Numerical investigation for simultaneous growth of hydraulic fractures in multiple horizontal wells

摘要

Recently developed multi-well fracturing technologies are widely used in unconventional low-permeable reservoirs for enhancing production. In this paper, we have implemented a three-dimensional numerical model, which couples the rock deformation, fluid flow and the dynamical flux partition in multiple wellbores, to simulate the simultaneous growths of hydraulic fractures in multi-well fracturing at unconventional reservoirs. To resolve the fully-coupled problem, a numerical scheme with four-layer loops is adopted in this model. The numerical simulations reveal that the asymmetric fracture propagations occur in multi-well fracturing, and the lateral growths of interior fractures are suppressed due to the intense inter-well stress interference. Results show that higher inlet pressure loss, achieved by limited entry design, is able to promote the lateral propagation of interior fractures. Then, case studies are performed to investigate the influences of fracture spacing, well spacing and fracturing scheme on fracture growths in multi-well fracturing. The results reveal that, when decreasing fracture spacing to a certain degree, the fracturing efficiency will not be promoted further by increasing fracture number. The case studies also indicate that, for successful fracturing treatment, a possible lower limit of well spacing should be considered in design, to avoid a sharp reduction of effectiveness in treatment. Compared to simultaneous fracturing scheme, study results show that zipper fracturing scheme has a better performance in promoting the fracture complexity and increasing the fracture surface area, which is favorable to enhance hydrocarbon production.