页岩油水平井压裂渗吸驱油数值模拟研究

Numerical Simulation of Oil Displacement by Fracturing Imbibition in Horizontal Shale Oil Wells

欧阳伟平 张冕 孙虎 张云逸 池晓明

OUYANG Weiping ZHANG Mian SUN Hu ZHANG Yunyi CHI Xiaoming

中国石油集团川庆钻探工程有限公司长庆井下技术作业公司，陕西西安 710018 低渗透油气田勘探开发国家工程实验室，陕西西安 710018 中国石油集团川庆钻探工程有限公司，四川成都 610051

Changqing Downhole Service Company, CNPC Chuanqing Drilling Engineering Company Limited, Xi’an, Shaanxi, 710018, China National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields, Xi’an, Shaanxi, 710018, China CNPC Chuanqing Drilling Engineering Company Limited, Chengdu, Sichuan, 610051, China

为了提高压裂页岩油水平井产量预测精度、优化闷井时间及压裂液用量等参数，建立了一种考虑压裂液注入、闷井渗吸及开井生产的压裂页岩油水平井油水两相渗流数学模型，利用控制体积有限元法求其数值解，模拟了渗吸作用下基质–裂缝油水置换的过程，获得了油水压力场、速度场、产量及含水率的动态变化。分析了压裂渗吸驱油特征，优化了闷井时间和压裂液用量，并研究了基质渗透率和缝网复杂程度对渗吸驱油的影响。研究结果表明：毛细管力越大，闷井时间越长，则含水率越低，渗吸增产作用越明显；压裂液用量增加能够提高渗吸驱油产量，但同时会引起含水率升高，可通过含水率和产量增幅确定压裂液合理的用量；最优闷井时间受毛细管力、基质渗透率和缝网复杂程度的影响，其中毛细管力和基质渗透率决定了渗吸速度，而缝网复杂程度决定了渗吸面积。所建立的渗吸油水两相渗流模型可为页岩油水平井压裂优化设计提供依据。

To improve the production prediction accuracy of fractured horizontal shale oil wells and optimize parameters such as shut-in time and fracturing fluid volume, a mathematical model of oil-water two-phase flow considering the whole process of fracturing fluid injection, shut-in imbibition, and well-opening production was built. Its numerical solution was obtained with the control volume finite element method, and the oil-water displacement between the matrix and fractures by imbibition was simulated to obtain the dynamic changes of the oil-water pressure field, velocity field, production, and water cut. The characteristics of oil displacement by fracturing imbibition were analyzed, and the shut-in time and fracturing fluid volume were optimized. In addition, the effects of matrix permeability and fracture network complexity on oil displacement by imbibition were examined. The research results show that in the case of a larger capillary force and longer shut-in time, the water cut is lower and the imbibition stimulation effect is more noticeable. The increase in fracturing fluid volume can promote the production of oil displacement by imbibition, while it will raise the water cut at the same time. Thus, the reasonable fracturing fluid volume can be determined by the increments of water cut and production. The optimal shut-in time is affected by the capillary force, matrix permeability, and fracture network complexity. To be specific, the capillary force and matrix permeability determine the imbibition velocity, while the fracture network complexity regulates the imbibition area. The model built in this paper can provide references for the optimal design of horizontal shale oil well fracturing.

https://doi.org/10.11911/syztjs.2021083