Addressing the inherent challenges of low recovery rates and difficulties in shale gas extraction, this study investigates the application potential of CO₂-enhanced shale gas recovery (CO₂-ESGR) coupled with carbon sequestration (CS). Utilizing low-field nuclear magnetic resonance (NMR) technology, we conducted real-time monitoring of methane adsorption and desorption processes within collected shale samples. Through the analysis of T₂ spectra and corresponding peak areas, we achieved quantitative differentiation among adsorbed CH₄, free CH₄ within pore spaces, and free CH₄ within fractures. The results demonstrate that within a pressure range of 0.01–10 MPa, the total methane volume increased progressively from 79.4 to 177.83 cm³/g. Following CO₂ injection, a significant weakening of the short-T₂ signal (representing adsorbed CH₄) was observed, accompanied by a concomitant enhancement of the long-T₂ signal (representing free-phase CH₄). Furthermore, depressurization desorption experiments revealed that CO₂ injection increased the methane desorption rate by approximately 10%, while simultaneously facilitating the long-term, stable sequestration of CO₂ within the shale matrix. These findings not only validate the mechanism of competitive adsorption, whereby CO₂ enhances shale gas recovery, but also highlight the significant carbon sequestration potential of shale reservoirs. Consequently, this research provides a crucial theoretical basis and technical support for advancing both shale gas development and carbon emission reduction strategies.

In shale reservoirs, spontaneous imbibition is an important mechanism of fracturing fluid loss, which has an important impact on enhanced oil recovery and water resource demand. However, spontaneous imbibition behaviors are more complicated to characterize and clarify due to the nanoscale effects of the boundary slip, oil-water interfacial slip, and heterogeneous fluid properties caused by intermolecular interactions. A nanoscale multi-relaxation-time multicomponent and multiphase lattice Boltzmann method was applied to investigate the water imbibition into oil-saturated nanoscale space. The effects of pore size, fluid-surface slip, water film, oil-water interfacial slip, water bridge, and pore structures on the imbibition behaviors in a single nanopore were investigated. Then, the spontaneous imbibition behaviors in nanoporous media based on the pore scale microsimulation parameters obtained from the molecular simulation velocity results were simulated, and the effects of water saturations on imbibition behaviors were discussed. The results show that as the water saturation increases from 0 to 0.1, the imbibition mass in nanoporous media increases because of the oil-water interfacial slip and a completely hydrophilic wall. As water saturation continues to increase, the imbibition mass decreases gradually because the existence of water bridges impedes the water imbibition.