Abstract
Shale reservoirs have diverse mineral types, and analyzing the sensitivity of the mineral composition to shale pores is of great scientific and engineering significance. In this paper, first, X-ray diffraction (XRD) experiments on shale mineral compositions are carried out, and the characteristics of pore structure changes after shale mineral compositions interacted with external fluids (slick water and backflow fluid) are elucidated. Then, the effects of quartz, kaolinite, and pyrite on the pore structure and permeability of shale on the susceptibility to slick water are studied. The results show that (a) quartz and clay minerals are the dominant constituents of each core, with some cores containing minor amounts of plagioclase feldspar and rhodochrosite. (b) The composition of the shale changed significantly following the action of external fluids. The average quartz content of pure shale decreased from 31.62% to 29.1%. The average content of quartz in siliceous shale decreased from 36.53% to 33.5%. The average content of quartz in carbonaceous shale decreased from 9.15% to 8.05%. (c) Factors affecting the sensitivity of shale pore structure and permeability to slick water are mainly quartz, kaolinite, and pyrite. The contents of quartz, kaolinite, and pyrite decreased by an average of 5.1%, 4.6%, and 0.9%, respectively, after slick water action.