Evaluation of Hydraulic Fracturing in Coal Seam Based on Time Difference-Particle Swarm Optimization Algorithm

Hydraulic fracturing (HF) technology is one of the key technologies to improve the permeability of coal seams, and microseismic (MS) source location is an effective method for evaluating the extent and effectiveness of HF. In this study, a new MS source location method is proposed based on the objective function by introducing a random weighting strategy: the time difference-particle swarm optimization (TD-PSO) location method. In this method, random inertia weight values, optimal candidate solution, and average evaluation value models are introduced, and asynchronous dynamic learning factors are proposed to improve the particle population diversity and convergence ability, which effectively avoids the tendency of the algorithm to fall into a local optimum. The convergence performance and search efficiency of the TD-PSO algorithm were verified using nonlinear multimodal functions. Through a large-scale field simulation of mine MS location tests, the search stability of the TD-PSO algorithm in 3D space and the accuracy of the seismic source location under the same monitoring data and test environment are verified, and the localization error is only 14.74 m. By evaluating the range of HF in the coal seams at Baijigou Mine, the fracturing ranges of YL1-1#, YL1-2#, and YL1-3# boreholes are 105, 45, and 75 m on the X-axis, and the fracturing ranges are 100, 50, and 80 m on the Y-axis, respectively, and the fracturing effect of YL1-1# borehole is the best. From the distribution of SRV value, the fracturing sections No. 2 and No. 4 of YL1-1# borehole have the best fracturing effect, which are 11210.47 and 4119.31 m(3), respectively.