Research on Optimizing the Water Injection Allocation of the Combined Well Pattern of Vertical and Horizontal Wells Based on Maximum Sweep Efficiency

The combined well pattern of vertical and horizontal wells has been widely applied in the offshore oilfield. Due to the heterogeneity of the reservoir, the difference of the orientation and distance between the injection and production wells and the difference of the water injection intensity, the effectiveness and water breakthrough time of each section of the horizontal production wells are different, and the conformance of water flooding is poor, which affects the development effect of the combined well pattern. Based on conformal transformation and potential superposition, a new method for optimizing the injection allocation is proposed to improve the sweep efficiency of the well. The new method is compared with the automatic distribution method and the specific proportion method by using the fine numerical simulation method. The analysis shows that the automatic allocation method is recommended when the water cut is <15%; when the water cut is 15–50%, it is recommended to use automatic allocation method or new method; When the water cut is >50%, the new method is recommended. The new method has been applied in X33H well group in B oilfield, and the effect of increasing oil production is remarkable, indicating that the new method has better applicability than the traditional method.