Li Hongjian, Deng Guangzhe
Key Laboratory of Western Mine Exploitation and Hazard Prevention Ministry of Education, Xi'an University of Science and Technology, Xi'an, 710054, Shanxi Province, China.
School of Energy Engineering, Xi'an University of Science and Technology, Xi'an, 710054, Shanxi Province, China.
Heliyon. 2024 Jul 27;10(15):e35377. doi: 10.1016/j.heliyon.2024.e35377. eCollection 2024 Aug 15.
The existence of hard rock layers has a serious impact on coal seam mining, in order to explore the acidification and crushing mechanism of hard sandstone rock layers, this paper adopts the self-developed CO-water-rock coupling test device to carry out the testing of mechanical properties and internal structural characteristics of rock samples before and after the coupling action of the three sandstones, and analyzes the influencing factors of sandstone CO coupling crushing. The study shows that: the lower the temperature of CO-water-rock coupling, the higher the pore pressure, the higher the volume fraction of CO in the coupling fracturing fluid, and the longer the coupling time, the greater the decrease in the mechanical strength of the rock samples, and the more complicated the splitting damage pattern is, and the CO-water-rock coupling makes the pore and fracture volume fraction and fractal dimension of three kinds of sandstone samples increase to varying degrees, whereas the volume fraction of minerals and the fractal dimension decrease, and the CO-water-rock coupling results in a decrease in the volume fraction of minerals and fractal dimension, and a decrease in the volume fraction of minerals and fractal dimension. The pore volume fraction and fractal dimension of the three sandstone samples increased to different degrees, while the mineral volume fraction and fractal dimension decreased, and the pore volume fraction and fractal dimension of the three sandstone samples decreased. The damage pattern of sandstone samples after coupling is affected by both chemical and mechanical damages. When using coupling fracturing fluid with 8 % CO, the degree of mineral dissolution and dissolution is the largest, and the dissolution effect is larger than the precipitation effect, which has the most significant effect on the morphology type and connectivity of microscopic pore cracks, and the study in this paper has certain theoretical and practical value for the chemical softening of sandstone.
硬岩层的存在对煤层开采有严重影响，为探究硬砂岩岩层的酸化及破碎机理，本文采用自主研发的CO - 水 - 岩耦合试验装置，对三种砂岩在耦合作用前后岩石样本的力学性质和内部结构特征进行测试，并分析砂岩CO耦合破碎的影响因素。研究表明：CO - 水 - 岩耦合温度越低、孔隙压力越高、耦合压裂液中CO体积分数越高、耦合时间越长，岩石样本的力学强度降低幅度越大，劈裂破坏形态越复杂，且CO - 水 - 岩耦合使三种砂岩样本的孔隙和裂隙体积分数及分形维数不同程度增大，而矿物体积分数及分形维数减小，三种砂岩样本的孔隙体积分数和分形维数不同程度增大，同时矿物体积分数和分形维数减小，三种砂岩样本的孔隙体积分数和分形维数减小。耦合后砂岩样本的损伤模式受化学损伤和力学损伤共同影响。当使用含8%CO的耦合压裂液时，矿物溶解及溶蚀程度最大，溶蚀作用大于沉淀作用，对微观孔隙裂隙的形态类型及连通性影响最为显著，本文研究对砂岩的化学软化具有一定的理论和实际价值。
