Shale Grains Research Articles

Assessing the effect of oriented structure characteristics of laminated shale on its mechanical behaviour with the aid of nano-indentation and FE-SEM techniques

Variations in the mechanical properties of oriented shale within the nano-to-micro scale are crucial to determine the deformation and fracture of shales. However, the relationships between the oriented structure characteristics of shale and its mechanical properties need further investigation. In this study, the Yan-Chang #7 shale in the Ordos Basin is selected to elucidate the micro-mechanical properties of different shale grains using nano-indentation experiments. Results show that pyrite grains exhibit the highest elastic modulus, followed by quartz, feldspar, calcite, dolomite, clay minerals, and organic matter. Additionally, the experiments demonstrate an abrupt shift at the contact edge of the grains due to high heterogeneity. By applying a modified Mori-Tanaka method, we upscale the micromechanical characteristics of grains to the matrix. The size, flatness of grains, and structure orientation entropy (SOE) of shale indicate a good correlation with the mechanical properties of shale or grains. A larger size, more flatness of grains, and lower SOE result in smaller values of the elastic modulus of shale. The layered structure of shale samples creates a weak surface between the layers, making them more susceptible to fracturing and deformation when subjected to stress.

Potential of carboxymethyl cellulose solution to increase the shale stability

Slope failures in Bangladesh's Chittagong division are a growing concern, with fatalities increasing from 19 in 2000 to 162 in 2017 and projected to rise further. This study aims to identify the most vulnerable rock formation and assess Carboxymethyl Cellulose (CMC) as a solution for enhancing shale strength and mitigating slope failures. The research began by evaluating weathering susceptibility and stability of different rock layers, revealing the high instability of shale in the Bhuban Formation. Slake durability tests measured cation concentration to understand shale instability mechanisms. Laboratory experiments, including immersion tests and grained-and-molded shale specimens, examined CMC's potential to improve shale stability. Results indicated that the shale of the Bhuban Formation had the highest hammer value variations, indicating increased weathering susceptibility. Shale instability was attributed to illite layer dissolution, releasing K+. Intact shale specimens treated with CMC showed enhanced penetration resistance, shear strength, and deformation behavior, suggesting CMC's potential in increasing shale stability. Grained-and-molded shale specimens treated with CMC demonstrated increased shear strength, critical shear displacement, and contraction deformational behavior. Optical microscopy and scanning electron microscopy revealed the formation of cross-links between shale grains, contributing to improved shale stability. Further research is needed to explore the application of CMC for enhancing in situ rock slope stability. This study emphasizes the importance of addressing slope failures in the Chittagong division and provides insights into mitigating the risks through CMC-based interventions.

A quantitative analysis of flow properties and heterogeneity in shale rocks using computed tomography imaging and finite-element based simulation

A quantitative evaluation of flow property influenced by micro-scale heterogeneities in shale rocks is presented. Micro- and nano-Computed Tomography images of shale rock samples obtained from Mancos, Marcellus and Eagle Ford formations are digitised into entities such as shale grains, organic matter (kerogen), shale minerals, pores and micro-cracks. Numerical computation on selected layers and sub-micron divisions of the geometries is then carried out using a computationally efficient finite-element based simulation algorithms. Parameters such as pore-volume distribution, porosity, permeability and heterogeneity factor within and across layers are computed as part of pre- and post-process operations. The results of these flow properties characterisation indicated that some shale samples have micro cracks while some do not have. Meanwhile, the presence of micro-cracks in the shale samples contributed to the observed wide variation in permeability and porosity. The static characterisation revealed that different shale rock samples will have different morphological properties. The highest variance in permeability within a layer is of magnitude 5 in Eagle Ford while a magnitude of 2 was computed for Mancos perpendicular. However, magnitudes of 1 and 4 are recorded across layers for Mancos perpendicular and Eagle Ford perpendicular respectively. Contrary to existing assumption that heterogeneity at pore-scale is negligible, it is established from the aforementioned analysis that micro-scale heterogeneity can be quantified. Furthermore, through the analysis of variance and root-mean-square values, it was concluded that tortuosity is inversely related to porosity, permeability and their degree of heterogeneity.

Application of the Grain-Based Rock-Eval Pyrolysis Method to Evaluate Hydrocarbon Generation, Expulsion, and Retention of Lacustrine Shale

The study on hydrocarbon generation, expulsion, and retention of shale is becoming more and more important as the exploration of unconventional oil and gas worldwide. There are multiple sets of lacustrine shales in the eastern area of China, which show a great potential for shale oil/gas exploration. In this study, a grain-based Rock-Eval pyrolysis method was conducted on three sets of lacustrine shales, including the Nenjiang shale, Shahejie shale, and Maoming oil shale, to evaluate the hydrocarbon generation, expulsion, and retention. For comparison, pyrolysis of kerogen from the three shale samples was also carried out under the same experimental conditions. The Maoming oil shale showed a slightly broader distribution of activation energies than the Nenjiang and Shahejie shales, while the Nenjiang shale showed higher dominant activation energy than the Shahejie shale and the Maoming oil shale. At laboratory heating rates (5–25°C/min), the corresponding temperature to the maximum hydrocarbon generating rate of shale grains was collectively higher than that of their kerogen, especially for the Nenjiang and Shahejie shales, which implies a lagging effect during the hydrocarbon generation and expulsion process for the shales. By calculating the differences in hydrocarbon yields between shale grain and kerogen samples, the content and proportion of the retained hydrocarbons were measured at different maturation stages. The results showed that the Nenjiang shale from the Songliao Basin has the strongest retention ability but the weakest expulsion ability, whereas the Shahejie shale from the Dongying Depression has the strongest expulsion ability but the weakest retention ability among the three samples. Moreover, it is found that the pore structure of lacustrine shales is likely the principal factor controlling the hydrocarbon retention ability/capacity. This study is expected to provide a geochemical quantitative basis for evaluating hydrocarbon generation, expulsion, and retention of shale.

Evolution of Shale Permeability under the Influence of Gas Diffusion from the Fracture Wall into the Matrix

Permeability is the most important property that controls the transfer of gas mass across a hierarchy of scales within a shale gas reservoir. When gas diffuses from the fracture wall into the matrix, the gas adsorbs onto shale grains. This adsorption may result in matrix swelling. In previous studies, it is commonly assumed that this swelling is uniform within the matrix. Under this assumption, the impact of the gas diffusion process would be neglectable. In this study, we hypothesize that this uniform swelling assumption is responsible for the inconsistencies between poroelastic solutions and experimental or field observations as reported in the literature. We introduce a volumetric ratio of the gas-invaded volume to the whole matrix volume to quantify the impact of matrix swelling volume expansion on the evolution of shale permeability. The gradual matrix pressure increase in the vicinity of fracture walls leads to local swelling. As the gas invaded zone expands within the matrix, the local effect weakens. When the matrix is completely invaded by the injected gas, a new homogeneous state is achieved, and the local effect ends. We find that the evolution of shale permeability from initial to final homogeneous states is a result of the propagation of the gas invaded area. We apply this approach to generate a series of shale permeability maps. These maps explain experimental observations under a spectrum of conditions from constant confining pressure, to constant average pore pressure, to constant effective stress, and to constant total volume conditions.

Resistivity dispersion in pyrite-bearing shaly sandstones

In pyrite-bearing shaly sandstones, the distortion in the resistivity logging response of formations in high-frequency resistivity logging because of dispersion hinders the calculation of reservoir saturation. To eliminate the effect of resistivity dispersion of pyrite and shale, and to avoid factors, such as mineral composition, content, and distribution in natural cores, we synthesized twelve samples with dispersed pyrite and shale grains at high temperature and pressure (60 MPa and 120 °C). We performed experiments at different water salinities and oil saturations, and different frequency to assess the effect of frequency on the conductivity of pyrite-bearing shaly sandstones. Both the dispersed pyrite and shale grains show dispersion, and the real part of the complex resistivity decreases with increasing frequency. Based on symmetrical effective medium conductivity theory and the experimental data, the effective medium dispersion model for the real part of the complex resistivity for pyrite-bearing shaly sandstones is established considering the effect of pyrite and shale content on resistivity dispersion. Simulations suggest that the predicted resistivity dispersion by the model in pyrite-bearing shaly sandstones for variable frequency, and pyrite and shale content agrees with the experimental results. The proposed model can successfully predict the dispersion of pyrite-bearing shaly sandstones. Finally, the resistivity dispersion correction plot for the conductivity of pyrite and shale grains of 0.062 S/m and 0.031 S/m, respectively, is established based on the frequency applied to various electric logs, and the correction method for the high-frequency resistivity log response is given to obtain the real formation resistivity.

Advances in Elemental Spectroscopy Logging: A Cased Hole Application Offshore West Africa

Rising costs for exploration and developments and more stringent need to secure any additional drop of oil have put operators’ margins under increasing pressure. Coupled with the recent oil price decline, this call for efficiency and diligence to be the main drivers for any formation evaluation and planning for development and production. The reservoirs in Western offshore Africa are so diverse in the settings that two reservoirs hardly show any correlation. The complexity associated with the Rifting of African plate from South American plate has introduced significant geological challenges, adding to even bigger challenges in Petrophysical analysis. The mineralogy is complex; clay characterization is often unsolved. The formation waters are fresh with variable salinity and there is occurrence of thin shale laminations and grain size variations contributing to low resistivity low contrast pay generation. Advanced and fit-to-purpose logging technologies and computational methods are needed for rock quality and potential. Moreover, in some cases the accessibility of the target reservoir is difficult and risky, so that formation evaluation must be performed behind casing.The high definition spectroscopy tool is the latest development in wireline spectroscopy measurements. Its technological advances revolutionize the neutron-induced gamma ray methodology to support robust lithology and saturation interpretation in formations with complex mineralogy and fluid content. The ability to determine both the matrix mineral composition and total organic carbon (TOC) are instrumental to the geoscientist, the petrophysicist, the reservoir engineer, and the completion engineer. In the region, the use of high definition spectroscopy measurement has been pioneered while pursuing better understanding of rock composition and more accurate reservoir models in complex lithology and fresh formation waters with low resistivity contrast. The results are beneficial at the various stages of a field development and provide critical input to the petrophysical reserves estimate.In the example described in this paper, the new technology has proven to be critical to evaluate a complex reservoir system independent of the water salinity and resistivity offshore Gulf of Guinea, even with logging behind casing. A comprehensive set of quality outputs is made available for accurate reservoir quality; the logs data processing is performed within the critical-hours after logging to enable informed decision making.

Water Saturation Relations and Their Diffusion‐Limited Equilibration in Gas Shale: Implications for Gas Flow in Unconventional Reservoirs

AbstractLarge volumes of water are used for hydraulic fracturing of low permeability shale reservoirs to stimulate gas production, with most of the water remaining unrecovered and distributed in a poorly understood manner within stimulated regions. Because water partitioning into shale pores controls gas release, we measured the water saturation dependence on relative humidity (rh) and capillary pressure (Pc) for imbibition (adsorption) as well as drainage (desorption) on samples of Woodford Shale. Experiments and modeling of water vapor adsorption into shale laminae at rh = 0.31 demonstrated that long times are needed to characterize equilibrium in larger (5 mm thick) pieces of shales, and yielded effective diffusion coefficients from 9 × 10−9 to 3 × 10−8 m2 s−1, similar in magnitude to the literature values for typical low porosity and low permeability rocks. Most of the experiments, conducted at 50°C on crushed shale grains in order to facilitate rapid equilibration, showed significant saturation hysteresis, and that very large Pc (∼1 MPa) are required to drain the shales. These results quantify the severity of the water blocking problem, and suggest that gas production from unconventional reservoirs is largely associated with stimulated regions that have had little or no exposure to injected water. Gravity drainage of water from fractures residing above horizontal wells reconciles gas production in the presence of largely unrecovered injected water, and is discussed in the broader context of unsaturated flow in fractures.

Pore-scale analyses of heterogeneity and representative elementary volume for unconventional shale rocks using statistical tools

A statistical technique for the pore-scale analyses of heterogeneity and representative elemental volume (REV) in unconventional shale rocks is hereby presented. First, core samples were obtained from shale formations. The images were scanned using microcomputed tomography (micro-CT) machine at 6.7 μm resolution with voxels of 990 × 990 × 1000. These were then processed, digitised, thresholded, segmented and features captured using numerical algorithms. This allows the segmentation of each sample into four distinct morphological entities consisting of pores, organic matter, shale grains and minerals. In order to analyse the degree of heterogeneity, Eagle Ford parallel sample was further cropped into 96 subsamples. Descriptive statistical approach was then used to evaluate the existence of heterogeneity within the subsamples. Furthermore, the Eagle Ford parallel and perpendicular samples were analysed for volumetric entities representative of the petrophysical variable, porosity, using corner point cropping technique. The results of porosity REV for Eagle ford parallel and perpendicular indicated sample representation at 300 μm voxel edge. Both pore volume distribution and descriptive statistical analyses suggested that a wide variation of heterogeneity exists at this scale of investigation. Furthermore, this experiment allows for adequate extraction of necessary information and structural parameters for pore-scale modelling and simulation. Additional studies focusing on re-evaluation at higher resolution are recommended.

Separation of

ABSTRACTA large amount of fine granular materials (<6 mm) are produced during the mining of oil shale. The combustion characteristics of oil shale improve with decreasing size of these materials, for which reason fine-grain oil shale has a high utility value. However, fine oil shale also contains a significant amount of inorganic mineral impurities which can be reduced by physical separation to improve the oil quality. Based on an analysis of the physical properties of oil shale, this paper proposes a compound dry separation process for the cleaning of <6 mm oil shale grains. The effects of the vibration intensity, air velocity, and back angle of the employed separator on the separation results and oil content of the cleaned oil shale were systematically analyzed. Under the optimal vibrational conditions defined by a vibration intensity of 25.76 (amplitude = 4.0 mm, frequency = 40 Hz), air velocity of 0.66 m/s, and back angle of 45°, the yield comprised 35.8% concentrate and 64.2% tailings, with corresponding oil contents of 10.02% and 0.85%, respectively. The probable error of the highest intensity of segregation achieved was 0.155. The proposed compound dry separation of oil shale particles of up to 6 mm was found to be more efficient compared with conventional methods, and the separated fine grade material can be comprehensively utilized by further pyrolysis treatment.

Kinetic study of marine and lacustrine shale grains using Rock-Eval pyrolysis: Implications to hydrocarbon generation, retention and expulsion

The kinetic parameters of marine and lacustrine shale grains (4 mm) were retrieved by using Rock-Eval pyrolysis in comparison with finely ground powder (<0.178 mm) and kerogen of same samples. Results of grains show remarkable differences from powder and kerogen. Grains of Pingliang marine shale exhibit a relatively broader distribution of activation energies than powder and kerogen while grains of Yanchang lacustrine shale show higher dominant activation energies than powder and kerogen. At laboratory heating rates (5–25 °C/min), the corresponding temperatures to the maximum hydrocarbon generating rate of grains are 3–8 °C higher than powder and kerogen for marine shale and 6–8 °C higher for lacustrine shale, respectively. Extrapolated to geological heating rate (3 °C/my), the corresponding maturity and geological temperature to the maximum hydrocarbon expulsion rate of grains lags powder 0.02 Ro% and 3 °C, as well as 0.05 Ro% and 6 °C for marine shale and lacustrine shale, respectively. After the peak of hydrocarbon generation (Ro = 1%), the retention percentage for grain and powder of marine shale reach 7.33% and 0.09% while those for lacustrine shale reach 16.50% and 10.85%, respectively. These results suggest grains enjoy higher expulsion threshold and higher retention ability. The results suggest that Yanchang lacustrine shale exhibits stronger retention ability and weaker expulsion ability than Pingliang marine shale. The results presented in this study show that grain-based pyrolysis provides a novel method for evaluating the residual oil and gases for shale, which can study the hydrocarbon generation, expulsion and retention comprehensively.

Frictional properties of shale reservoir rocks

AbstractWe performed laboratory friction experiments on shale samples from three hydrocarbon reservoirs to assess compositional controls on fault slip behavior accompanying hydraulic stimulation. The samples span a range of clay and total organic content from ~10 to 60% by weight and demonstrate fine‐scale heterogeneity within each reservoir. Friction measurements demonstrate strong dependence of strength and rate‐state constitutive properties on shale composition. Shale samples with clay and organic content above ~30% by weight show coefficient of friction ~0.4 and consistently velocity‐strengthening behavior, while those below this threshold show increased strength and velocity‐weakening behavior. This transition in frictional strength and stability suggests a change in the shale grain packing framework from rigid clast supported to clay mineral and organic matter supported. Measurements of gouge dilatancy further support these relationships, showing a negative correlation with clay and organic content. Critical slip evolution distance exhibits similar dependence on composition, implying common micromechanical mechanisms for the observed transition in frictional behavior. We performed microstructural characterization of the experimental samples and observe changes in the gouge load‐bearing framework and shear localization features consistent with these mechanical data. While these results can be applied generally to infer slip stability on faults in clay‐bearing sedimentary rock, we employ the experimental data to place constraints on microearthquake magnitudes and the occurrence of slow shear slip on preexisting faults during hydraulic stimulation in shale reservoirs.

Geostatistical modeling of clay spatial distribution in siliciclastic rock samples using the plurigaussian simulation method

In order to implement secondary and enhanced oil recovery processes in complex terrigenous formations as is usual in turbidite deposits, a precise knowledge of the spatial distribution of shale grains is a crucial element for the fluid flow prediction. The reason of this is that the interaction of water with shale grains can significantly modify their size and/or shape, which in turn would cause porous space sealing with the subsequent impact in the flow. In this work, a methodology for stochastic simulations of spatial grains distributions obtained from scanning electron microscopy images of siliciclastic rock samples is proposed. The aim of the methodology is to obtain stochastic models would let us investigate the shale grain behavior under various physico-chemical interactions and flux regimes, which in turn, will help us get effective petrophysical properties (porosity and permeability) at core scale. For stochastic spatial grains simulations a plurigaussian method is applied, which is based on the truncation of several standard Gaussian random functions. This approach is very flexible, since it allows to simultaneously manage the proportions of each grain category in a very general manner and to rigorously handle their spatial dependency relationships in the case of two or more grain categories. The obtained results show that the stochastically simulated porous media using the plurigaussian method adequately reproduces the proportions, basic statistics and sizes of the pore structures present in the studied reference images.

Experimental Research on Mixing and Motion with Discontinuous Feed for Oil Shale Particle Groups in Rotary Kiln

A series of experiments were carried out to explore the characteristics and mixing of oil shale grains with diameter of 0∼12mm in rotary kiln. Influence of rotational speed, filling degree and lifting flights forms on mixing efficiency were analyzed. Results showed particle group movement traces and mixing process was significantly affected by the filling degree, the rotational speed and the lifting flight forms. With the increase of filling rate, the particle size was easily to produce separate effects; however, with the decrease in speed, the mixing of particle size with rectangular lifting flight was better than that of straight alifting flight.

Approaches to the Determination of Oil Content in Oil Shale

Oil and gas are important energy minerals and strategic resources. Moreover, as their substitute, oil shale is the non-renewable fossil fuel resource. In this paper, regarding the oil shale of Huadian in Jilin Province as raw material, we made a research on the approaches to extracting shale oil from oil shale as well as an experimental determination on the impact of heating temperature, shale grain size and holding time.

Thermal and mechanical characterization of polymer composites filled with dispersed zeolite and oil shale

The thermal, viscoelastic, mechanical behavior of polymers filled with dispersed zeolite and oil shale is studied as a function of temperature, grain size, and filler concentration. It was found that the thermal conductivity of epoxy—zeolite composite increases with different zeolite grain sizes and takes a higher value in case of the 63 μm grain size composite. The observed enhancement in the thermal conductivity of zeolite composites correlates well with that of the electrical conductivity. The thermodynamic results exhibit a slight increase in the glass transition temperature of the polystyrene/oil shale composites, and shift in the observed relaxation peaks with increasing the oil shale content. The plastic deformation of PS/oil shale composites shows that the elastic modulus increases and the compressive yield stress decreases with oil shale content. The Eyring theory of yielding could predict the dependence of the yield stress on the applied strain rate. The predicted activation volume and activation energy showed dependence on the oil shale grains sizes and content.

Petrographic Studies of Rocks from The Chesapeake Bay Impact Structure (USA): Implication for Moderate Shock Pressures in Sedimentary Breccias

Shock petrographic investigations were carried out on samples collected from drill cores from the Chesapeake Bay impact structure (USA). The late Eocene Chesapeake impact structure is, at 85 km diameter, currently the largest impact structure known in the United States, buried at shallow to moderate depths beneath continental margin sediments underneath southeastern Virginia. To better define the variety of the samples collected from the shallow drill cores and the shock degrees experienced by the target rocks and breccias in the Chesapeake impact crater, thin section analyses were conducted on more than 50 samples from the various zones of the impact structure. The study involves measurements of the orientations of planar deformation features (PDFs) using a universal stage attached to a petrographic microscope. The aim of this study is to determine the shock pressures of various clasts in the shallow breccia fill of the crater. As a result, we note that the overwhelming numbers of shocked grains, which are now present in the sedimentary breccia, are derived from the basement granitoids. Our studies involved samples from four shallow drill cores (Exmore, Windmill Point, Kiptopeke, and Newsport News).The breccia fill is termed the Exmore breccia, which is dominated by particulates of silt, shocked and unshocked granitic fragments, shale, clay, and free shocked quartz grains. The Kiptopke and Windmill Point samples contained rare fragments showing a variety of different shock effects, whereas the Newporte News samples, show several fragments and impact melt with the evidence shock metamorphism was noted. The most abundantly observed shock indicators are shock fracturing, indicative of shock pressures of less than about 10 GPa, as well as 1-2 sets of PDFs in quartz grains, which is indicative of moderate shock pressures of up to about 20 or 25 GPa. Key words: Chesapeake Bay Crater, PDFs, Shock pressure, Universal stage, Impact structure.

Factors influencing plutonium sorption in shale media

Summary. The extent and factors influencing sorption of plutonium (Pu) in shale media have been studied in batchtype experiments. The equilibrium time and isotherm of Pu sorption have been firstly determined. The effect of shale grain size, aqueous pH, water/solid ratio, co-existing ions (cations and anions) and temperature were studied as the factors likely to influence Pu sorption. The experimental variables included the following: grain sizes in five ranges, 0.12 to 0.15 mm, 0.15 to 0. 18 mm, 0.18 to 0 .25 mm, 0.25 to 0.38 mm, and 0.38 to 0.83 mm; solution pH values of 4, 6, 8, and 10; water/solid ratios of 10 : 0.25, 10 : 0.5, 10 : 0.75, and 10 : 1; temperatures of 20 ◦ C, 40 ◦ C, and 60 ◦ C); and selected coexisting conventional cations including Na + ,F e + ,A l 3+ ,C a 2+ , and K + and anions including SO4 2− ,C O 3 2− ,N O 3 − ,a nd Cl − in each case in solutions of the same total ionic strength. The experimental results demonstrate that the equilibrium time of Pu sorption is 9 d, that the sorption behavior of Pu in the solution is well described by the Freundlich sorption isotherm (Cs = kC N ), and that Pu is strongly sorbed on shale media. The extent of Pu sorption increased with decreasing grain size, apparently in response to the increase in specific surface area and total pore volume. The results also show that Pu sorption increases with increasing solution pH and with increasing water/solid ratio. The influence of co-existing anions on Pu sorption was much stronger, under the same conditions, than that of the cations; this was attributed to Pu complexation in solution, i.e., the complexing apparently weakened the sorption of Pu on shale particles in the solution. Finally, the influence of varying temperature on Pu sorption is found to be less important than that of other factors, but should never be ignored.

Generalized effective medium resistivity model for low resistivity reservoir

With the advancement in oil exploration, producible oil and gas are being found in low resistivity reservoirs, which may otherwise be erroneously thought as water zones from their resistivity. However, the evaluation of low resistivity reservoirs remains difficult from log interpretation. Since low resistivity in hydrocarbon bearing sands can be caused by dispersed clay, laminated shale, conductive matrix grains, microscopic capillary pores and high saline water, a new resistivity model is required for more accurate hydrocarbon saturation prediction for low resistivity formations. Herein, a generalized effective medium resistivity model has been proposed for low resistivity reservoirs, based on experimental measurements on artificial low resistivity shaly sand samples, symmetrical anisotropic effective medium theory for resistivity interpretations, and geneses and conductance mechanisms of low resistivity reservoirs. By analyzing effects of some factors on the proposed model, we show theoretically the model can describe conductance mechanisms of low resistivity reservoirs with five geneses. Also, shale distribution largely affects water saturation predicted by the model. Resistivity index decreases as fraction and conductivity of laminated shale, or fraction of dispersed clay, or conductivity of rock matrix grains increases. Resistivity index decreases as matrix percolation exponent, or percolation rate of capillary bound water increases, and as percolation exponent of capillary bound water, or matrix percolation rate, or free water percolation rate decreases. Rock sample data from low resistivity reservoirs with different geneses and interpretation results for log data show that the proposed model can be applied in low resistivity reservoirs containing high salinity water, dispersed clay, microscopic capillary pores, laminated shale and conductive matrix grains, and thus is considered as a generalized resistivity model for low resistivity reservoir evaluation.

The influence of grain size on the products yield and shale oil composition from the Pyrolysis of Sultani oil shale

In this work, the influence of shale grain size of 0.20–0.60, 0.60–1.20, 1.20–3.33, and 3.33–5.60 mm were carried out on the oil shale pyrolysis in a semi-continuous fluidised bed and 50 gm fixed bed reactor under nitrogen and nitrogen/steam pyrolysis atmosphere. The final pyrolysis temperature was 520 °C, heating rate 12 °C min −1, vapour residence time of 25 and 28 s for the fluidised bed and fixed bed pyrolysis, respectively, and shale residence time of 45 min. The oil yield was increased as the particle grain size was increased from 0.2–0.6 to 3.33–5.6 mm under both nitrogen and nitrogen/steam pyrolysis atmospheres. Increasing the particle grain size caused a decrease in the derived hydrocarbon gases and an increase in the carbon and hydrogen content in the derived oil. Decreasing the particle grain size (in the studied range) caused an increase in the PAH concentration in the derived oil. This increase has been suggested as a result of the aromatisation of the derived oils by the secondary decomposition reactions.