A New Fracture Parameter Optimization Method for the Horizontal Well Section of Shale Oil

Abstract

Hydraulic fracturing is the most prominently used technique for increasing well productivity in shale oil reservoirs. Therefore, studying the method for optimizing fracture parameters is essential in the development of shale oil. This study established a mathematical model of non-Darcy flow in the fractured horizontal well section of a shale oil reservoir which considered the influence of the threshold pressure gradient. The finite element method was used to solve the problem, and the calculation method of pressure field and productivity was given. This model is used to study the optimal number of clusters, optimal cluster spacing, optimal fracture length, and optimal fracture conductivity in a horizontal well section. Simulation shows that the optimal number of clusters in a horizontal well section is five when the permeability is 0.02 × 10–3 μm2–∼0.10 × 10–3 μm2, and the optimal number is four when the permeability range is 0.15 × 10–3 μm2–∼0.30 × 10–3 μm2. With the increase in the number of clusters, the stimulation effect is more sufficient, the interference effect between fractures is enhanced, and the loss of stratum energy is accelerated. The optimal cluster spacing is 30 m. Several cases of non-uniform cluster spacing have little effect on the stimulation effect. The cluster number and the sum of the cluster spacing are the determinant factors affecting the stimulation effect. The optimal fracture half-length is 140 m. Several cases of the non-uniform fracture length have little effect on the stimulation effect. The cluster number and the sum of the length of the fracture are the determinant factors affecting the stimulation effect. The optimal conductivity is 20 D•cm. At last, it proposed a fracture parameter optimization method considering the stratum energy loss and productivity.