低渗水驱油藏水平井见水后产能研究新方法

New method for productivity study of horizontal well after water breakthrough in low permeability water flooding reservoir

在利用水平井开发低渗水驱油藏的过程中,油井见水是制约其产量的一个重要因素。基于Joshi水平井产能分析理论,将水平井三维渗流问题简化为2个二维平面渗流问题,考虑启动压力梯度,利用保角变换方法分别获得了2个二维平面内的产量公式,再结合水驱油藏中非活塞式驱替过程油水两相渗流特征,最终求得了低渗水驱油藏中水平井产油量计算新公式。通过实例计算与对比发现,本文公式与水平井单相经典产能公式计算结果虽然均比实际产油量大,但是本文公式计算结果与实际产油量相对误差最小,为2.94%,从而证明本文公式准确性较高、实用性较好。此项研究为低渗水驱油藏水平井见水后产量预测提供了新的思路。

During the development of low permeability water flooding reservoir with horizontal well, water breakthrough is an important factor to restrict the production. Based on the Joshi theory of productivity of horizontal well, this paper simplified 3D flow of horizontal well into two 2D flows; considering the start up pressure gradient, used conformal mapping method to obtain productivity formulas in two 2D flow planes respectively; combined with the flow characteristics of oil-water two phase during non-piston-like displacement in water flooding reservoir, eventually obtained a new produ- ction formula of horizontal well in low-permeability water flooding reservoir. Through case study and comparison, the results calculated by new formula and single-phase productivity formula of horizontal well are more than the actual output, but the result calculated by new formula has a small relative error with actual output, only of 2.94%. It demon- strates that the new formula has a high degree of accuracy and is very practical. The study will provide a new method for predicting the production after water breakthrough of horizontal well in low permeability water flooding reservoir.