Heterogeneous Pore Research Articles

Effects of Pore Water on the Heterogeneity in Nanopore Structures of Deep Marine Shales: A Multifractal Study on As-Received Shale Samples from the Southern Sichuan Basin, China

Shale strata generally contain a certain amount of pore water that accompanies the whole diagenetic and thermal evolution processes of shales. The distribution and occurrence characteristics of pore water significantly influence the nanopore structures of shales, which subsequently affects the accumulation and production of shale oil and gas resources. Based on a set of fresh Wufeng–Longmaxi (WL) shale samples from the deep marine strata in the southern Sichuan Basin, this study investigated the effects of pore water on the pore heterogeneity of shales by a multifractal method. The results show that (1) the deep WL shales have low pore water content (CPW) and water saturation (SEW), with average values of 7.47 mg/g and 35.21%, respectively, and the CPW and SEW of the shales are mainly controlled by clay mineral content. (2) Under dried conditions, the pore heterogeneity of high-probability measure areas has negative relationships with the clay mineral content and pore volumes with pore widths of 4–10 nm, and the pore connectivity is mainly controlled by clay mineral content. Under as-received conditions, however, the pore heterogeneity of low-probability measure areas and pore connectivity have positive relationships with clay mineral content and pore volumes with pore widths less than 4 nm. (3) Under as-received conditions, the pore water mainly occupies the nanopore with pore widths less than 4 nm and reduces the effective pore spaces and connectivity, which reduces the pore heterogeneity of high-probability measure areas and enhances the pore heterogeneity of low-probability measure areas.

A Facile Strategy for the Fabrication of Cell-laden Porous Alginate Hydrogels Based on Two-phase Aqueous Emulsions.

Porous alginate hydrogels possess many advantages as cell carriers. However, current pore generation methods require either complex or harsh fabrication processes, toxic components, or extra purification steps, limiting the feasibility and affecting the cellular survival and function. In this study, a simple and cell-friendly approach to generate highly porous cell-laden alginate hydrogels based on two-phase aqueous emulsions is reported. The pre-gel solutions, which contain two immiscible aqueous phases of alginate and caseinate, are crosslinked by calcium ions. The porous structure of the hydrogel construct is formed by subsequently removing the caseinate phase from the ion-crosslinked alginate hydrogel. Those porous alginate hydrogels possess heterogeneous pores around 100 μm and interconnected paths. Human white adipose progenitors (WAPs) encapsulated in these hydrogels self-organize into spheroids and show enhanced viability, proliferation, and adipogenic differentiation, compared to non-porous constructs. As a proof of concept, this porous alginate hydrogel platform is employed to prepare core-shell spheres for coculture of WAPs and colon cancer cells, with WAP clusters distributed around cancer cell aggregates, to investigate cellular crosstalk. This efficacious approach is believed to provide a robust and versatile platform for engineering porous-structured alginate hydrogels for applications as cell carriers and in disease modeling.

Parameters Variation and Flow Characteristics When CO2 Displacing Brine in Four Micromodels Simulating Carbon Sequestration in Saline Aquifers

Two-phase flow of CO2/brine in porous media is critical to the capacity and safety of carbon sequestration into the brine aquifer. In order to provide valuable information and important theoretical basis for site selection and CO2 injection, the microscopic visualization technology was employed in this study to conduct displacement experiments of CO2/brine at the pore scale. Four micromodels with different sizes and structures, five injection rates of CO2, and six salinities of brine were used to study the effects of micromodel’s structure and displacement pattern on two-phase flow. Several parameters including the differential pressure, contact angle, permeability, velocity field, and force field were obtained by experimental measurement, image post-processing, and theoretical analysis, and then, these parameters’ variation was investigated. Phenomena such as thin film, corner flow, and Haines jump were also found during the displacement. Although brine could be completely displaced by CO2 in the capillary duct, the backflow of the wetting phase would occur at a low injection rate. Phenomena different from the theoretical analysis also occurred in pore doublet models: some brine was residual in the homogeneous pore doublet model at a low injection rate, while the heterogeneous pore doublet model was fully occupied by CO2 at a high injection rate. These phenomena are very useful for two-phase flow, and multiple factors need to be comprehensively considered to determine the operating conditions of CO2 storage into the brine aquifer.

Microscopic Pore Structures and Their Controlling Factors of the Lower Carboniferous Luzhai Shale in Guizhong Depression, China

Microscopic pore structures are of great significance in evaluating shale gas reservoirs and understanding the occurrence state of shale gas. Integrating geochemical analysis, X-ray diffraction (XRD), low-temperature N2 adsorption (LTNA), mercury injection pressure (MIP), small-angle X-ray scattering (SAXS), and field emission scanning electron microscope (FE-SEM), this work systematically characterized microscopic pore structures and then discussed their controlling factors, for the Lower Carboniferous Luzhai (C1lz) shale in Guizhong Depression. The results show that pores in the Luzhai shale are generally shaped by ink bottles, parallel plates, and slits, which are characterized by a larger pore throat ratio, lower efficiency of mercury withdrawal, and poor connectivity. Micropores (<2 nm) and mesopores (2 nm-50 nm) provide the primary specific surface area (SSA) of shale reservoirs, dominantly controlled by the contents of TOC and clay minerals, whereas pore volume is mainly contributed from mesopores, which is positively correlated to quartz content. The fractal dimension (2.94) of macropores is higher than that (2.65) of mesopores, corresponding more complicated and heterogeneous pore structure. With increasing pore size, the correlation between TOC and fractal dimension of macropores weakens. The unconnected pores in mesoscopic range are more complex than connected pores, primarily resulting from morphology and deformation of clay minerals.

Pore structure and fractal characteristics of tight sandstone in meandering stream facies: a case study of the J2s2 member in the central Sichuan Basin, China

Based on porosity and permeability tests, high-pressure mercury injection (HPMI), nuclear magnetic resonance (NMR) and centrifugal experiments, this study comprehensively analyzed the quality, pore structure and fractal characteristics of tight sandstone reservoir in meandering stream facies. The purpose is to reveal the relationship between physical properties, geometry and topological parameters of pores, fluid mobility and heterogeneity of pore system of tight sandstone reservoirs in meandering stream facies. The results show that the second member of the Middle Jurassic Shaximiao Formation (J2S2) in the central Sichuan Basin has developed tight sandstone reservoir of meandering fluvial facies, the pore radius of type I reservoir (K>0.3 mD) is mainly distributed at 0.01 μm∼2 μm, the tortuosity ranges between 2.571 and 2.869, and the average movable fluid saturation is 70.12%. The pore radius of type II reservoir (0.08mD<K<0.3 mD) is mainly 0.003 μm∼1 μm, the tortuosity ranges between 2.401 and 3.224, the average movable fluid saturation is 57.59%. The pore radius of type III reservoir (K<0.08 mD) is mainly 0.001 μm∼0.4 μm, the tortuosity ranges between 0.905 and 2.195, and the average movable fluid saturation is 13.46%. Capillary-Paraachor point (CP point) and T2 cut-off value (T2cutoff) are used to divide the fractal interval of capillary pressure curve and T2 spectrum. The fractal dimension Dh2 of small pores calculated by HPMI through 3D capillary tube model, the fractal dimension Dn1 of large pores and Dn2 of small pores calculated by NMR through wetting phase model can effectively characterize the heterogeneity of reservoir pores. Among them, Dn1 has a strong negative correlation with porosity, permeability, pore radius and movable fluid saturation, indicating that the reservoir capacity, seepage capacity and pore size are mainly controlled by large pores, therefore, Dn1 can be used as an effective reservoir evaluation parameter.

Micro-nano scale pore structure and fractal dimension of ultra-high performance cementitious composites modified with nanofillers

The development of ultra-high performance cementitious composite (UHPCC) represents a significant advancement in the field of concrete science and technology, but insufficient hydration and high autogenous shrinkage relatively increase the pores inside UHPCC, in turn, affecting the macro-performance of UHPCC. This paper, initially, optimized the pore structure of UHPCC using different types and dimensions of nanofillers. Subsequently, the pore structure characteristics of nano-modified UHPCC were investigated by the mercury intrusion porosimeter method and fractal theory. Finally, the fluid permeability of nano-modified UHPCC was estimated by applying the Katz-Thompson equation. Experimental results showed that all incorporated nanofillers can refine the pore structure of UHPCC, but nanofillers with different types and dimensions have various effects on the pore structure of UHPCC. Specifically, CNTs, especially the thin-short one, can significantly reduce the porosity of UHPCC, whereas nanoparticles, especially nano-SiO2, are more conducive to refine the pore size. Among all nanofillers, nano-SiO2 has the most obvious effect on pore structure, reducing the porosity, specific pore volume and most probable pore radius of UHPCC by 31.9%, 35.1% and 40.9%, respectively. Additionally, the pore size distribution of nano-modified UHPCC ranges from 10−1nm–105nm, and the gel pores and fine capillary pores in the range of 3–50 nm account for more than 70% of the total pore content, confirming nanofillers incorporation can effectively weaken pore connectivity and induce pore distribution to concentrate at nanoscale. Fractal results indicated the provision of nanofillers reduces the structural heterogeneity of gel pores and fine capillary pores, and induces homogenization and densification of UHPCC matrix, in turn, decreasing the UHPCC fluid permeability by 15.7%–79.2%.

Porosity distribution in the Devonian Antrim Shale: Controlling factors and implications for gas sorption

Unconventional reservoirs, such as oil and gas shales, are characterized by diverse and heterogeneous pore systems, and their detailed knowledge is critical for understanding fluid storage and transport mechanisms. The Devonian Antrim Shale in the Michigan Basin is an unconventional, primarily biogenic gas accumulation with a technical recoverable resource of 19.9 Tcf. While its general formation properties are known, the details of porosity distribution and pore morphology are lacking. This study provides a comprehensive description of the total porosity, pore size distribution, pore morphology and mineral associations for various members of the Antrim Shale sampled at three locations across the basin, and then investigates the factors controlling porosity distribution and the implications for gas sorption. Results indicate that the black-shale members, the Lachine and Norwood, are characterized by a lower porosity (0.1–2%) compared to the organic-lean members, the Paxton and Upper Antrim (2–7% porosity). Total porosity tends to decrease with the increase in organic content in the Antrim Shale as organic matter, in particular solid bitumen, occludes available pore space between mineral grains in the organic-rich black shale members. Organic matter displays little to no porosity of its own at the SEM resolution, but gas adsorption measurements indicate the presence of micropores (<2 nm), whose amount correlates positively to the total organic content. The Norwood member (TOC values up to 25%) is characterized by the largest share of micropores (up to 37% of the total porosity volume), while the organic-lean Paxton Member (TOC < 6%) has the least amount of microporosity (1–6%). Only the Lachine Member and select Upper Member samples showed larger organic matter pores, visible in the SEM images (∼50–100 nm). Mesopores (2–50 nm) are the dominant pore size group in the Antrim Shale, forming 45% to 76% of the pore space, and most of the pores are interparticle and intraparticle pores in and around clays, quartz, feldspar and pyrite grains. No single mineral component influences the total porosity distribution, but clay content exhibits a weak positive correlation to the meso-macro porosity. As microporosity is known to contribute the most to gas adsorption capacity of unconventional reservoirs, TOC appears to be most important factor controlling both CH4 and CO2 storage potential of the Antrim Shale. The Norwood Member, characterized by the highest TOC and microporosity volume as well as surface area of the micropores, is predicted to have the highest gas adsorption capacity but direct sorption measurements will be needed to confirm that. This study highlights some important differences with previous observations about porosity relationship to organic and mineral components of shale reservoirs, and expands the understanding of shale pore systems in the low-maturity range of organic-rich shales.

Facile Synthesis of Metallosalphen-Based 2D Conductive Metal-Organic Frameworks for NO2 Sensing: Metal Coordination Induced Planarization.

As an emerging class of promising porous materials, the development of two-dimensional conductive metal organic frameworks (2D c-MOFs) is hampered by the few categories and tedious synthesis of the specific ligands. Herein, we developed a nonplanar hexahydroxyl-functionalized Salphen ligand (6OH-Salphen) through a facile two-step synthesis, which was further applied to construct layered 2D c-MOFs through in situ one pot synthesis based on the synergistic metal binding effect of the N2 O2 pocket of Salphen. Interestingly, the C2v -symmetry of ligand endows Cu-Salphen-MOF with periodically heterogeneous pore structures. Benefitting from the higher metal density and shorter in-plane metal-metal distance, Cu-Salphen-MOF showcased excellent NO2 sensing performance with good sensitivity, selectivity and reversibility. The current work opens up a new avenue to construct 2D c-MOF directly from nonplanar ligands, which greatly simplifies the synthesis and provides new possibilities for preparing different topological 2D c-MOF based functional materials.

Facile Synthesis of Metallosalphen‐Based 2D Conductive Metal‐Organic Frameworks for NO2 Sensing: Metal Coordination Induced Planarization

AbstractAs an emerging class of promising porous materials, the development of two‐dimensional conductive metal organic frameworks (2D c‐MOFs) is hampered by the few categories and tedious synthesis of the specific ligands. Herein, we developed a nonplanar hexahydroxyl‐functionalized Salphen ligand (6OH‐Salphen) through a facile two‐step synthesis, which was further applied to construct layered 2D c‐MOFs through in situ one pot synthesis based on the synergistic metal binding effect of the N2O2 pocket of Salphen. Interestingly, the C2v‐symmetry of ligand endows Cu‐Salphen‐MOF with periodically heterogeneous pore structures. Benefitting from the higher metal density and shorter in‐plane metal‐metal distance, Cu‐Salphen‐MOF showcased excellent NO2 sensing performance with good sensitivity, selectivity and reversibility. The current work opens up a new avenue to construct 2D c‐MOF directly from nonplanar ligands, which greatly simplifies the synthesis and provides new possibilities for preparing different topological 2D c‐MOF based functional materials.

Prediction of lithology in lacustrine carbonates using well logs: The Cretaceous Barra Velha Formation in Santos Basin, offshore Brazil

Abundant hydrocarbons have been produced from the pre‐salt lacustrine carbonates of the Cretaceous Barra Velha Formation in the Santos Basin of offshore Brazil. The highly heterogeneous lithology and pore systems make it difficult to predict the reservoir quality via petrophysical well logs. Core description, computed tomography (CT) scanning, thin sections and wireline well logs are utilized to characterize the lithology, pore spaces are reservoir quality of the Cretaceous Barra Velha Formation pre‐salt lacustrine carbonates in the Santos Basin. The results show that the lithology mainly includes shrubstone, grainstone, laminated micrite and massive micrite. The pore systems are dominated by secondary pores, such as intergranular pores, dissolution pores and intercrystalline pores as well as modified primary pores. Geological well logs (conventional well logs, electrical and sonic image logs and nuclear magnetic resonance [NMR] logs) are integrated to build the predictable models of the carbonate reservoirs. The shrubstone, which is dominated by intergranular pores, has the highest reservoir quality, which can be derived from NMR logs. Grainstone contains both primary intergranular pores and abundant secondary dissolution pores. The laminated and massive micrite contain only micropores and therefore have the lowest reservoir quality. Lastly, conventional well logs integrated with electrical and sonic image logs are utilized to predict the distribution of lithology and reservoir quality in single wells, and the results are testified by the NMR log data. The shrubstone and grainstone are future exploration targets of the Cretaceous Barra Velha Formation in the Santos Basin. The results are hoped to give insights into the petrophysical behaviours of various lithologies, and provide theoretical and technical guidance for reservoir evaluation and prediction.

Pore throat structure heterogeneity and its effect on gas-phase seepage capacity in tight sandstone reservoirs: A case study from the Triassic Yanchang Formation, Ordos Basin

The microscopic heterogeneity of pore-throat structures in tight sandstone is a crucial parameter for understanding the transport mechanism of fluid flow. In this work, we firstly developed the new procedure to characterize the pore size distribution (PSD) and throat size distribution (TSD) by combining the nuclear magnetic resonance (NMR), cast thin section (CTS), and constant-rate mercury injection (CRMI) tests, and used the permeability estimated model to verify the full-scale PSD and TSD. Then, we respectively analyzed the fractal feature of the pore and throat, and characterized the heterogeneity of pores and throats. Finally, we elaborated the effect of the pore and throat heterogeneity on the gas-phase seepage capacity base on the analysis of the simple capillary tube model and gas-flooding experiment. The results showed that (1) The PSD and TSD of the tight sandstone sample ranged from 0.01 to 10 μm and from 0.1 to 57 μm, respectively, mainly contributed by the micropores and mesopores. Meanwhile, the permeability estimated by the PSD and TSD was consistent with the experimental permeability, and relative error was lower than 8%. (2) The PSD and TSD exhibited multifractal characteristics, and singularity strength range, Δα, could be used as the indicator for characterizing the heterogeneity of pore and throat. Furthermore, the throat of the sample showed stronger heterogeneity than that the pore. (3) The throats played an important role for the fluid transport in the tight sandstone, and the effect of the throat heterogeneity on the gas-phase seepage capacity was different under the lower and higher injection pressure. The macropores and micropores maybe respectively become the preferential migration pathways at the lower and higher injection pressure. In the end, the identification plate was established in our paper, and could be described the relationship among the throat heterogeneity, injection pressure, permeability and flow path of the gas phase in the tight sandstone.

Quantitative characterization of shale pore connectivity and controlling factors using spontaneous imbibition combined with nuclear magnetic resonance T2 and T1-T2

Shale oil can be extracted from shale by using interconnected pore networks. The migration of hydrocarbon molecules within the shale is controlled by pore connectivity. However, assessing the pore connectivity of shale oil reservoirs is uncommon. To characterize pore connectivity and clarify its controlling factors, this study used spontaneous imbibition (SI) combined with nuclear magnetic resonance (NMR) T2 and T1-T2 technologies on shale oil reservoirs selected from the Shahejie Formation in the Dongying Sag, Bohai Bay Basin. According to the findings, the SI processes of shales include fast-rising, slow-rising, and stable stages. The fast-rising stage denotes pore connectivity. The shales studied have poor connectivity, with lower imbibition slopes and connected porosity ratios, but large effective tortuosity. During the SI process, micropores have the highest imbibition saturation, followed by mesopores and macropores. Furthermore, n-dodecane ingested into micropores appears primarily as adsorbed, whereas n-dodecane appears primarily as free states in mesopores and macropores during the SI process. The pore connectivity of the shales under study is primarily controlled by inorganic minerals. Quartz and feldspar develop large and regular pores, resulting in better pore connectivity, whereas clay minerals and calcite with plenty of complex intragranular pores do not. Organic matter negatively influences pore connectivity because the dissolution of calcite by organic acid produced during hydrocarbon generation leads to a more complex and heterogeneous pore structure. This study sheds light on the pore connectivity and controlling factors of the shale oil reservoir and aids in the understanding of shale oil mobility.

Performance improvement of lateral flow assay using heterogeneous nitrocellulose membrane with nonuniform pore size

Lateral flow assay (LFA) has found widespread applications in point-of-care diagnostics over the past decades. Its detection sensitivity is dependent on the properties of paper itself (e.g., porous microstructure of nitrocellulose membrane), however, the effect remains unknown. Existing mathematical models for LFA have not been proved to predict the variation trends of detection performance with different specifications of nitrocellulose membrane. To address this, we developed a mathematical model coupling the macroscopic capillary flow and the binding reaction on the internal pore surface to illustrate the complex interaction among the convection, diffusion, and binding reaction with different nitrocellulose membranes. The model was experimentally validated by implementing nucleic acid detection on LFA. The simulated results suggest that due to the trade-off between the reagent transport and the reactive surface area, there is an optimal average pore size of the nitrocellulose membrane to achieve the highest detection sensitivity. Additionally, a heterogeneous pore distribution design (i.e., smaller pore diameter at the test line region and larger pore diameter for the rest region) of the nitrocellulose membrane was proposed to provide a faster detection with improved sensitivity. The numerical model would be a practical tool for the material selection and optimization of LFA.

Kaempferol molecularly imprinted polymers: preparation, characterization and application to the separation of kaempferol from ginkgo leaves

AbstractIn this work, kaempferol molecularly imprinted polymers (MIPs) were screened in detail and were applied to the separation of kaempferol from real complex systems. Kaempferol‐MIPs with high affinity and selectivity for kaempferol could be prepared successfully by using kaempferol as the template molecule, 4‐vinylpyridine as the functional monomer, ethylene glycol dimethacrylate or divinylbenzene as the crosslinker, acetone or acetonitrile as the solvent. Scanning electron microscopy observation and Brunauer–Emmett–Teller measurement showed that the prepared MIPs had a heterogeneous pore structure and large specific surface area. Static and dynamic adsorption experiments and solid‐phase extraction application were performed to evaluate the performance of the prepared MIPs. Only the MIPs with both higher distribution coefficient and higher imprinting factor in the dynamic experiments had better ability to retain kaempferol. Using the screened MIPs as solid‐phase extraction sorbents, kaempferol and quercetin were extracted directly from the crude ginkgo leaves hydrolysate with high recovery and purity. Control experiments also showed that the screened MIPs were superior to commercially available adsorbents in terms of the separation of kaempferol from crude extracts. © 2023 Society of Industrial Chemistry.

Underground hydrogen storage in reservoirs: pore-scale mechanisms and optimization of storage capacity and efficiency

Underground Hydrogen Storage in Reservoirs (UHSR) is promising for long-term and large-scale renewable energy storage, yet improvements in capacity and efficiency are still highly demanded, which requires a deep understanding of the pore-scale mechanisms. Here, we investigate UHSR using micromodels and discover three pore-scale mechanisms, namely the preferential-to-uniform flow transformation, floating flow, and dead-end pore invasion. Preferential flows ensure the base storage capacity and the early transformation to uniform flows promotes the storage efficiency. Floating flow not only enhances the flow transformation but also increases the storage capacity via its facilitation for dead-end pore invasion. We also provide pore-scale mechanism-based elucidation for the effects of pore heterogeneity, injection flux, and oil/brine distribution on storage capacity and efficiency. Injection flux affects the preferential and floating flows to regulate the rate of base storage and determine whether controlling the flow profile or breaking through the outlet via inertia induced preferential flow. Pore heterogeneity affects the proportion of dynamic dead-end pores and possibility of breaking through via capillary induced preferential flow. In comparison with brine saturated condition, the oil saturated condition is unfavorable of floating flow and dead-end invasion. We propose that brine saturated initial condition with high injection flux and median pore heterogeneity are optimal for both UHSR capacity and efficiency from our micromodel study. We further optimize the capacity from 50 % to 95 % and the efficiency from 7.4 × 10-2 kg/(m3·s) to 2.1 × 10-1 kg/(m3·s) according to revealed mechanisms and influencing factors. From the microscale perspective, this work brings critical insights for enhancing and broadening the application of UHSR engineering practice.

Method Selection for Analyzing the Mesopore Structure of Shale—Using a Combination of Multifractal Theory and Low-Pressure Gas Adsorption

Nitrogen adsorption experiments have been extensively applied to shale pore structure research and evaluation. The pore structure can be quantitatively characterized in accordance with the nitrogen adsorption–desorption isotherm using various calculation models, whereas the results obtained using different models can more effectively indicate the pore characteristics of shale remains unclear. Further, there has not been any unified process in the optimization of calculation models for pore size distribution (PSD). In this study, the Barret–Joyner–Halenda adsorption (BJH-AD) and BJH desorption (BJH-DE) models were used with Longmaxi Formation shale as an example. Subsequently, the density functional theory (DFT) calculations were conducted on different shale lithofacies samples. Next, the pore structure parameters and heterogeneity obtained using different models were compared, and the consistency parameters of different models were obtained in accordance with Cronbach’s alpha. The results indicated that the pore structure parameters obtained using the BJH-AD model were underestimated since the macroscopic thermodynamic theory was not applicable to this study. The DFT model showed multiple peaks in the range of 1–10 nm, whereas the BJH-DE model had a significant artificial peak in the range of 3.8 nm due to the tensile strength effect, thus suggesting that the DFT model is more capable of characterizing the pores with a pore size 10 nm lower than the BJH model. The PSD curves generated using the three models exhibited multifractal characteristics, whereas the results of the heterogeneity achieved using different models were different. Moreover, the consistency of the results of different models can be studied in depth by combining Cronbach’s alpha with various heterogeneity parameters. The DFT model exhibited high consistency in pore structure parameters and pore heterogeneity, thus suggesting that the DFT method of N2 is the optimal physical adsorption data analysis method in the shale mesoporous range. Accordingly, the nitrogen adsorption curve, the hysteresis loop shape, multifractal parameters, and Cronbach’s alpha were integrated to generate a working flow chart of the nitrogen adsorption model for N2-adsorption-model optimization.

Characteristics and Influencing Factors of Multi-Scale Pore Structure Heterogeneity of Lacustrine Shale in the Gaoyou Sag, Eastern China

The success of shale oil exploration and production is highly dependent on the heterogeneous nature of the reservoir pore structure. Despite this, there remains limited research on the heterogeneity characteristics of pores at different scales in lacustrine shale oil reservoirs and the factors that impact them. This study aims to quantitatively characterize the multi-scale pore heterogeneity differences of the lacustrine shale found in the Funing Formation in Gaoyou Sag. Additionally, the study seeks to clarify the impact of the total organic carbon (TOC) and lithofacies type on pore structure heterogeneity. To achieve this, nitrogen adsorption, scanning electronic microscope (SEM), mercury intrusion porosimetry (MIP), and other experimental means were adopted in combination with the fractal dimension model of FHH and capillary. The results show that the predominant lithofacies of the Funing Formation shale samples are mixed shale (MS) and siliceous shale (SS), with a limited presence of calcareous shale (CS). The micro-pores of lacustrine shale are dominated by inorganic mineral pores and fewer organic pores. Intragranular pores and clay mineral pores are two types of inorganic mineral pores that are widely found. Small pores (pore diameter &lt; 50 nm) make up 89% of the pore volume (PV) and 99% of the specific surface area (SSA). The fractal dimensions D1, D2, and D3 were calculated to characterize the roughness of the pore surface, the structural complexity of small pores, and the structural complexity of large pores (pore diameter &gt; 50 nm), respectively. The increase in the total organic carbon (TOC) resulted in a decrease in the D1, D2, PV, and SSA, while connectivity showed a slight improvement. The fractal dimension of shale across all lithofacies followed the pattern: D3 &gt; D2 &gt; D1. The pore structure is more complex than the pore surface, and the large pores showed a greater heterogeneity than the small pores. Among the three lithofacies, CS had the largest PV, SSA, D1, and D2, indicating the development of a more complex pore structure network. This expands the space required for shale oil occurrence. However, the connectivity of the CS lithofacies is the lowest among the three, which hinders shale oil production. Although the PV of SS is slightly lower than that of CS, its average pore diameter (AVE PD) and connectivity are significantly advantageous, making SS an ideal shale reservoir. This study provides an important reference for the reservoir evaluation required to better develop lacustrine shale oil around the world.

3D confocal imaging methodology optimized for pore space characterization of carbonates

Pore space characterization of carbonate materials is of fundamental importance to a wide range of earth science and engineering applications. In this study, we show how confocal microscopy can be used as a reliable tool to visualize and quantify the heterogeneous pore space in carbonate materials. In confocal imagery, the quality of pore space images is controlled by various factors including the choice of fluorophore, objective lens, and medium of imaging. Our experiments demonstrated that there is no “fit-for-all” dye. The red dye provides more depth of investigation, while the blue dye can capture large pores more efficiently. Our investigation indicated that quantitative pore space description from confocal images can be significantly influenced by imaging artifacts associated with imaging the heterogeneous and complex pore space in carbonates. By applying image deconvolution, we mitigated the confocal imaging artifacts (e.g., spherical aberration, and resolution deviation), and extracted a more reliable 3D pore-network model of the carbonate sample. We employed our optimized confocal imaging protocol to visualize and quantify macro- and micropores, and more importantly their interconnectivity within an Indiana limestone (IL) sample. The computed pore-throat size distribution (PSD) from the 3D confocal images was able to capture the inherent bimodal distribution of IL.

Influence of coalification on pore structure evolution in middle-ranked coals

The influence of coalification on coal structure evolution in middle ranked coals is significant for physical assessment of coalbed methane (CBM) reservoirs, which provides insights on the intrinsic connection between coalification jump and pore heterogeneity. A total of 26 middle-ranked coals were samples covering Liupanshui Coalfield in Guizhou Province, Anhe Coalfield in Henan Province, Huaibei Coalfield in Anhui Province, Sanjiang Basin in Heilongjiang Province, Ordos Basin in Shaanxi Province and Qinshui Basin in Shanxi Province. Based on a series of experiments including vitrinite reflectance, coal maceral identification, nitrogen adsorption and the pore fractal method, the inner link between physical property parameters of coal reservoirs and coal rank was revealed. The results show that the coal maceral in middle rank coals is dominated by vitrinite and inertinite and two types of adsorption pores are divided according to the nitrogen adsorption/desorption curves along with pore size distribution. The specific surface area is positively correlated with total pore volume, micropore volume and negatively correlated with averaged pore size and transitional pore volume. The coal samples with low average pore sizes have relatively high total pore volume, specific surface area and micropore volume per unit nm. With the increase of coal rank, the fluctuating points of micropore and transitional pore volume correspond to 1.16%–1.19%, 1.41%–1.43% and 1.86%–1.91% of Ro, max, respectively. The boundary of Ro, maxcorresponding to the second coalification jump can be more specifically defined as 1.16%–1.19% from the established nominal range of 1.1%–1.3%. The pore fractal dimension DNA1and DNA2increase with increasing specific surface area. Furthermore, the DNA2has a negative correlation with micropore volume and averaged pore size, indicating that the coal with smaller average pore diameter and lower micropore content has a more complex pore structure.

Force prediction and analysis in surgical sawing of composite bone involving multi-tooth reciprocating and heterogeneous pore model

Force prediction and analysis in surgical sawing of composite bone involving multi-tooth reciprocating and heterogeneous pore model