Gas fracturing technology for enhancing rock permeability is an area with considerable potential for development. However, the complexity and variability of underground conditions mean that a variety of rock physical parameters can affect the outcome of gas fracturing, with temperature being a critical factor that cannot be overlooked. The presence of a temperature field adds further complexity to the process of gas-induced rock fracturing. To explore the effects of temperature fields on gas fracturing technology, this paper employs numerical simulation software to model the extraction of shale gas under different temperature conditions using gas fracturing techniques. The computer simulations monitor variations in the mechanical characteristics of rocks during the process of gas fracturing. This analysis is performed both prior to and following the implementation of a temperature field. The results demonstrate that gas fracturing technology significantly improves rock permeability; temperature has an impact on the effectiveness of gas fracturing, with appropriately high temperatures capable of enhancing the fracturing effect. The temperature distribution plays a crucial role in influencing the results of gas fracturing. When the temperature is low, the fracturing effect is diminished, resulting in a lower efficiency of shale gas extraction. Conversely, when the temperature is high, the fracturing effect is more pronounced, leading to a higher shale gas production efficiency. Optimal temperatures can enhance the efficacy of gas fracturing and consequently boost the efficiency of shale gas extraction. Changes in the parameters of the rock have a substantial impact on the efficiency of gas extraction, and selecting suitable rock parameters can enhance the recovery rate of shale gas. This paper, through numerical simulation, investigates the influence of temperature on gas fracturing technology, with the aim of contributing to its improved application in engineering practices.

Hydrogen and carbon energy reservoirs, critical resources for clean energy development, require precise characterization of their mechanical and fluid flow properties. This study investigates the coupled effects of anisotropic permeability and adsorption-induced deformation on gas extraction efficiency in such reservoirs. A comprehensive numerical model is developed to integrate matrix deformation, crack anisotropy, and adsorption-driven anisotropic swelling within coal reservoirs. The model extends the Langmuir isotherm to incorporate directional adsorption effects and employs a strain-ratio mechanism to quantify permeability evolution induced by non-uniform stresses. Finite element simulations reveal that declining gas pressure near the wellbore intensifies permeability gradients. This finding underscores the necessity of accounting for adsorption-induced volumetric strain to prevent overestimation of coal permeability in traditional models. Anisotropic stress confinement significantly affects gas extraction dynamics, with horizontal permeability (ku) increasing more gradually under depletion compared to vertical permeability (kv). The results highlight pronounced directional variations in extraction rates, with x-direction rates reaching only half of those in the y direction. These findings underscore the importance of addressing permeability anisotropy and adsorption effects to optimize reservoir performance. The study offers valuable insights into the sustainable development of hydrogen and carbon energy resources, providing a theoretical foundation for enhancing gas recovery strategies.

Enhanced geothermal systems (EGS) are a key technology for developing deep geothermal resources, yet they face significant challenges in constructing efficient thermal reservoirs within high-stress, high-strength, and low-permeability crystalline rock formations. Traditional hydraulic fracturing (HF) techniques encounter deep challenges in these environments, including excessively high fracturing pressures, limited fracture network patterns, and the risk of induced seismicity. This paper reviews the multi-scale thermal-mechanical mechanisms, fracture evolution patterns, and control strategies associated with thermal stimulation and permeability enhancement in the modification of deep geothermal reservoirs. Research indicates that thermally induced fracturing triggers intergranular and transgranular cracks at the microscopic scale due to mineral thermal expansion mismatches, which macroscopically manifests as nonlinear degradation of rock strength and modulus. The redistribution of the thermal elastic stress field significantly lowers the breakdown pressure, while matrix thermal contraction increases fracture aperture, leading to an exponential enhancement of permeability following a cubic law. However, the high confining pressure constraints, true triaxial stress anisotropy, and thermal short-circuiting risks present substantial suppression and challenges to the effectiveness of thermal stimulation in deep in situ environments. Different fracturing media, such as water, liquid nitrogen (LN₂), and supercritical CO₂, exhibit varying advantages in thermal stimulation efficiency due to their unique thermal-flow characteristics. Future research should focus on the thermal-mechanical coupling mechanisms under true triaxial stress conditions, and develop intelligent control strategies for permeability enhancement and thermal short-circuiting risk mitigation. This study synthesizes existing analyses and proposes potential engineering strategies for stimulating deep EGS reservoirs, offering significant strategic value for the development of geothermal energy as a baseload renewable resource.

As a new type of underground water conservancy project, underground reservoirs in coal mines play a crucial role in protecting and utilizing water resources during mining operations. The safety and reliability of the dam body are key to this technology. Focusing on the basic situation of the Shendong 2–2 coal seam coal mine underground reservoir, this paper uses mechanical analysis, mechanical testing and other methods. From the perspective of the dam body stability under the combined effects of seismic activity and water immersion, this study analyzes the changes in the stability of the dam body during reservoir operation. It focuses on the dynamic impacts of earthquakes and mining-induced tremors, along with the long-term effects of water immersion. By comprehensively analyzing the changes in stress, displacement, and other parameters when the combined dam body (coal pillar + concrete) fails, the research identifies the locations and causes of damage to the dam body under the impact of earthquakes. It also proposes precursor information and characteristics of dam body instability under long-term water immersion and dynamic load effects. The results indicate that under water storage conditions (horizontal stress combined with water immersion), the coal pillar undergoes displacement and eventually becomes unstable, facturing upon reaching its limit strength. Water immersion reduces the mechanical strength of the coal pillar. For a coal pillar 15 m thick, the maximum water storage height is 50 m. It is recommended that displacement changes be used as precursor information for dam body monitoring and early warning during the actual water storage process. The “coal pillar–concrete” combined dam body can resist earthquakes of magnitude 10 and above (1.2 g). During earthquakes, the bottom and middle parts of the dam are the main locations of stress concentration, with the stress change pattern being bottom > middle > top. Due to the difference in material properties between the concrete and coal pillar dam bodies, the difference in acceleration between the two during earthquakes is about 1.14 times, causing the bottom of the coal pillar to be the first to break. Additionally, the stress peak on the submerged side body during an earthquake is about 10% higher than that on the front. This research is important for the stability analysis and monitoring and early warning of underground reservoirs in coal mines and provides a reference for the stability of other underground projects.