Study on the Impact of Flow Dynamic Allocation Mechanism on the Balanced Propagation of Multicluster Fractures in Horizontal Wells

Abstract

The implementation of the multicluster fracturing technique in horizontal wells is crucial to the economic development of shale gas reservoirs. The stress shadow area generated by them suppresses the effective expansion of fractures, leading to lower construction quality. Numerous well logging and production data indicate that dynamic flow allocation is also an important mechanism restricting oil and gas production. To reveal the mechanism of multifracture synchronous competitive expansion, a multifracture expansion finite element model considering fluid-solid coupling in porous media was established. A wellbore model was built to characterize the fluid pressure drop, incorporating pipe flow and fluid connection elements to emulate fluid flow within the wellbore, and the influence of various factors on the balanced expansion of fractures was investigated. The results show that high porosity, uniform perforation, and high elastic modulus of sweet spots are favorable for the balanced expansion of multiple fractures when using high-volume and low-viscosity fracturing fluids. When the spacing is small and the porosity is low with nonuniform perforation, the threshold generated by perforation friction will dominate the balanced fluid injection and expansion of each fracture. The horizontal well fracturing plan in a certain area of southwest China was optimized using this model. After optimization, when the spacing is less than 15 m, the total number of perforations is 32, and the average injection rate per cluster will be increased by 0.125 m3/min, with a coefficient of variation of 3.9% among clusters. When the perforations are nonuniformly distributed, the average injection rate per cluster will be increased by 0.101 m3/min, the fluid inflow difference coefficient of each cluster is 4.1%, and multiclusters will have a uniformly developed fracture network. This study has certain guiding significance and reference value for the balanced expansion of multifractures in horizontal wells.