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

Abstract

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.

Keywords

• gangue in coal seams
• acid fracturing
• rock experiment
• cracking pressure
• hydraulic fracturing