Due to the unique structural characteristics of hydrate, it has a potential application value in coal and gas outburst prevention in coal mines. Given the complexity of subsurface environments, it is essential to investigate the hydrate formation kinetics under varied initial conditions, as well as the subsequent impacts of hydrate formation on coal seam properties. This research mainly focuses on the hydrate formation process in coal samples with different coalification degrees under different initial pressure and water saturation conditions by using the designed hydrate formation system. The results show that gas consumption and hydrate saturation can be greatly enhanced by increasing the initial water saturation and pressure, which is favorable to reduce the coal seam gas pressure and improve the coal seam peak strength. The calculation results suggest that hydrate formation at varying saturation reduces the gas pressure by 53.05% ~ 91.33% and increases the peak strength of coal across the tested confining pressure by 36.45% ~ 59%. Furthermore, this study found that hydrate formation kinetics are significantly enhanced in lignite compared to that in anthracite, which may be attributed to structural variations associated with the coalification degree. The underlying mechanism requires further research in the future. The data obtained in this study regarding the effect of hydrate formation under different initial conditions on coal seam properties demonstrate the feasibility of preventing gas disasters in coal via controlling the initial conditions.

Shale oil is one of the most promising alternative unconventional energies in the world, and Lucaogou Formation shows significant exploration potential, becoming the primary target in northwestern China. This paper compared the mechanical properties of shale layered samples from oil layer and interlayer of Lucaogou Formation, using uniaxial compressive tests with real-time micro-CT scanning. After that, the mineral analysis was conducted on one cross-section of the fractured sample to analyze the influence of mineral composition and distribution on micro-crack propagation. Such research has rarely been reported before. The results showed the surface porosity and elastic modulus of oil-bearing samples is larger than that of the interlayer samples, while the uniaxial compressive strength is lower. Besides, when there is only one dominant mineral with a content greater than 60%, a main crack tends to form at this area; When there are 2∼3 major minerals with a content of 10%–60%, a fractured zone with many fine micro-cracks is more likely to form here. Finally, the higher the Moh's hardness of the mineral, the more difficult it is for micro-cracks to develop through it.

In-situ conversion presents a promising technique for exploiting continental oil shale formations, characterized by highly fractured organic-rich rock. A 3D in-situ conversion model, which incorporates a discrete fracture network, is developed using a self-developed thermal-flow-chemical (TFC) simulator. Analysis of the model elucidates the in-situ conversion process in three stages and defines the transformation of fluids into three distinct outcomes according to their end stages. The findings indicate that kerogen decomposition increases fluid pressure, activating fractures and subsequently enhancing permeability. A comprehensive analysis of activated fracture permeability and heating power reveals four distinct production modes, highlighting that increasing heating power correlates with higher cumulative fluid production. Activated fractures, with heightened permeability, facilitate the mobility of heavy oil toward production wells but hinder its cracking, thereby limiting light hydrocarbon production. Additionally, energy efficiency research demonstrates the feasibility of the in-situ conversion in terms of energy utilization, especially when considering the surplus energy from high-fluctuation energy sources such as wind and solar power to provide heating.