Study on the method of step-up hydraulic fracturing infiltration for soft coal seam

Abstract

In view of the dilemma of the current hydraulic fracturing effect of soft coal seams, based on the existing hydraulic fracturing technology, a model corresponding to the jump pressure and the length of fracture propagation during the stepwise hydraulic fracturing process was constructed, the influence of the elastic modulus of coal and rock mass and the step-up pressure on the crack extension length during crack propagation was analyzed, and a step-up hydraulic fracturing infiltration method suitable for soft coal seam was formed. The research results show that the coal seam has strong stress sensitivity, and in the step-by-step step-up fracturing process, the coal seam cracks expand as the energy potential increases step by step, and they always extend along the direction of the maximum principal stress. The effect of infiltration is very obvious. In the process of fracture propagation, the elastic modulus of coal and rock mass, and the pressure difference of gradual jump have a great influence on the length of fracture propagation, and the initial crack width and crack height have a certain effect on the effect of fracture expansion and infiltration of the gradual jump hydraulic fracturing. The newly proposed step-up hydraulic fracturing and infiltration method can effectively extend the soft coal seam rock mass gradually when the cracks are fully developed, and has a good application prospect.