The strength parameters of fault gouge is significant for the fault sealing of underground gas storage. In this paper, direct shear tests are performed for fault gouge composed of different contents of kaolinite(K), montmorillonite(M) and quartz(Q), thus obtaining the shear strength parameters (cohesion c and internal friction angle φ) of various types of fault gouge. The results reveal that: (1) the cohesion of fault gouge is positively correlated with the content of montmorillonite and negatively correlated with the content of quartz. The cohesion of fault gouge specimens with high content of montmorillonite (≥40%) is positively correlated with the content of kaolinite; (2) The internal friction angle of fault gouge is negatively correlated with the content of montmorillonite and positively correlated with the content of kaolinite; (3) The cohesion of fault gouge is positively correlated with the plasticity index I_P, while the internal friction angle is negatively correlated with the plasticity index I_P; (4) The predicted shear strength parameters of fault gouge obtained by statistical methods match well with the experimental results, indicating that statistical method is feasible in predicting the shear strength of fault gouge.

With the progress of geothermal exploration in deep buried geological bodies, high radiogenic geological intrusions have become the hot spot in recent years. However, the assessment of the complex structure, lithology of geological intrusions by the geophysical methods has uncertainty, making it a challenging to accurately predict the thermal structure around the geological intrusions. In southern Québec, Canada, recent studies show that a relative high surface heat flux has been detected in the region enclosed by Montréal, Salaberry-de-Valleyfield and Saint-Jean-sur-Richelieu, around the southwest of the Monteregian Hills, which belong to the Early Cretaceous alkaline and carbonatite intrusions. It is not clear whether these Monteregian intrusions have impacts on the thermal anomaly of the Montréal, Salaberry-de-Valleyfield and Saint-Jean-sur-Richelieu region. The objective of this paper is to numerically investigate the thermal structure in the thermal anomaly region, considering the impact of different Monteregian intrusions. The simplified Monteregian intrusions are embedded into a three-dimensional geological model consisting of the sedimentary formations in the St. Lawrence Lowlands and the simulator Underworld2 is used for the thermal modelling. Simulation results show that the geological intrusions in this region have large impacts on the thermal structure at the local-scale, depending on the radiogenic heat production, thermal conductivity, emplacement depth and size. Temperature in the sedimentary formations may be lower or higher than that of the adjacent geological intrusions, highly depending on the thermal physical characteristics of these intrusions. Furthermore, the complex fault systems also strongly control the thermal distribution in different fault blocks, making the Potsdam Group sandstone located between the Grand-St-Esprit and Notre-Dame-du-Bon-Conseil faults as the potential geothermal reservoir.

A thorough understanding of the microscopic flow process in porous and fractured media is significant for oil and gas development, geothermal energy extraction and subsurface CO₂ storage etc. In CO₂ geological sequestration, the CO₂ is often injected at the supercritical state (scCO₂), which will displace the connate fluids in the pore spaces during the drainage process. However, when CO₂ injection stops, the connate brine or water flows back to displace the scCO₂. Therefore, the configuration of migration paths in a specific reservoir plays a significant role in affecting the connectivity and storage efficiency of scCO₂. In this paper, the two-phase (scCO₂ and water) boundary has been defined using the phase field method, and the COMSOL Multiphysics simulator is applied to study the migration of scCO₂ in porous/fractured media at the pore scale. The geological conditions of Shiqianfeng formation in the CO₂ capture and storage pilot site of the Ordos Basin in China is selected as the engineering background. Before using the actual microscopic geometry based on thin-section of Shiqianfeng sandstone, we get the general understanding on scCO₂ migration in fractured porous media that has the highly simplified configuration with circular particles, considering the impacts of wettability, geometry of formation mineral grains, interfacial tension, injection rates, and fracture geometry. Results show that the CO₂ preferential flow occurs at locations with high CO₂ flow rates and high CO₂ pore pressure. The preferential flow of scCO₂ occurs adjacent to the wall of grains while minimal or little flow takes place through the interior between the grains, considering the grains with irregular shapes. The interfacial tension of porous media plays a significant role in controlling the spatial distribution of the scCO₂. A much lower interfacial tension results in a much thinner scCO₂ flow band with a much higher saturation. The geometry of fractures in porous media increases the complexity of the scCO₂ flow paths at the pore scale.