Good Pore Connectivity Research Articles

Method for Predicting Bound Water Saturation in Tight Sandstone Reservoirs Using Morphology and Fractal Models

The nuclear magnetic resonance T2 spectrum was used to identify the T2 cut-off value, which is the key to determining the irreducible water saturation of a reservoir. In this paper, the saturation and centrifugal T2 spectra of sandstone and coal samples were used to explore the correlation between each parameter and the T2 cut-off value, using a single fractal dimension, a multifractal dimension and a spectral morphology discrimination method. The conclusions are as follows: (1) The T2 spectra of nine sandstone samples in this paper can be divided into four types. Type A is represented by sample 2, wherein the T2 spectrum shows a bimodal state and the area of the right T2 spectrum (2.5~100 ms) is larger than that of the left T2 spectrum (T2 < 2.5 ms), indicating that the sample has good pore connectivity and belongs to the macroporous development sample. The B-type T2 spectrum is unimodal, and the pore connectivity is poor, indicating that it is a large-pore development sample. The T2 spectrum of the C-type sample is unimodal, and the pore connectivity is very poor, indicating that it is a mesoporous development sample. The T2 spectrum of the D-type sample shows a single peak state, and the main T2 is distributed within 0.1~2.5 ms. The pore connectivity is very poor, which indicates that it belongs to the small pore development type sample. (2) The single fractal model shows that, compared with other single fractal parameters, D2 increases with the increase in the T2 cut-off value, but the correlation is weak. Therefore, it is not feasible to predict the T2 cut-off value using the single fractal dimension parameter. (3) The multifractal model shows that D−10–D10 increases linearly with the increase in D−10–D0, but there is no obvious linear correlation between D0–D10 and D−10–D10, indicating that the low pore volume area in this kind of sample controls the overall heterogeneity of pore distribution. (4) The related parameters affecting the T2 cut-off value include D−10–D10, D−10/D10, D−10–D0, TM and D2. Therefore, based on the above five parameters, a T2 cut-off value prediction model is constructed. The T2 cut-off value calculated by the model is highly consistent with the experimental value, which proves the reliability of the model.

Sedimentological and petrophysical characterization of the Bokabil Formation in the Surma Basin for CO2 storage capacity estimation

Large-scale geological sequestration of CO2 is one of the most effective strategies to limit global warming to below 2 °C, as recommended by the Intergovernmental Panel on Climate Change (IPCC). Therefore, identifying and characterizing high-quality storage units is crucial. The Surma Basin, with its four-way dip closed structures, high-quality reservoirs, and thick regional cap rocks, is an ideal location for CO2 storage. This study focuses on the Bokabil Formation, the most prominent reservoir unit in the Surma Basin. Detailed petrographic, petrophysical, XRD, and SEM analyses, along with mapping, have been conducted to evaluate the properties of the reservoir and cap rock within this formation. The Upper Bokabil Sandstone in the Surma Basin ranges from 270 to 350 m in thickness and consists of fine- to medium-grained subarkosic sandstones composed of 70–85% quartz and 5–12% feldspar, with good pore connectivity. Petrophysical analysis of data from four gas fields indicates that this unit has a total porosity of 21–27.4% and a low shale volume of 15–27%. Cross plots and outcrop observations suggest that most of the shales are laminated within the reservoir. The regional cap rock, known as the Upper Marine Shale (UMS), ranges in thickness from 40 to 190 m and contains 10–40 nm nano-type pores. A higher proportion of ductile materials with a significant percentage of quartz in the UMS indicates higher capillary entry pressures, enhancing its capacity to hold CO2. Using the CSLF method with a 6% cut-off of the available pore volume, it is estimated that 103 Mt, 110 Mt, 205 Mt, and 164 Mt of CO2 can be effectively stored in the Sylhet, Kailashtila, Habiganj, and Fenchuganj structures, respectively. Due to the shallow depth of the storage unit and the thick cap rock, the southern Surma Basin is the optimal location for CO2 injection.

Effect of the pore structure characteristics of coal samples on the dynamic adsorption of water vapor

In order to study the dynamic adsorption process of water vapor in the pore structure of different coal samples (YJL for lignite, SEK for bituminous coal and BJ for anthracite). The pore structure characteristics of the three coal samples were analyzed by mercuric pressure method, liquid nitrogen adsorption method and infrared spectroscopy. Further, the water vapor adsorption capacity of the three coal samples under different humidity conditions was determined by dynamic water vapor sorption (DVS) experiments. In addition, the monolayer adsorption and multilayer adsorption at different humidity were calculated using the Dent model. The results showed that YJL had the largest surface pore volume and oxygen functional group parameter (IO = 12.41), and its water vapor adsorption capacity was also the highest. However, under high humidity conditions, the presence of a large number of pore throats in the YJL coal samples hindered multilayer adsorption, resulting in a water vapor adsorption percentage of only 18.07 %. On the other hand, SEK has a small oxygen functional group parameter (IO = 5.81), poor pore connectivity, and a certain pore throat structure, resulting in a low water vapor adsorption capacity of SEK coal samples, with a water vapor adsorption proportion of only 23.76 %. BJ coal has a large pore volume and a large number of oxygen functional groups on the surface (IO = 8.84), which has a good pore connectivity and the least number of pore throats structure, resulting in a water vapor adsorption ratio is higher at 87.38 %. On this basis, cylindrical and wedge-shaped pore models of coal samples were constructed, and molecular dynamics simulations were carried out to investigate the adsorption characteristics of water vapor in these pore models. The results show that the adsorption process of water molecules in coal develops continuously with “initial-water chain-water bridge-water lock”. By summarizing and analyzing the above experimental results, four control mechanisms of coal pore characteristics affecting water vapor adsorption were clarified. These findings are of great significance for studying the movement of water vapor in coal seams and understanding the degree of water confinement caused by hydraulic control measures.

Prediction of the Soil–Water Retention Curve of Loess Using the Pore Data from the Mercury Intrusion Technique

The soil–water characteristic curve (SWCC) is a crucial input parameter for describing the distribution of soil moisture and water movement in various environmental and geotechnical challenges. It is widely recognized that the SWCC is controlled by the soil’s pore structure. Attempts to estimate the SWCC using pore data obtained through the mercury intrusion porosity (MIP) technique have been conducted. However, the performance of MIP estimation remains uncertain and requires further validation with experimental data. In this study, the accuracy of MIP estimation is validated using intact and compacted loess samples prepared at different water contents, specifically dry of optimum (8%), optimum (17%), and wet of optimum (19%). The results reveal that intact and dry of optimum specimens exhibit relatively good pore connectivity, with more point-to-point contacts between particles. Conversely, specimens compacted under optimum and wet of optimum conditions exhibit poor pore connectivity, with more isolated pores, particularly in the wet-of-optimum specimen. The SWCC predictions based on MIP data are accurate for intact and dry-of-optimum compacted specimens, but significant errors occur for the optimum and wet-of-optimum specimens. Prediction accuracy using MIP data is closely linked to the soil’s pore connectivity. Despite a tenuous theoretical basis in the high suction range where adsorption forces dominate, a strong consistency between predictions and measured data across a wide suction range (e.g., 10–104 kPa) instills a high level of confidence in using MIP data to predict the wetting SWCC. The contact angle required for the prediction is suggested as a fitting parameter.

Experimental Study on Spontaneous Imbibition of Coal Samples of Different Ranks Based on the NMR Relaxation Spectrum.

The comprehension of the mechanisms governing spontaneous water imbibition in gas-water systems plays a significant role in the operation of hydraulic fracturing and the development of coalbed methane (CBM). In this study, nuclear magnetic resonance (NMR) techniques were used to investigate the pore structure and fluid behavior of different rank coal samples during spontaneous imbibition. Analyses were conducted on the 1D NMR T2 spectrum, 2D NMR T1-T2 spectrum, and layer division T2 spectra to achieve accurate and detailed information about the internal pore structure of coal and the characteristics of fluid transport during spontaneous imbibition. Low-rank coal exhibits good pore connectivity and favorable pore sorting characteristics, indicating favorable reservoir conditions. High-rank coal has larger pore spaces and highly developed micropores, which are highly beneficial for gas adsorption. However, its poor pore sorting characteristics and connectivity limit the migration and diffusion of fluids within the reservoir. The imbibition capacity follows a specific order of contribution, with small pores (10-50 nm) having the most significant role, followed by micropores (2-10 nm), ultramicropores (r < 2 nm), mesopores (50-1000 nm), macropores (1000-10,000 nm), and microfractures (r ≥ 10,000 nm). Low-rank coal stands out due to the restricted development of ultramicropores and small pores, leading to a different contribution of imbibition capacity compared to other samples, where macropores and microfractures dominate over all pore types. The coal reservoirs with favorable pore sorting characteristics and pore connectivity tend to exhibit a tendency toward rapid saturation and attainment of a prompt stable state during the hydraulic fracturing process. Finally, the mechanism of the late retreat effect of imbibition and the laws governing different coal ranks, pore structures, and fluid transport were discussed. This study offers comprehensive analyses of the mechanism of coal spontaneous imbibition and the characteristic laws of fluid seepage, providing insights into the optimization of CBM recovery and reservoir management.

Characterization of Upper Cretaceous Matulla and Wata clastic reservoirs from October field, Central Gulf of Suez, Egypt

The objective of this study was to integrate petrographic thin sections, SEM, XRD, routine core analysis, gas chromatography, and wireline logs to present a comprehensive petrographic and petrophysical assessment of the shallow marine clastic reservoirs of the Coniacian-Santonian Matulla Formation and upper Turonian Wata Formation from the October field, Central Gulf of Suez Basin. The fine to very fine-grained glauconite-bearing subarkose quartz arenites of the Matulla and Wata reservoirs exhibit good intergranular primary porosity with good pore connectivity. Moderate to slight compaction and grain to grain pressure solution resulted in a slightly inhomogeneous packing of framework grains. Feldspar dissolution contributed to the secondary porosity which improved the reservoir quality, while quartz overgrowth and minor calcite cementation are inferred as porosity destroying diagenetic agents. Pore-filling kaolinite and clay phases also had a negative effect on reservoir storage capacity. Routine core analysis indicated > 20% porosity and up to 412 mD permeability in the meso-megaporous sandstones of both the reservoirs. Permeability anisotropy analysis of Matulla samples indicates the dominance of primary depositional fabric and isotropic pores with minor scattered/connected horizontal pores and vertical pore connectivity. Wireline log-based quantitative petrophysical assessments exhibit low shale volume and higher hydrocarbon saturation (up to 80%) on both the reservoirs, which is also supported by the gas chromatography data confirming the presence of oil in the Matulla, and Wata pay zones based on interpreted gas balance, wetness, and character ratios. The study concludes excellent reservoir properties in the Upper Cretaceous clastic intervals of the October field.

Oil Mobility Evaluation of Fine-Grained Sedimentary Rocks with High Heterogeneity: A Case Study of the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China

The oil mobility in unconventional tight/shale oil reservoirs is complex because of the high heterogeneity in the matrix pore structure and connectivity. Thus, it is difficult to evaluate hydrocarbon exploration potential precisely. In this study, multistep temperature pyrolysis (MTP) Rock-Eval and 1D (dimensional) as well as 2D nuclear magnetic resonance (NMR) techniques were employed to systematically characterize the oil mobility in lacustrine fine-grained sedimentary rocks from the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China. The results show that the Lucaogou Formation fine-grained sedimentary rocks can be subdivided into six types of lithofacies. With the increase of organic matter richness, the content of adsorbed oil increases, whereas the content of movable oil increases first and tends to stabilize (when total organic carbon (TOC) > 4%). This is because when TOC is low, the fine-grained sedimentary rocks need to self-adsorb before oil production; when TOC increases further, the generated oil will break through the absorption limit and charge into the adjacent reservoirs; therefore, the movable oil ceases to increase. Permeability is found to have a greater impact on movable fluid saturation than porosity. Meanwhile, good throat radius and pore connectivity are conducive to oil flow as movable oil is more sensitive to throats rather than pores. Furthermore, a higher content of brittle minerals is not necessarily favorable for oil flow; alternatively, more clay minerals are easy to from cements causing pore blockage, which will essentially hinder oil mobility. Overall, the organic matter content, reservoir pore structure, and rock mineral composition are the main factors affecting tight/shale oil mobility. On the basis of the above research, a conceptual model of oil mobility in different lithofacies’ reservoirs is established. These results have a reference significance for evaluating oil recoverability in fine-grained sedimentary rocks.

Microscopic pore structure and connectivity of lacustrine shale of the Shahejie Formation, Zhanhua Sag, Bohai Bay Basin

As an emerging source of global energy supply, shale reservoirs have extremely low porosity and permeability which are often associated with their highly heterogeneous and poorly connected pores. This is due to peculiar pore structure system and morphology of the shale reservoirs. The focus of this study is to evaluate the pore structure, connectivity and heterogeneities of lacustrine shale reservoirs of the Shahejie Formation within the Bohai Bay Basin using a combination of three methods. These are low temperature gas adsorption experiment (for pore morphology and structure), spontaneous imbibition experiments (for pore connectivity) and nuclear magnetic resonance (NMR) to characterize the structure and fluid saturation of the entire shale sample. The results showed that, high clay content blocked the pore throat and caused significant reduction in connectivity which results in the collapse of pores. However, high content of brittle minerals (e.g. calcite and quartz) promotes the formation of intergranular and intercrystalline pores of inorganic minerals as well as micro-fractures, which favours good pore connectivity in shale. Increase in available space for fluid movement in shales with higher porosity results in a beneficial increase in the mobility of the fluid within the pores. Hence, mineral composition and organic matter content are the two main factors affecting the pore structures within the Zhanhua Sag of the Jiyang Depression in the Bohai Bay Basin.

Integrated petrographical and petrophysical evaluation for reservoir management of the Upper Miocene Qawasim sandstones in West Dikirnis, onshore Nile Delta, Egypt

The Upper Miocene Qawasim Formation is an important hydrocarbon reservoir of the West Dikirnis field, onshore Nile Delta. Here we present a detailed assessment of the Qawasim reservoir by integrating petrographical thin sections, SEM, XRD, wireline logs, and routine core analysis. Eight different lithofacies have been distinguished from cores, which are grouped as four facies associations: massive sandstone (FA-1), massive, gravelly and pebbly sandstone (FA-2), silty laminated sandstone (FA-3) and mudstone (FA-4). FA-4 occurs at the top and bottom of the reservoir interval. The reservoir consists dominantly of massive subfeldspathic arenites (FA-1, FA-2 and FA-3) and exhibits fine to coarse-grained, poorly to moderately sorted and subangular to subrounded texture. The reservoir has high intergranular porosity with good pore connectivity. The feldspar grains are partly leached or near completely dissolved indicating dissolution as a reservoir quality enhancing diagenetic agent. Calcite cementation, authigenic kaolinite precipitation, and minor quartz overgrowth are observed as the porosity destroying processes. Cementation has severe local effects on the reservoir quality of FA-3. The reservoir is dominated by megaporosities (mostly isotropic pore system), exhibits 20–33% porosity,>100 mD horizontal permeability, and a wide range of permeability anisotropy (0.60–24.74). Six hydraulic flow units are identified. Based on the RQI, FZI, and RPI metrics, these flow units are ranked in terms of reservoir quality and vertical permeability baffles are identified. The massive sandstones in the Middle Qawasim flow units are inferred to have superior reservoir quality contributing to 35% of the cumulative storage capacity and ∼75% of the cumulative flow capacity. We employed rock physics models to infer the effects of diagenesis on reservoir petrophysical characteristics. Sediments of constant shale content fall within the constant and contact-cement models and we infer that the velocity-porosity variation in the studied reservoir formation is mainly due to the pore-filling material and less due to the fluid effects. Based on our analyses, we drew inferences on drilling, completion, and optimum reservoir management strategies.

Visualization of CH4/CO2 hydrate dissociation and reformation during multistep depressurization assisted by pore-scale X-ray computed tomography

CH4–CO2 swapping is a promising and safe technique to produce CH4 gas and store CO2 without destabilizing hydrate-bearing sediments. However, inefficient CH4 recovery due to low CO2 diffusion prevents this technique from large-scale application. Multistep depressurization (MD) is therefore performed on CH4/CO2 hydrates after hydrate swapping to improve CO2 diffusion. This work presents pore-scale visualization of CH4/CO2 hydrates during MD by non-destructive X-ray computed tomography (CT) and combines the visual results with mixed hydrate kinetics to study hydrate morphology evolution and fluid migration. Influences of particle sizes (2–5 mm) and L-methionine (3000 ppm) on dissociation parameters were examined at reducing depletion pressures (8.5–59.4 bar) and constant temperatures (0.5–1.3 °C). The results of CT images showed enlargements of hydrate or gas phase with depletion pressures below CH4 hydrate stability pressures, complying with the pressure variations during MD. These variations of hydrate and fluid phases as well as pressure responses were the most obvious for particle size of 3 mm, resulted from good pore connectivity and relatively efficient mass transfer. L-methionine had no direct effect on CH4 production but enhanced CO2 storage, with the highest both CH4 gaseous mole fraction (86.1 mol%) and CO2 storage ratio (88.8%) at depletion pressure of 22.6 bar. This work clarified five-type pressure variations coupled with phase changes, providing firm evidence for hydrate dissociation/reformation and fluid migration that greatly affected hydrate exploitation. These understandings of varying morphologies and compositions of CH4/CO2 hydrates during MD would be applicable to help hydrate energy harvest and carbon emission mitigation.

Petrophysical properties of representative geological rocks encountered in carbon storage and utilization

This study evaluates petrophysical properties (especially porosity, permeability, tortuosity, and diffusivity) of representative geological rocks in the context of injectivity, storage space, and caprock integrity for effective utilization and long-term storage of carbon dioxide. A total of 10 geological rocks were selected as representative storage media for consideration as saline aquifers & depleted oil and gas reservoirs (sandstones and carbonates), basalts, and cap rocks, as well as utilization in organic-rich shale and coal seams. An integrated suite of laboratory tests, including liquid immersion porosimetry, gas expansion porosimetry, grain size distribution, mercury intrusion porosimetry, and gas diffusion, were performed on these various rock samples. The results exhibit a disparity of petrophysical properties among two broad groups of rocks: rocks selected for possible storage of CO2 have porosities of ∼10-25%, permeabilities of ∼10−16-10−13 m2, μm-sized pore-throat size distribution, and mostly good pore connectivity; in contrast, the potential caprocks have porosities of ∼0.5-5%, permeabilities of ∼10−20-10−18 m2, pore throat sizes of <50 nm, and probably poorly connected pore networks. An understanding of the measured facets of pore structure and contribution of fractures is also critical in the context of different testing principles and data interpretation of petrophysical analyses, as well as observational scales in the laboratory and field, and therefore reliable confidence of CO2 storage and utilization performance. Our work further illustrates the controlling influence of grain size distribution and geological processes on pore size distribution and pore connectivity for a wide range of rock types and lithologies, and particularly presents the extent and behavior of CO2 gas diffusion with a custom-designed apparatus for a holistic understanding of various petrophysical attributes of widely different geological rocks.

Diagenetic Facies Controls on Differential Reservoir-Forming Patterns of Mixed Shale Oil Sequences in the Saline Lacustrine Basin

The Permian Lucaogou Formation has developed mixed shale reservoirs, but there are few studies on the diagenetic facies, and the control effect of differential diagenesis on the reservoir capacity of shale oil reservoirs in this area is not clear. Therefore, shale samples of the Lucaogou Formation were systematically selected in this study, and through cast thin sections, field emission scanning electron microscopy, XRD mineral analysis, low-temperature nitrogen adsorption and high-pressure mercury injection experiments, the reservoir capacity of the shale oil reservoirs was evaluated from the perspective of diagenetic evolution. The results show that the shale oil reservoir of the Lucaogou Formation in Jimsar Sag is in the middle diagenetic stage A. The diagenetic evolution sequence is compaction—chlorite cementation—silica cementation—first-stage carbonate cementation—first-stage dissolution of authentic albite—illite/smectite mixed layer cementation—second-stage carbonate cementation—second-stage dissolution. The shale reservoirs are divided into five diagenetic facies: tuffaceous–feldspar dissolution facies, mixed cementation dissolution facies, chlorite thin-membrane facies, carbonate cementation facies and mixed cementation compact facies. Among them, the former two diagenetic facies have strong dissolution and weak cementation and are high-quality diagenetic facies, mainly characterized by large pore volume and good pore connectivity, with relatively low D2 values defined as the fractal dimension of mesopores. On the basis of the above research, three different control models of Lucaogou Formation shale oil reservoirs are proposed, including dissolution to increase pores, chlorite cementation to preserve pores, and strong compaction cementation to reduce pores. The quality of reservoirs developed in this model is successively high, medium, and low. This work can provide guidance for the fine characterization and grading evaluation of mixed shale oil reservoirs in saline lake basins and has important theoretical and practical significance for the prediction of shale oil “sweet spot” distribution.

Electrospun Nanofibrous Membranes: A Versatile Medium for Waterproof and Breathable Application.

Waterproof and breathable membranes that prevent liquid water penetration, while allowing air and moisture transmission, have attracted significant attention for various applications. Electrospun nanofiber materials with adjustable pore structures, easily tunable wettability, and good pore connectivity, have shown significant potential for constructing waterproof and breathable membranes. Herein, a systematic overview of the recent progress in the design, fabrication, and application of waterproof and breathable nanofibrous membranes is provided. The various strategies for fabricating the membranes mainly including one-step electrospinning and post-treatment of nanofibers are given as a starting point for the discussion. The different design concepts and structural characteristics of each type of waterproof and breathable membrane are comprehensively analyzed. Then, some representative applications of the membranes are highlighted, involving personal protection, desalination, medical dressing, and electronics. Finally, the challenges and future perspectives associated with waterproof and breathable nanofibrous membranes are presented.

Negatively Charged Composite Nanofibrous Hydrogel Membranes for High-Performance Protein Adsorption.

Nanofibrous materials are considered as promising candidates for fabricating high-efficiency chromatography media, which are urgently needed in protein pharmaceuticals purification and biological research, yet still face several bottlenecks. Herein, novel negatively charged composite nanofibrous hydrogel membranes (NHMs) are obtained by a facile combination of electrospinning and surface coating modification. The resulting NHMs exhibit controllable morphologies and chemical structures. Benefitting from the combined effect of the stable framework of silicon dioxide (SiO2) nanofiber and the function layer of negatively charged hydrogel, as well as good pore connectivity among nanofibers, NHMs exhibit a high protein adsorption capacity of around 1000 mg g−1, and are superior to the commercial cellulose fibrous adsorbent (Sartobind®) and the reported nanofibrous membranous adsorbents. Moreover, due to their relatively stable physicochemical and mechanical properties, NHMs possess comprehensive adsorption performance, favorable resistance to acid and solvents, good selectivity, and excellent regenerability. The designed NHMs composite adsorbents are expected to supply a new protein chromatography platform for effective protein purification in biopharmaceuticals and biochemical reagents.

Digital rock-based investigation of conductivity mechanism in low-resistivity gas hydrate reservoirs: Insights from the Muli area's gas hydrates

Gas hydrate reservoirs in the Muli area of China are characterized by complex lithology, high hardness, developed micro-fractures, and low porosity-permeability, in which an unusually low-resistivity phenomenon is observed. This phenomenon has led to considerable uncertainty in determining the gas hydrate layers and measuring the gas hydrate saturation. Therefore, it is necessary to understand the underlying factors appropriately to optimize exploration and production. In the present study, digital rock technology was combined with field-scale well-logging data to analyze the conductivity mechanism and identify the causes of the observed low resistivity. The obtained results and sensitivity analysis indicated that the rock porosity was the main controlling factor, and then the formation water salinity, pore structure, micro-fractures, clay components, heavy minerals, and gas hydrate pore-habits were the other significant parameters in the order of high to low significance with the corresponding significance values of 3.64, 2.51, 1.97, 1.72, 1.36, 1.04, and 0.56, respectively. Moreover, wells DK-8, DK11-14, and DK12-13 were taken as examples to analyze the formation mechanism of low-resistivity gas hydrate, and the results showed that the high reservoir porosity, developed micro-pores, high irreducible water saturation and good pore connectivity are the main reasons for the low-resistivity gas hydrate in DK-8; and micro-fractures and the banded distribution of clay are responsible for the low-resistivity gas hydrate in wells DK11-14 and DK12-13, respectively. These findings provide fundamental information for accurate interpretation of the key well-logging data in the study area as well as in similar reservoirs and help improve the exploitation of gas hydrate reservoirs both in the permafrost regions and marine environments.

Programmable, biodegradable composite scaffolds with variable pore morphology for minimal invasive bone repair

Tissue engineered biocompatible scaffolds could mimic the natural bone structure for cell adhesion and proliferation, however, patients suffer from large volume implantation. In this study, a porous composite biocompatible bone scaffold based on shape memory polymer materials (SMP) was developed from poly(ε-caprolactone) (PCL) diol, hexamethylene diisocyanate (HDI) and hydroxyapatite (HA). The prepared shape memory composite scaffold presented good pore connectivity, high porosity, good mechanical and biological properties. Additionally, after programming to a temporary shape, the scaffolds could recover to the initial shape, filling the site of bone defect. Moreover, HA improved the mechanical properties of scaffolds, promoted cell adhesion and influencing the shape recovering speed. During in vitro mineralization, HA could promote the formation and deposition of bone-like hydroxyapatite and accelerate the repair of damaged tissues, no inflammatory problem occurred after the in vivo implantations. These programmable scaffolds could be applied in minimal invasive bone repair.

Mechanism of Methane Adsorption/Desorption in Low-Rank Vitrain and Durain Coal Affected by Pore Structure and Wettability: A Case Study in Dafosi Area, South Ordos Basin, China

Water content and water–coal interface wettability are always the difficult issues of coalbed methane adsorption/desorption. In order to study the effects of the pore structure and wettability of different macro coal components on methane adsorption and desorption, we compared and analyzed the wettability difference between vitrain and durain, and revealed the influence of wettability on methane adsorption and desorption through a pore structure analysis, wettability measurements, an adsorption–desorption experiment and adsorption heat calculations under different conditions, taking the No. 4 coal in Dafosi Coal Mine of the Huanglong coalfield as the research object. The results show that both vitrain and durain are relatively hydrophilic substances. However, vitrain has a low ash content, high volatility, and less oxygen, and the pores are mainly semi-closed pores compared with dark coal. Vitrain also has poor connectivity, poor sorting, a small pore diameter, and a coarser surface, resulting in poor surface wettability. The large specific surface area (SSA) and relatively poor wettability of vitrain leads to more adsorption sites in methane, which makes the adsorption capacity of vitrain greater than that of durain, but the good pore connectivity of durain causes the strong desorption capacity of durain. The isosteric adsorption heat of the adsorption process is greater than that of the desorption process, indicating that there is a desorption hysteresis phenomenon which is essentially due to the lack of energy in desorption. Surfactants change the wettability of the coal surface, and different surfactants have different effects on methane adsorption and desorption. Relatively speaking, the methane desorption of coal samples treated with G502 and 6501 are better. The research results provide scientific reference for the study of gas–water transport in the desorption process of low-rank CBM, and provide evidence for the methane desorption model of vitrain and durain.

Determination of Favorable Lithofacies for Continental Shale Gas: A Case Study of the Shahezi Formation, Changling Fault Depression, Songliao Basin

In order to determine the optimum lithofacies for continental shale, the reservoir characteristics of different lithofacies types were studied based on a series of experiments. The lacustrine organic-rich shale of the Shahezi Formation is divided into siliceous (ORS), argillaceous (ORA), calcareous (ORC), and mixed (ORM) shales. The ORS, ORA, ORC, and ORM shales all carried out comprehensive reservoir comparative analysis. The results showed that the moderate content of clay minerals (45%) can significantly improve porosity, and high and low clay mineral contents are not conducive to the improvement of porosity. The ORM shale tends to have better pore connectivity than the ORS and ORA shales, and the ORC shale has the poorest pore-throat connectivity in micron-size. Internal pores in bitumen and clay shrinkage cracks are the dominant pore type and are well developed in ORS and ORM shales. The two types of pores are less developed in the ORA shale; however, dissolution pores are better developed than those of ORS and ORM shales. Inorganic pores are well-developed in the ORC shale, but organic pores are not. Organic and inorganic pores tend to be better connected in the ORM shale than those of the other three types, which could help improve the gas storage capacity. The ORM shale may have more irregular surfaces and lower liquid/gas surface tension. The higher capillary condensation on pore surfaces is more likely to occur in the ORA shale. The ORS shale offers fewer adsorption sites for CH4 and has lower adsorption capacity. The ORC shale has weak heterogeneity of the pore structure. Therefore, the ORM shale may be the most favorable lithofacies for shale gas enrichment and development, which has high porosity, good pore connectivity, moderate brittleness, and strong gas adsorption and storage capacity, followed by the ORS and ORA shales. The ORC shale is the worst.

Quantitative Characterization of Full-Spectrum Pore Size and Connectivity for Shale with Different Sedimentary Facies from the Dongying Depression, Bohai Bay Basin, East China

Working with shales in the fourth member of Shahejie Formation in the Dongying Depression in Bohai Bay Basin of East China, this study examines the facies classification, petrological characteristics, pore size distribution, and pore connectivity of oil-producing shale. The studied shales could be classified into five sedimentary facies according to a three-step classification criterion that consists of total organic carbon (TOC), sedimentary structure, and mineral composition. Among them, the “low TOC massive siliceous mudstone” and “low TOC layered clayey mudstone” facies have similar distributions from low-pressure N2 physisorption, and the incremental volume within the 3-30 nm pore size range is much higher than the “high TOC laminated clayey marlstone” and “low TOC layered siliceous marlstone” facies. The T 2 spectra of nuclear magnetic resonance tests for the “high TOC laminated clayey marlstone” facies which contains abundant calcite laminae and organic matter-hosted pores commonly show three peaks, with a dominant peak at less than 300 nm in diameter and good pore connectivity. The T 2 spectra of three other facies are both characterized by two peaks, and the main peak of the “low TOC layered siliceous marlstone” and “low TOC layered clayey mudstone” facies has a similar range at 2-500 nm, in contrast with 1-17 nm for the “low TOC massive siliceous mudstone” facies. Pores in these four facies are mainly at nanoscales with predominant pore-throat diameters at less than 50 nm; however, the “high TOC laminated clayey marlstone” facies has the largest peak in the range of &gt;1 μm, possibly because of its interlaminar structure and microcracks. The spontaneous imbibition experiments using two distinct fluids indicated that all of four facies have a much better pore connectivity towards the hydrophilic fluid than these experienced by the hydrophobic fluid.

Quantitative Characterization for Pore Connectivity, Pore Wettability, and Shale Oil Mobility of Terrestrial Shale With Different Lithofacies—A Case Study of the Jurassic Lianggaoshan Formation in the Southeast Sichuan Basin of the Upper Yangtze Region in Southern China

Some major hydrocarbon-bearing basins are rich in shale with terrestrial facies in China, which may provide abundant terrestrial shale oil and gas resources. This work studied the Jurassic Lianggaoshan Formation in the Southeast Sichuan Basin of the upper Yangtze Region. Core samples were chosen for the total organic carbon content and mineral composition analyses to classify shale lithofacies. Afterward, pore connectivity, pore wettability, and shale oil mobility with different lithofacies were characterized by spontaneous imbibition, nuclear resonance, and centrifugation. Conclusions are as follows: the pore connectivity of organic-rich clay shale was mostly between moderate to good with oil-prone wettability and high mobile oil saturation. The organic-rich mixed shale has moderate to good pore connectivity, water-prone wettability, and the highest mobile oil saturation. Organic matter–bearing clay shale has bad to moderate pore connectivity. Meanwhile, its pore wettability covers oil wetting, mixed wetting, oil-prone wetting, and water-prone wetting. Its mobile oil saturation was moderate. Regarding organic matter–bearing mixed shale, the pore connectivity was bad to moderate with mixed-wetting pore wettability and moderate mobile oil saturation.