Numerical modeling of hydraulic fracture containment of tight gas reservoir in Shihezi Formation,Linxing Block

During the process of fracturing the layered tight gas reservoirs with shale seams,the propagation of hydrau- lic fractures can be significantly affected by the geological factors (in-situ stress difference between inter-layers,rock deformability etc. ),and also some operation parameters (injection rate,fracturing fluid viscosity,perforation positions etc. ). In this paper,a three-dimensional fracture height model of layered tight gas reservoirs has been constructed based on the ABAQUS software to investigate how these factors influence the propagation and geometry of hydraulic fractures. The data sample is from Linxing block on the east margin of Ordos Basin. The simulation result shows that many vertical fractures can be created during the treatment, and the fracture height is dominated by in-situ stress difference. In-situ stress difference higher than 4 MPa shows a great effectiveness in fracture height containment. In ad- dition,the results indicate that lower elastic modulus is favorable for fracture height containment,while Possion’s ratio has almost no effect on it. The propagation of hydraulic fractures is strongly inhibited with in-situ stress difference higher than 4 MPa and injection rates lower than 6 m3 / min. However,with the in-situ stress difference dropping to 2 MPa or even lower,the fracture height grows well with increasing injection rates. The simulation also finds that frac- turing liquid with its viscosity lower than 10 mPa·s has negligible impact on fracture height. Perforation position plays an important role in the fracture initiation stage. Fracture geometries differ a lot with different perforation schemes. Bar- ring the numerical simulation,the authors have conducted many indoor experiments of which the results fits the simula- tion results well. The study of hydraulic fracture initiation and propagation in multi-layers reservoir can provide a refer- ence for the field prediction of fracture geometry and optimization of pump injection program.