Numerical simulation of the multistage hydraulic fracturing and production in a tight gas horizontal well-history matching and preliminary optimization

In this paper a workflow and a numerical tool chain were developed for the design and optimization of multistage hydraulic fracturing in horizontal well, which have been widely used to increase the production from tight gas reservoirs. FLAC3Dplus was coupled with optiSLang and TMVOCMP for the history matching and optimization of hydraulic fracturing and gas production. The tool chain considers both the multiphase multicomponent flow and 3D coupled hydro-mechanical effects. The developed tool has been used to study the hydraulic fracturing and production in the tight gas reservoir XYZ in the North German Basin. Full 3D models were adopted for both hydraulic fracturing and subsequent gas production. The measured data during each stage of the treatment and 3.5 years' gas production history have been matched. The verified model was then used for optimization study by variation of the treatment schedule and fracture number/spacing. The investigation shows that not only FCD but also proppant distribution, geological structure and the interaction between fractures are determinant for the gas production. There is no unique criterion to determine the optimal number and spacing of the fracture, it should be analyzed in detail to the actual situation of individual reservoirs.