大庆外围低渗透裂缝性油藏含水率预测方法

Prediction method of water cut of low-permeability fractured reservoirs in periphery Daqing Oilfield

大庆外围低渗透裂缝性油藏同时具有储集油气的基质系统和作为渗流通道的裂缝系统,与非裂缝性油藏相比具有特殊的含水率变化趋势,常规含水率预测方法不适用。依据低渗透裂缝性油藏油水两相渗流特征,提出了基质、裂缝系统相渗复合方法,给出大庆外围低渗透裂缝性油藏复合相对渗透率曲线,然后根据油藏工程理论,推导出含水率、采出程度计算公式,建立了裂缝性油藏含水率预测方法,结合大庆外围朝阳沟油田低渗透裂缝发育区块进行了实例计算与分析。结果表明,基于复合相渗的含水率预测方法预测相对误差为4.47%,与现有方法中误差最小的水驱规律曲线相比,计算精度提高了2.26百分点,能够较为准确地预测低渗透裂缝性油藏含水率。研究成果为裂缝性油藏开发决策和开发规划提供了理论依据。

Low-permeability fractured reservoirs in periphery Daqing Oilfield have matrix system for oil and gas storage and fracture system as flow channel,which exhibit special water cut variation trend compared with non-fractured reservoirs,and conventional water cut prediction methods are not applicable. Based on characteristics of oilwater two-phase flow in low-permeability fractured reservoirs,a method of composite relative permeability of matrix and fracture systems is proposed,providing composite relative permeability curves for low-permeability fractured reservoirs in periphery Daqing Oilfield. Then based on reservoir engineering theory,formulas for calculating water cut and recovery percent(OOIP)are derived,and a method for predicting water cut in fractured reservoirs is established,which is combined with calculation and analysis case of low-permeability fractures-developed blocks in Chaoyanggou oilfield of periphery Daqing Oilfield. The results show that prediction method for water cut based on compound relative permeability has relative prediction error of 4.47%,increasing calculation accuracy by 2.26 percentage points compared with water flooding law curve method with minimum error among current methods,and can accurately predict water cut of low-permeability fractured reservoirs. The research provides theoretical evidence for development decision-making and development planning of fractured reservoirs.