Pore-Scale Gas Storage Mechanisms, Characteristics, and Influencing Factors in Water-Bearing Shale: Insights from Molecular Dynamics Simulations.

In order to explore the microscopic storage mechanism of shale gas in water-bearing pores and its influencing factors, this article first establishes a molecular dynamics model for methane in different types of adsorbents using molecular dynamics simulation and the grand canonical ensemble Monte Carlo methods. These adsorbents include graphene, organic matter (kerogen), brittle minerals (quartz and albite), carbonate minerals (calcite), and clay minerals (illite, kaolinite, and montmorillonite). Then, by analyzing the molecular storage model and density distribution curves of methane in pores, the storage mechanisms of shale gas are analyzed and elucidated.

End-Member Mixing Model for Methane Carbon Isotope Fractionation During Shale Gas Desorption and Its Application.

Unlike conventional natural gas reservoirs, shale gas development involves systematic changes in methane carbon isotopes that cannot be effectively described by existing isotope fractionation models and mechanisms. Therefore, based on fundamental theories such as Rayleigh fractionation, mass transfer flow, and mass conservation, this study established isotopic fractionation equations for methane in adsorbed and free gas. By considering adsorbed and free gases as two end-members and using an isotope mixing model, a fractionation model for methane carbon isotopes during shale gas desorption was constructed.

Organic Geochemical Characteristics and Organic Matter Enrichment of the Upper Permian Longtan Formation Black Shale in Southern Anhui Province, South China.

Although previous studies have yielded valuable insights into shale gas reservoirs, a comprehensive understanding of the organic geochemical characteristics and organic matter enrichment of marine-continental transitional shale has yet to be achieved. The Longtan Formation transitional shales were extensively deposited in Southern Anhui Province, South China, during the Late Permian. Our analysis of twenty-two rock samples from one core (Gangdi-1 well) and two outcrops (Daoshanchong outcrop and Changqiao outcrop) revealed that the Longtan Formation shale extracts exhibit a wide range of C-C-alkanes and acyclic isoprenoids, with unimodal, bimodal, and multimodal distributions.

Nanoscale Pore Fractal Characteristics of Permian Shale and Its Impact on Methane-Bearing Capacity: A Case Study from Southern North China Basin, Central China.

Fractal dimension is closely related to the nanoscale pore structure of shale, and it also has an important influence on the gas content of shale. To investigate the correlation between the fractal dimension and the methane (CH₄) bearing features of shale, seven Permian shale samples were analyzed with field emission scanning electron microscopy (FE-SEM), low temperature nitrogen (N₂), carbon dioxide (CO₂) and CH₄ adsorption and on-site gas desorption experiments. Based on the N₂ adsorption and desorption data, we proposed a new method to better determine the gas adsorption stage at different relative pressure (/) points in the multilayer adsorption or capillary condensation stage.

Characteristics of three organic matter pore types in the Wufeng-Longmaxi Shale of the Sichuan Basin, Southwest China.

A consensus has been reached through previous studies that organic matter (OM) pores are crucial to porosity in many shale gas reservoirs; however, their origins and types remain controversial. Here, we report the OM pore types hosted in algae, bitumen, graptolite and other fossil fragments in the Wufeng-Longmaxi Formations of the Sichuan Basin, Southwest China. Algae types mainly include multicellular algae, unicellular algae, etc.