Experimental Study on Damage Mechanism of Fracturing Fluid in CBM Reservoir of Eastern Yunnan and Western Guizhou

Abstract

The fracturing of CBM reservoirs can bring some damage because of the loss, intrusion reservoirs and difficult flowback of fracturing fluid. In this paper, damage evaluation experiment of different fracturing fluid on different structure of coal were conducted adopting active water and polymer fracturing fluid which were commonly used in the field. The microstructure of coal sample treated with different fracturing fluid was investigated by scanning electron microscopy (SEM). The microscopic mechanism of fracturing fluid damage to coal fractures and matrix pores was discussed. The results of these tests have shown that the damage of the active water fracturing fluid to the pore structure of coal sample is larger than that of polymer fracturing fluid, but the damage is generally less than 40%. The damage of polymer to fracture is higher than that of matrix. The effect of fracture fluid inorganic salt crystallization, polymer adsorption and water wet expansion can make the matrix pore and fracture decrease, thus damaging the seepage structure and reducing the coal permeability. But the gap between the original structure of microcracks and matrix pores is large, the impact of pollution on them is also quite different. The conclusion of this study is helpful to evaluate the effect of fracturing fluid on coalbed methane mining comprehensively and has a positive significance for the optimization of fracturing fluid formulation.