Study on coal mechanical damage law and anti-reflection effects under fracturing fluid corrosion affecting

In order to improve the permeability enhancement effect of low permeability coal seams，the traditional hydraulic fracturing technology of coal seam is improved by using surfactant and acid solution to corrode the coal，and the corrosive fracturing fluid is used to enhance the damage effect of the fracturing fluid in the coal body，revealing the mechanical change characteristics of the corrosive coal. The anti-permeability technology of coal based on fracturing fluid corrosion is industrially applied in the coal mine site，and the effect of coal seam anti-permeability and gas drainage is investigated. The research results show that the failure process of coal samples corroded by fracturing fluid is divided into four stages：fracture closure stage，elastic deformation stage，stable fracture propagation stage and accelerated crack propagation stage，the corrosive fracturing fluid penetrates deep into the pores and fissures inside the coal rock，reacts with the clay minerals and inorganic salt minerals and other impurity minerals in it，causing the destruction of the coal rock cavities and fissures，resulting in the appearance of non-penetrating fissures in the coal sample. After the corrosion treatment，the stress value of the coal sample in the stable expansion stage of the crack during the failure process becomes smaller，and the strength of the coal sample decreases. The lowest，indicating that SDS has a positive effect on the corrosion effect destroying the coal structure. It can be seen through industrial tests that，compared with ordinary hydraulic fracturing holes，acid corrosion fracturing holes maintain a high concentration and high flow for a long time and decay slowly. The concentration of pilot holes in the fracturing-affected area is up to 76%; the average gas concentration is 8% higher than that of hydraulic fracturing holes，and the drilling spacing is expanded from 6 m to 11 m，saving coal mine gas control costs.