Hydraulic Fracture Parameter Optimization of Shale Gas Reservoir Based on Orthogonal Test

Abstract

Parameters of hydraulic fractures affecting shale gas seepage in horizontal wells are interrelated. To solve the problem that traditional single factor analysis is difficult to describe the order and significance of hydraulic fracture parameters on shale gas seepage quantitatively, so the method of orthogonal test design was adopted. Based on double porosity model, effects of hydraulic fracture parameters after fracturing on shale gas seepage are analyzed though the finite element method quantitatively and qualitatively, and factors affecting shale gas seepage include hydraulic fracture half-length, width, permeability and spacing. Within the research scale of parameters, hydraulic fracture parameters affecting gas seepage in shale reservoir were optimized and the optimal combination was obtained according to the primary and secondary relationships. Results show that the order affecting shale gas seepage is: hydraulic fracture spacing, hydraulic fracture width, hydraulic fracture half-length equals to hydraulic fracture permeability, and the optimal combination is HFL(210 m), HFW(6 mm), KHF(6 × 10−11 m2) and HFS(100 m). It effectively communicates matrix and fracture, and also improves the seepage environment of shale gas, which is beneficial to the desorption of adsorbed gas in the matrix system at far end of the well, so that replenish reservoir and bottom hole flowing pressure timely and effectively. In conclusion, the results have certain guiding significance for optimal fracturing design of shale reservoir.