These cycles correspond to the parasequences and parasequence sets of sequence stratigraphy, respectively. In the measured section only one type-3 sequence boundary was identified. In the inpiri Limestones great variety of limestone facies are represented. Bioclastic, peloidal, intraclastic wackestone-packstone-grainstone facies are the most abundant. Moreover, occurrence of lime mudstone, fenestral limestone, ooid packstone-grainstone, and sandstone facies are present as well. In the measured section of the inpiri Limestones 25 fifth order and 6 fourth order cycles were defined. These cycles correspond to the parasequence sets and systems tracts of the sequence stratigraphy, respectively. Total of three transgressive and three highstand systems tract were defined. Only one type 2 sequence boundary was identified in the measured section, the rest of them are interrupted by covers. This study revealed that the Tü
rbeyani Marls and the inpiri Limestones are not economically valuable as petroleum source and reservoir rocks, respectively. The total organic carbon (TOC) values of marl facies of the Tü
rbeyani marls are very low, and the pore spaces observed in the inpiri Limestone are cement filled making it unsuitable reservoir rock. Keywords: sedimentology, cyclostratigraphy, sequence stratigraphy, Tü
rbeyani Marls, inpiri Limestones, Albian, Upper Barremian, Amasra, Bartin.

La prise de conscience de la communauté internationale et la convergence des données scientifiques autour du réchauffement climatique confirment l'urgence de déployer des technologies pour réduire les émissions de gaz à effet de serre. Cependant, ces gaz peuvent s'échapper des réservoirs géologiques profonds et migrer vers les aquifères sus-jacents et la surface. Il est donc nécessaire de mettre en place des systèmes de surveillance du stockage géologique du CO2 pour détecter ces éventuelles fuites et évaluer leur importance et leur impact sur la qualité de l'eau des aquifères. En cas de fuite dans le contexte de réservoirs utilisés pour le stockage du CO2, le CH4 résiduel du réservoir de stockage sera probablement entraîné avec le CO2. Cependant, peu d’études ont abordé les implications de la présence de CH4, et aucune son potentiel en tant que gaz précurseur permettant la surveillance des fuites d’un stockage géologique. L'étude des processus physico-chimiques et des impacts des fuites de CO2 associées au CH4 en cas de fuite sur un aquifère carbonaté proche de la surface nécessite une meilleure caractérisation des processus multi-échelles tels que la dissolution à l'échelle du réseau poreux ou le transport des panaches à l'échelle macroscopique. Les méthodes expérimentales et de modélisation utilisées individuellement donnent des réponses à des questions sur des processus particuliers, mais ces méthodes ont des limites si elles sont utilisées individuellement. Par conséquent, une approche hybride et multi-échelle est nécessaire. Le site expérimental de Saint-Émilion, avec huit forages déjà en place au niveau de l'aquifère de l'Oligocène supérieur, et les expériences passées portant sur les fuites sur les aquifères, offre une excellente opportunité pour une étude multi-échelle expérimentale et de modélisation. Dans cette thèse, l'impact des fuites a été étudié à l'échelle de la carotte en laboratoire, plus spécifiquement sur la compréhension des facteurs contrôlant les processus de dissolution tels que les faciès sédimentaires carbonatés, la vitesse de la nappe, la salinité et de la concentration de CO2. À l'échelle macroscopique, une expérience d'injection d'eau riche en CO2-CH4 a été menée sur le site de Saint-Émilion pour mieux comprendre le comportement physico-chimique du CO2 et du CH4 dans l'aquifère carbonaté. Enfin, les résultats expérimentaux ont été utilisés pour la simulation 3D du transport réactif lors d'un événement de fuite, avec le but de vérifier les résultats expérimentaux et d'étudier les processus de fuite à l'échelle macroscopique dans diverses conditions. Des relations ont été établies entre la cinétique de dissolution des carbonates, la concentration de CO2, le débit d'injection et la salinité. Des liens entre la cinétique de dissolution et l'évolution de la porosité, de la perméabilité, des paramètres électriques et le type de faciès sédimentaire ont été déterminés. L'expérience d'injection sur le site de Saint-Émilion a révélé que : i) certains paramètres physico-chimiques permettent de distinguer la fuite des gaz du signal physico-chimique naturel de l’aquifère ; ii) le déplacement du panache de CO2 est retardé par rapport au déplacement du panache de CH4 ; et iii) la corrélation entre la conductivité électrique et la concentration en CO2 permet de détecter et de suivre une fuite de CO2. De plus, l'approche par modélisation numérique du transport réactif nous a permis d'étudier comment les paramètres de la fuite peuvent modifier la propagation des panaches de CO2 et de CH4 en trois dimensions dans les milieux poreux. La modélisation a également permis d’établir l'influence des interactions de surface sur le transport du CO2 et du CH4. Ces résultats influent directement sur l'élaboration de stratégies efficaces de surveillance et d'atténuation des fuites de CO2 et de CH4 dans les sites de stockage géologique
The awareness of the international community and the convergence of scientific data around global warming confirm the urgency of deploying technologies to reduce greenhouse gas emissions. However, these gases can escape from deep geological storage and migrate to the overlying aquifers and the surface. It is therefore necessary to set up monitoring systems for geological CO2 storage to detect these possible leaks and assess their importance and impact on the water quality of the aquifers. In the event of a leak in the context of depleted reservoirs used for CO2 storage, the residual CH4 from the storage reservoir will likely be entrained with CO2. However, few studies have addressed the implications of the presence of CH4, and none have studied its potential as a precursor gas for monitoring leaks from geological storage. Studying the physicochemical processes and impacts of CO2 leakage associated with CH4 in the event of a leak on a near-surface carbonate aquifer requires better characterization of multi-scale processes such as dissolution at the scale of the porous network or the transport of plumes at the macroscopic scale. Experimental and modeling methods used individually give responses to questions on particular processes, but these methods have limitations if used individually. Therefore, a hybrid, multi-scale approach is necessary. The experimental site of Saint Émilion, with eight wells already in place at the level of the Upper Oligocene aquifer, and past experiments on leakage in this aquifer, provides an excellent opportunity for a comprehensive multi-scale experimental and modeling study. In this thesis, the impact of leakage was studied at the scale of the core in the laboratory, more specifically on the comprehension of factors that control the dissolution processes such as carbonate sedimentary facies, groundwater velocity, salinity, and CO2 concentration. At the macroscopic scale, a CO2-CH4-rich water injection experiment was conducted at the Saint-Émilion site to understand better the physicochemical behavior of CO2 and CH4 in the carbonate aquifer. Finally, the experimental results were used for the 3D simulation of the reactive transport during a leakage event, with the aim of verifying the experimental results and studying the leakage processes at the macroscopic scale under various conditions. Relationships between the dissolution kinetics for each CO2 concentration, injection rate, and salinity were established. Links between dissolution kinetics, evolution of porosity, permeability, electrical parameters, and the type of sedimentary facies were determined. The injection experiment at the Saint-Émilion site revealed that : (i) some physicochemical parameters are able to distinguish the gas leakage signal from the natural physicochemical signal of the aquifer; ii) CO2 plume displacement is retarded relative to the CH4 plume displacement; and iii) the correlation between electrical conductivity and CO2 concentration enables detection and track a CO2 leakage. Moreover, the reactive transport modeling approach has allowed us to study how the parameters of the leak can modify the propagation of CO2 and CH4 plumes in three dimensions in the porous media. Modeling also enabled to establish the influence of surface interactions on CO2 and CH4 transport. These findings directly affect the development of effective monitoring and mitigation strategies for CO2 and CH4 leaks in geological storage sites

Carbon geo sequestration (CGS) is considered one of the promising approaches to reducing anthropogenic greenhouse gas emissions into the environment. Furthermore, Underground Hydrogen Storage (UHS) has been also identified as a viable solution to effectively stored hydrogen in geological formations. The underground storage of hydrogen (UHS) project has the potential to overcome the supply and demand imbalance by a subsequent withdrawal during periods of renewable energy shortage. Depleted petroleum reservoirs and deep saline aquifers are considered favorable candidates for long-term H2 and CO2 storage. H2 and CO2 become trapped in the reservoir by various physical and chemical mechanisms, and these mechanisms mainly include residual trapping and structural trapping, dissolution, and mineralization trapping. The wettability of rock minerals for storage gas in the presence of brine is a significant physicochemical factor that largely affects the trapping mechanism. The reservoir formations naturally contain small concentrations of water-soluble organic components in particular humic acid (HA). These organic components in formations also assist the growth of various natural organotrophic microorganisms. While the earlier investigations suggest the impact of organic matter and microorganisms on wetting behaviour for enhanced oil recovery applications, we here argue that these organic matter and microorganisms have a significant effect on the CO2 and H2 wettability of the subsurface formations as well. Therefore, we prepared organic acid and bacteria-treated surfaces, and the effects of these treated surfaces on the H2 and CO2 wettability of subsurface reservoirs were evaluated via advancing and receding contact angle measurements, streaming zeta potential, and NMR techniques, at various organic acid concentrations, high pressures (up to 25 MPa), elevated temperatures (up to 333 K) and brine salinity (up to 0.3 M NaCl), that simulate the subsurface reservoir conditions. The surface characterizations were examined by high-resolution scanning electron microscopy (SEM) and atomic force (AFM) microscopy imaging while other characterization tools (e.g. TOC, EDX, and FTIR) were also implemented to gain a broader insight into the observed wetting behaviour. Our results demonstrate that water-soluble organic acid concentration significantly changes rock wettability from water-wet (0-50o) towards CO2-wet (90-110o). Furthermore, a strong correlation exists between surface adsorption of organic acid and streaming potential coefficient, where the amount of residual water saturation decreases in organic acid aged cores – suggesting the presence of organic acid changes wettability towards CO2 wet in pores. The low organic content WA basalt was initially water-wet but with increasing pressure, it was also converted into a completely CO2-wet at pressures exceeding 15 MPa and 323 K. The results of bacteria-treated quartz surfaces suggest that (1) bacterial growth is prominent on the quartz surfaces with organic matter and, (2) the originally hydrophilic surfaces tend to become less hydrophilic while the hydrophobic surfaces turn less hydrophobic in the presence of microorganisms. The results of this investigation provide a fundamental understanding of H2 and CO2 wettability alteration in the subsurface microbial environment along with organic acid, thus, having implications for de-risk the large-scale carbon geo-sequestration (CGS) and underground hydrogen storage (UHS) projects.

El análisis de estructuras paleokársticas ha atraído, en los últimos años, el interés de numerosos investigadores a la información que aportan a la geología aplicada y la paleogeomorfología. Estudios recientes se han centrado en la aplicación de técnicas de exploración del subsuelo debido a la escasez de afloramientos. En la presente Memoria se analizan íntegramente las formas de hundimiento pretéritas que afloran discontinuamente con gran detalle, en los acantilados de las costas meridional (plataforma de Llucmajor) y oriental (plataforma de Santanyí) de Mallorca, a lo largo de más de 75 km de línea de costa, afectando a las rocas carbonáticas del Mioceno superior. El estudio se ha centrado en la distribución geográfica, evolución geológica y las características geomorfológicas de estos paleocolapsos, con especial énfasis en su génesis, su relación con la arquitectura y distribución de las facies, así como en las formas y productos asociados.

Los paleocolapsos han sido descritos en su contexto litoestratigráfico y estructural dentro de las mencionadas plataformas carbonáticas, siendo este trabajo una contribución al conocimiento del karst en estas unidades geológicas y su relación con las fluctuaciones marinas. La karstogénesis queda reflejada en estas formas pretéritas donde se han observado depósitos y formas de disolución ligadas a la dinámica kárstica controlada, en el caso que nos ocupa, por las fluctuaciones del nivel del mar: brechas, sedimentos detríticos, cementos, así como distintos tipos y volúmenes de porosidad. La mayor parte de estas formas (sobre un total de 177), cuyas dimensiones en sección varían desde pocos metros hasta afloramientos con 28 m de altura y más de 100 m en la horizontal, se ubican en la plataforma de Santanyí a excepción de dos estructuras ubicadas en la plataforma de Llucmajor.

El análisis geológico y su relación con los paleocolapsos muestra como en la plataforma de Llucmajor éstos afectan a las facies de la Unidad Complejo Arrecifal (facies de back reef y frente arrecifal). Sin embargo, en la plataforma de Santanyí, los paleocolapsos afectan tanto a parte del Complejo Arrecifal (facies de back reef), como a la totalidad de la Unidad Calizas de Santanyí. A partir del estudio de la arquitectura de facies del Complejo Arrecifal en la plataforma de Llucmajor se ha establecido el modelo deposicional en la plataforma de Santanyí. Sin embargo, ésta última se encuentra compartimentada como consecuencia del control de dos fallas en dirección de orientación E-O en S'Algar y Na Magrana, donde se localiza el contacto entre facies de lagoon externo y talud arrecifal. No obstante, la cartografía y análisis de los lineamientos en dicha plataforma ha permitido identificar dos familias principales con dos direcciones dominantes; NE-SO y NO-SE, siendo la dirección E-O menos representativa. Se han observado fracturas distensivas y pequeñas fallas inversas miocenas asociadas al proceso de colapso, así como fracturas y fallas postmiocenas, y fracturas cuaternarias.

El estudio de la geometría en sección de los paleocolapsos pone de relieve que la formas en "V", "U" y conoidales son las más comunes. Han sido identificadas dos partes diferentes en un paleocolapso tipo: una inferior donde se observa la paleocavidad ubicada en la base del paleocolapso (lagoon externo y/o frente arrecifal), con una geometría irregular de dimensiones entre 1 m y 9 m rellena por sedimentos adyacentes y suprayacentes a ésta; y una parte superior, coincidente con los bordes de la estructura (lagoon interno/Calizas de Santanyí) buzando con inflexión conoidal hacia la paleocavidad.

Se han identificado cuatro tipos de brechas (crackle, crackle-laminae-split, de mosaico y caótica) en las estructuras de paleocolapso asociadas cada una de ellas a distintos niveles estratigráficos y, en algunos paleocolapsos, con una gradación vertical y lateral. Son característicos de estos depósitos los sedimentos detríticos (matriz) y los cementos asociados (vadosos y freáticos). En general, el cemento domina sobre la matriz en la zona inferior del paleocolapso, mientras que por encima, es la matriz la que domina sobre el cemento. El análisis por difracción de Rayos X de la matriz indica para la muestra total que la calcita es el mineral principal y el cuarzo el mineral secundario. En la fracción arcilla, la moscovita, la illita y la caolinita son los minerales más comunes. De ello, junto con el estudio de láminas delgadas en estos depósitos, donde se han observado tamaños de grano en el cuarzo superior a 2 mm, se deduce un ambiente de sedimentación subsuperfical y otro subaéreo de lo que se extrae un origen, proceso de transporte y sedimentación diversos, así como la evolución cristaloquímica en determinados minerales. Los cementos son de naturaleza calcítica, con contenidos relativamente altos en magnesio para los freáticos y bajos para los vadosos. Para el estudio de la porosidad en los paleocolapsos se ha procedido a su clasificación en dos tipos principales, interclasto e intraclasto, a partir de las cuales se ha estudiado la macro y microporosidad. La brecha caótica de colapso es la que presenta volúmenes de porosidad más elevados y tipologías diversas.

El análisis de isótopos estables muestra una gran homogeneidad entre la composición isotópica de los cementos, con valores en δ18O y δ13C ligeros, lo que indica condiciones análogas de precipitación, con dominio de aguas dulces sobre las saladas. Tanto la marca del oxígeno como del carbono parecen indicar que los cementos se depositaron en un período interglaciar coincidente con algún estadio isotópico impar.

El estudio de la arquitectura de facies de la plataforma de Llucmajor ha permitido elaborar un modelo genético de ocurrencia para los paleocolapsos y su ubicación espacio-temporal. Dicho modelo, ha sido corroborado por la relación entre la distribución de facies y paleocolapsos en la plataforma de Santanyí, por la observación en algunos paleocolapsos de sedimentos a techo de la Unidad Calizas de Santanyí que sellan la estructura, así como por el tipo de brechas características de colapsos sinsedimentarios (brecha crackle-laminae-split), que muestran una deformación dúctil de los materiales cuando éstos no estaban completamente consolidados, dando lugar a formas laxas de bajo ángulo. Los procesos genéticos que dieron lugar a los paleocolapsos kársticos están directamente relacionados con la alta frecuencia de fluctuación del nivel del mar durante el Mioceno superior, la misma que controló la arquitectura de facies y la posición del nivel freático. Las oscilaciones del nivel freático causaron la alternancia de dominios freáticos y vadosos así como, de agua dulce y agua salada en la interfase, provocando la disolución de los parches coralinos y el posterior hundimiento del techo de las cavidades.

El estudio integral de todos estos aspectos junto con el análisis de una red de paleocauces y una playa fósil, ha permitido realizar una reconstrucción paleogeográfica desde el Messiniense en la plataforma de Santanyí e identificar estructuras de paleocolapso postmiocenas y cuaternarias. Con estos datos se ha procedido a la comparación de los paleocolapsos kársticos con otras estructuras similares en el País Vasco y Las Islas de Malta, de lo que se extraen analogías y diferencias, determinadas fundamentalmente por el orden de fluctuación del nivel del mar.

Por último, se discute el papel de los paleocolapsos kársticos como elementos que contribuyen en cierta medida a la ocurrencia de hidrocarburos en plataformas carbonáticas, pudiendo ser excelentes reservorios debido al gran número de afloramientos, el volumen de roca afectada y a su elevada porosidad y permeabilidad.
Paleokarst tend to differ from studies of recent and modern karst landforms though is important the genetic understanding of the karst processes for analysis a paleokarst structure. Paleokarst systems form an important class of carbonate record and they have a pronounced lateral and vertical spatial complexity that results from a complex history of formation. Most of the known karst systems are epigenetic and they are the result of near-surface karst processes during periods of subaerial exposure and latter burial compaction and diagénesis. Scale, porosity types and spatial complexities of these paleokarst systems depends on the carbonate rock solubility, paleoclimatic conditions, lowering of base level either by tectonic uplift or sea-level fall and time of subaerial exposure. Uplift, in addition, commonly induces fracturing and faulting that further control karst development. Ascertaining and predicting paleokarstic heterogeneities within carbonate rocks are strategic to fluids field development and optimum production. With current subsurface methods, however, most of the smaller-scale stratigraphic architecture and diagenetic facies are difficult to define. Predictive models for exploration and development are best made from outcrop studies of well-exposed examples. Accuracy for prediction of these models depends on the detailed understanding of the genetic factors controlling their geometries, scale, pore networks and spatial complexities of these potential karstic store. Miocene carbonates (Upper Tortonian-Lower Messinian) in Mallorca Island are composed of reefal (Reef Complex) and shallow water carbonates (Santanyí Limestone) that prograded across platforms surrounding paleoislands. The contact between the Reef Complex and the Santanyí Limestone is a subaerial erosion surface with paleokarst features. The shallow-water carbonates beds both the lagoonal beds of the Reef Complex and basal beds of the Santanyí Limestone, are affected by paleocollapse structures produced by roof collapse of caverns developed in the underlying Reefal Complex. These paleocollapse structures affecting to the carbonate platform allows to propose a genetic model to explain the origin of these paleosink, that are related to early diagenetic processes induced by high-frequency sea-level fluctuations, the same sea-level fluctuations that controlled the facies architecture of the carbonate platforms.

Cartography and study of lineaments and fractures on Santanyí Platform have permitted identified two principals groups with two main directions: NE-SO and NO-SE. Have been observed distensiva fractures and Miocene small inverse faults related with de breackdwon phenomena. Moreover, postmiocenes and quaternary faults and fractures have been recognized.

The geometry of paleocollapse structures is commonly (in section) as "V", "U" or funnel. The size is variable from few meters of long to thousands meters, and few meters of weigh to thirteen meters. Breccias has been classified as crackle, crackle-laminae-split, mosaic and chaotic types. Chaotic breccias grade from matrix-free, clasts-supported breccias to matrix-supported breccias. The matrix mineralogy is compose in the total sample for calcite in the major part and quartz in less quantity. However, same structures present quartz as principal mineral. To the clay fraction, caolinite, illite and moscovite are the most general mineral present.

The geochimical sediment (carbonate) are filling a part of interclaste breccias porosity. This is commonly phreatic speleothems. Isotopic studies of this sediments show δ18O and δ13C contents negatives. This fact could indicate a fresh water environment deposition

A limited number of laboratory studies and pilot programs have been reported in chemical Enhanced Oil Recovery (EOR) flooding of carbonate reservoirs (Adams & Schievelbein, 1987). Fewer still have involved surfactants in limestone reservoirs. No surfactant/polymer flood on a field wide basis of a carbonate reservoir has ever been documented in the literature (Manrique, Muci, & Gurfinkel, 2010). This void represents a colossal opportunity given that nearly a third of the 32 billion barrels of oil consumed in the world each year come from carbonate reservoirs (Sheng, 2011, pp. 1, 254). This thesis is based on experiments with a high hardness (~5,000 ppm divalent ions) carbonate field. Phase behavior, aqueous stability, and core flood experiments were performed using polymer and various surfactants and co-solvents. Both commercially available and laboratory synthesized surfactants were tested. The objective was to optimize the chemical injection design in order to lower interfacial tension between water and oil in the reservoir. Research was also done with alkali intended for use with hard brines. The main challenges when working with hard brine were poor solubilization and low aqueous stability limits. However, highly propoxylated and ethoxylated surfactants mixed with internal olefin sulfonates, hydrophilic sulfates, and sec-butanol were observed to have very high solubilization ratios, fast phase behavior equilibration times, negligible viscous macroemulsion effects, and excellent aqueous stability. Spinning drop interfacial tensiometer tests confirmed low IFT values were obtained for a range of acceptable salinities with hard brine. Three core floods were performed using one of the surfactant formulations developed. One flood was done with field core, brine, and crude oil and failed to meet expectations because of high levels of heterogeneity (vugs) within the core that lead to an elongated oil bank and low and slow oil recovery. The other floods were done with Estillades Limestone. The first Estillades flood used hard synthetic field brine and had better mobility but poor oil recovery. The last core flood had good mobility and recovered 90% of the residual oil to water flooding, but only after a total of 1.1 pore volumes of 1.0 wt% surfactant solution were injected. The results provided in this thesis constitute proof of concept that S/P flooding can be done in high salinity and hardness reservoirs.
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In geschichteten Reservoiren mit geringer Matrix-Permeabilität kontrollieren überwiegend Bruchsysteme den Fluidtransport. In Kalk-Mergel-Wechselfolgen sind allerdings die vertikale Kluftausbreitung sowie die Vernetzung der Kluftsysteme zwischen den unterschiedlichen Schichten sehr variabel, was schließlich die Permeabilität in diesen bruchkontrollierten Reservoiren erheblich beeinflusst. Innerhalb einer Schichtfolge führen diverse sedimentologische Merkmale (z.B. sedimentäre Schichtung und diagenetische Bankung) zu kontrastreichen Gesteinseigenschaften und wirken somit als Spannungsbarrieren. Spannungsbarrieren, wie beispielsweise lithologische Kontakte oder mächtige Mergellagen, können die Kluftausbreitung in geschichteten Gesteinen ebenfalls verhindern und erschweren zusätzlich die Vorhersage potentieller Fluidwege. Aufgrund dessen ist es entscheidend Schichten, die sich mechanisch einheitlich verhalten („mechanische Einheit“) zu finden. Das Ziel dieser Doktorarbeit ist, den Einfluss von sedimentologischen und diagenetischen Merkmalen und petrophysikalischen Eigenschaften vertikaler Kluftausbreitung in Kalk-Mergel-Wechselfolgen der Jurassischen Blue Lias Formation (Bristol Channel Becken, Großbritannien) abzuschätzen, um verschiedenartige Spannungsbarrieren und mechanische Einheiten zu definieren. Zu diesem Zweck wurden sechs Profile untersucht, welche sich durch unterschiedliche morphologische Variationen auszeichnen (d.h. von kalkdominiert zu mergeldominiert). Die Untersuchungen umfassen Kombinationen aus sedimentologischer (z.B. Geländeuntersuchungen, Dünnschliffpetrografie, Rasterelektronenmikroskopie, CaCO3- and Corg-Messungen), quantitativ strukturgeologischer (z.B. Charakterisierung von Kluftsystemen) sowie petrophysikalischer Daten (z.B. Spaltzug- und Druckfestigkeits-, Rückprallhärte- und Porositäts-Messungen). Im Rahmen der quantitativen strukturgeologischen Untersuchungen wurden unter Verwendung einer modifizierten Scanline Methode (Durchführung einer flächengestützten Kluftanalyse) über 4000 schichtübergreifende Klüfte betrachtet. Generell wird angenommen, dass der Kluftabstand mit zunehmender Bankmächtigkeit zunimmt und die Kluftdichte dementsprechend abnimmt. Diese Studie zeigt jedoch, dass dieser Zusammenhang nur eingeschränkt auf Kalkbänke dieser Abfolgen anwendbar ist und nur auf Schichten mit lateral planaren Oberflächen (wohlgebankte Kalkbänke) übertragen werden kann. Bei Bänken gleicher Mächtigkeit mit allerdings irregulären Oberflächen (semiknollige Kalkbänke) variieren die Kluftabstände innerhalb dieser Bänke beträchtlich. Das bedeutet, die Kluftabstände sind in semiknolligen Kalkbänken eher unregelmäßig wohingegen die Abstände in wohlgebankten Bänken eher regelmäßig sind. Des Weiteren sind in wohlgebankten Kalken ein höherer prozentualer Anteil von schichtgebundenen Klüften (57 %) ausgebildet. Dagegen sind in semiknolligen Kalken ein höherer Anteil nicht-schichtgebundener Klüfte ausgebildet (67 %). Entscheidend für die Kluftausbreitung in geschichteten Gesteinen ist nicht nur die Kluftverteilung der einzelnen Bänke, sondern auch verschiedenartige Spannungsbarrieren, wie beispielsweise lithologische Kontakte, Mächtigkeiten und Heterogenitäten von Mergeln hemmen die Kluftausbreitung. Anhand der vertikalen Kluftstoppung an lithologischen Kontakten und vertikale Kluftausbreitung durch Schichten wurden Spannungsbarrieren identifiziert (schichtgebundene vs. nicht-schichtgebundene Klüfte). Da nicht alle lithologische Kontakte die Ausbreitung von Klüften in geschichteten Gesteinen verhindern, wurde in dieser Studie der Terminus für 50 % Kluftstoppung an diesen Kontakten verwendet („mechanische Grenzflächen“). Zusätzlich wurden bestimmte Mergellagen, die >0.20 m mächtig sind, durch mechanische Grenzflächen begrenzt sind und weniger als 50 % nicht-schichtgebundene Klüfte beinhalten, als „mechanische Puffer“ definiert. Die Charakterisierung des Kluftsystems wird neben der vorherrschenden stark heterogenen Kluftverteilung in der Blue Lias Formation, auch durch eine signifikante Variation des Diagenese-Einflusses von Abschnitt zu Abschnitt erschwert. Beispielsweise wurden in Wales drei Teilprofile genauestens untersucht, welche trotz ihrer räumlich nahen Lage und relativ zeitgleichen Entstehung unterschiedliche sedimentologische und diagenetische Merkmale in Meter- bis Mikrometer-Skalen aufweisen (von früh lithifiziert bis physikalisch kompaktierte Abfolgen). Darüber hinaus sind diese durch unterschiedliche Muster der Kluftstoppung an Kontakten und Kluftausbreitung innerhalb der Bänke charakterisiert. Lithologische Kontakte in diagenetisch beeinflussten Abfolgen sind tendenziell eher graduell und somit keine mechanischen Grenzflächen. Wenn zusätzlich der Unterschied zwischen den CaCO3-Konzentrationen zwischen Kalken und Mergeln niedrig ist, kann die Abfolge als eine mechanische Einheit definiert werden, welches die Kluftausbreitung begünstigen würde. Die Vorhersage der Konnektivität von Kluftnetzwerken ist in lithologisch heterogenen Kalk-Mergel-Wechselfolgen, wie die in der Blue Lias Formation, aufgrund unterschiedlicher Kluftverteilung innerhalb einzelner Bänke, unterschiedliche diagenetische Einfluss und verschiedenartiger Spannungsbarrieren schwierig. Das ist insbesondere für die Charakterisierung der Kluftnetzwerke und ihre Nutzung in Aufschluss-Analogstudien problematisch, welche für die Einschätzung des Fluidtransports in solchen Systemen verwendet wird. Die Ergebnisse dieser Studie sind zur Optimierung der Quantifizierung von Kluftverteilung und -ausbreitung in heterogenen Gesteinsabfolgen entscheidend und präzisieren die Definition mechanischer Einheiten. Diese Definition ist eine wichtige Voraussetzung für die Vorhersage von Kluftpermeabilitäten und folglich entscheidend für Fluidtransportmodelle.

Le stockage géologique est aujourd'hui envisagé dans plusieurs domaines tels que le stockage de CO2 ou celui de déchets nucléaires. C'est un projet à long terme qui nécessite un protocole d'étude particulier afin de déterminer et comprendre la formation envisagée, notamment en termes de mécanismes de transports. Les formations étudiées sont fonction du type de stockage dans le sens où un stockage de gaz ou de déchet radioactifs ne vont pas requérir les mêmes besoins. Dans le cas d'un stockage de CO2, la formation hôte doit posséder de bonnes propriétés réservoirs afin de, notamment, faciliter l'injection. Pour un stockage de déchets radioactifs, la formation hôte doit retenir au maximum les éventuelles fuites de fluides contaminés, c'est pourquoi les sites de stockage envisagés sont au sein de formation très peu poreuse et très peu perméable, argilite ou granite notamment.Les travaux présentés dans cette thèse sont liés à deux projets de stockage. Le premier a pour but l'étude pétrophysique d'une formation potentiellement hôte d'un stockage de CO2 dans le Bassin Parisien, la formation carbonatée de l'Oolithe Blanche. Cette formation, composée de trois faciès principaux, présente de faibles propriétés réservoir qui sont influencées par trois paramètres microstructuraux : la nature du liant, la quantité de compaction et, enfin, la taille des pores et leur distribution.Le second projet est basé sur l'étude d'un analogue structurale au laboratoire de Meuse/Haute-Marne de l'Andra pour le stockage de déchets radioactifs. Cet analogue est situé dans l'archipel Maltais, qui présente une structure tabulaire très proche de celle observée dans la région du laboratoire de Meuse/Haute-Marne : calcaire/argile/calcaire. Notre étude a permis la mise en évidence de plusieurs périodes de mouvement de fluides oxydants, dont une traversant l'ensemble de la formation argileuse, remettant ainsi en cause ses propriétés d'imperméabilité
Geological storage is now considered as a technical solution for CO2 storage andnuclear waste management (for high-level and intermediate-level long-lived radioactivewaste). A geological storage is a long term project which implies a particular protocol in orderto better determine and to better understand the host rock, especially in terms of transportmechanisms. The geological formations studied are chosen in function of their storagecapacity because gas storage or nuclear waste storage do not need the same requirements.In case of CO2 storage, the host formation must provide good reservoir properties in order tofacilitate the injection. Here, the safety of the storage is guaranteed by traps (structural,residual, mineral) and by the presence of a cap rock. Concerning nuclear waste storage, thehost must retain at best the potential radioactive fluids and gaz leaks, and this is the reasonwhy storage sites are studied within low porous and low permeable formation, like argillite orgranite.The work presented in the PhD thesis is related to two storage projects. The first oneis focused on the petrophysical study of a potential host for CO2 storage in the Paris Basin,the “Oolithe Blanche” carbonate formation. The second project is an analogue study of thesedimentary structure explored in the Meuse/Haute-Marne laboratory. This laboratory isstudied by ANDRA to be the first nuclear waste storage in a deep geological formation inFrance. The analogue was found in maltese archipelagos, which presents almost the sametabular structure as the one observed in the Meuse/Haute-Marne laboratory:limestone/clay/limestone affected by a weak tectonique deformation.In the first part, the Oolithe Blanche Formation study allowed to determine thereservoir properties of the three principals facies of the formation. This study was realized onplugs sampled on quarries in Burgundy (France). Those facies are characterized by differentenvironmental processes and deposit energy; nonetheless, they are all located within ashoreface depositional environment. They are composed of ooids, pellets and bioclasts invarying proportions. The reservoir properties studied showed the Oolithe Blanche Formationis a microporous one. Microstructural parameters which influence reservoir properties are:the cement type (sparite or micrite), amount of compaction characterized by the cementquantity and the contact between elements and, at last, the pore size distribution withinporous elements (micro, meso, macropores).The second part of this project is focused on a more petrophysical study which aimedat characterizing the pore network influence (volume, shape in space) on acoustic velocities,6electrical conductivity and on permeability. The study is completed by the use of permeabilitypredictive models based on mercury porosimetry spectra.The maltese archipelagos study is based on observations made by Missenard et al.(in prep.) .), Rocher et al., (2008) and Missenard et al. (2009, 2011) on the Blue ClayFormation, thick clay formation (~ 100 m) and on the underlying Globigerina Limestone. Theclay formation presents an important fracture network characterized by gypsum filling and byan oxidizing zone near the fractures. A similar oxidation, in the shape of lobes andmushrooms, is observed within the Globigerina Limestone.This study is also divided in two parts. In the first one, the focus is on the study ofgypsum filling fractures. Studying this filling is directly linked with the storage topic, because,in the case of a nuclear waste storage, the absence of fractures and fluid motion is animportant condition to insure the storage security. In the case of gypsums filling, the study isbased on geochemical measurements on oxygen (δ18O), sulphur (δ34S) and strontiumisotopes (87Sr/86Sr) coupled with a fluid inclusion study, all measurements performed ongypsum crystal. Those analyses allow us to propose a downward fluids circulation modelthrought the clays. Fluids source which is at the origin of gypsum’s precipitation seems to beyounger than the hosted formation. Because of the position of the maltese islands, inMediterranean sea, one potential source is the Messinian evaporites, which Sr isotopic ratiocorresponds well to our data set.The second part of the maltese study concerns the oxidation shape observed withinthe Globigerina Limestone. The aim is to determine the processes which allowed thisoxidation. The main question is: are those structures the results of an internal heterogeneityin the rock or the sign of a stop in a fluid motion (stop of the fluid or stop of the oxidizingmechanism)? In order to answer those questions we based our interpretaion on the skeletonof the rock (mineralogy, magnetic mineralogy, microstructural study, geochemistry), on poreand porosity (porosity measurements, mercury porosimetry…), on permeability and on therock anisotropy (susceptibility of magnetic anisotropy (SMA) and acoustic velocitiesanisotropy). Some conflicting differences on the dataset exist, especially on anisotropy data,which can suppose some complex processes