Morphological Characteristics of Hydraulic Flushing under Multifactor Coupling and Its Enlightenment

Abstract

The shape of the hydraulic flushing hole is an important basis to determine the effective pumping radius. In the design and evaluation of the drilling hole, it is usually equivalent to a cylinder. However, the formation of the shape of the hole is affected by the gravity of coal and rock bulk, the friction of coal and rock, water force, stress, and other factors, so the scientific nature that is equivalent to a cylinder remains to be discussed. In this paper, based on the analysis of the whole process of hydraulic flushing and the formation of the pore shape, gravity, friction, water force, and ground stress of coal and rock bulk are selected as important factors affecting the pore shape, and the parallel Bergmark-Roos equation and PKN model are introduced to establish the BR-PKN equation of the pore shape of hydraulic flushing. MATLAB is used to reproduce the shape of the hydraulic flushing hole, which is a kind of ellipsoid with three different axes. In order to verify the accuracy of the hole shape, the YZD18.5 video imaging logging tool for mine lateral resistivity is used to collect and analyze the shape data of the hydraulic flushing hole, and the hole section is drawn, which is basically consistent with the theoretical derivation of the hydraulic flushing hole shape. COMSOL is used to simulate the hydraulic flushing equivalent of the ellipsoid hole compared with the cylinder hole under the same coal output and extraction time of 90 days. The extraction radius, desorption surface area, and effective extraction volume are 0.95, 0.79, and 1.14 times, respectively, providing a basis for the optimal design of hydraulic flushing.