综采工作面砂岩夹矸层酸化压裂破碎机理

Fracture mechanism of acid fracturing of sandstones gangue layer in fully mechanized mining face

以榆林小保当矿区112201大采高工作面煤层砂岩夹矸层为研究对象,通过夹矸层砂岩物理力学化学性质综合性实验分析,提出了以微量CO2水合物为主的复配专用岩石酸化压裂方法。对高压CO2耦合溶液作用下砂岩中矿物溶蚀的物理化学机理进行研究,分析了高压酸化压裂引起的岩石微观结构变化共同作用下的岩层变形破坏特征及孔渗影响规律。结果显示:CO2水合物酸化专用压裂方法,对夹矸砂岩组成中方解石和白云石组分的影响显著,高岭石膨胀作用增强,压裂液溶蚀孔隙数量显著增多,孔径变大,综合孔隙度和渗透率均增大。通过开采验证,煤层夹矸层CO2耦合压裂破碎后,与正常回采区段及常规水压致裂区段相比,耦合压裂区段工作面回采率显著提高,同时节能降耗效果最为明显。

Taking the coal seam sandstone intercalated gangue layer at 112201 large mining height face in Xiaobaodang Mining Area of Yulin as the research object, the special rock acid fracturing method based on trace CO2 hydrate is proposed through the comprehensive experimental analysis of the physical, mechanical, and chemical properties of the sandstone in gangue layer. The physical and chemical mechanism of mineral dissolution in sandstone under the action of high-pressure water fracturing fluid was studied, and the deformation and failure characteristics of the rock layer and the law of pore-permeability under rock microstructure changes caused by the action of high-pressure acid fracturing and were analyzed. The results show that the special fracturing method for CO2 hydrate acidification has a significant effect on the calcite and dolomite components in sandstone gangue composition, the kaolinite expansion is enhanced, the number of pores dissolved by the fracturing fluid is significantly increased,the pore diameter becomes larger, both composite porosity and penetration rate increase. Through mining verification, the coal extraction rate and average raw coal production are significantly improved after acid fracturing in the coal gangue layer, and the reduction of cutting energy consumption of the shearer is the most obvious.