Stimulated Reservoir Volume Estimation and Analysis of Hydraulic Fracturing in Shale Gas Reservoir

Abstract

Hydraulic fracturing in horizontal well is the key technology for the commercial exploitation of shale gas reservoir. Stimulated reservoir volume (SRV) is an important indicator to evaluate the fracturing performance. However, estimating the SRV has been a long-standing challenge due to its complex forming mechanism. Most current SRV estimation methods are either expensive or time-consuming. This paper developed a 3D mathematical model to estimate the SRV by simulating the four main processes during shale fracturing—multiple hydraulic fractures propagation, formation stress variation, reservoir pressure lifting and natural fractures failure. In this model, hydraulic fractures propagation is calculated by pseudo-three-dimensional model, coupling with formation stress model; formation stress and reservoir pressure are obtained by displacement discontinuity method and Green’s function approach, respectively; natural fracture failure criterion is derived from Warpinski’s theory. This model not only considers the stress interference effect of multiple fractures, but also subdivides the SRV into shear-SRV and tensile-SRV according to the failure type of natural fractures network. This model was first implemented to a pilot well in the FL gas field in southwest China to estimate a SRV that matches well with the on-site monitoring microseismic signals. Then, this model was applied to FL gas field on a large scale to evaluate the overall fracturing effects. Finally, a sensitivity study was conducted to analyze the impact of engineering parameters on the SRV. This research explores an efficient method to estimate the SRV without high cost or complicated process and provides the theoretical basis and guidelines for pre-fracturing design and post-fracturing evaluation in shale gas reservoir.