安塞地区加密井地层压力预测研究

Research on Formation Pressure Predictionin in Ansai Area Infilling

安塞油田王窑加密试验区位于王窑区块中西部,开发时间较长,综合含水58.9%,地质储量采出程度11.8%,地层压力系统紊乱,且同时存在天然裂缝和压裂裂缝,加密试验井地层压力预测难度大,安全钻井风险高。在分析安塞加密试验区地质特征的基础上,针对注水过程中地层压力与原始地层压力差异较大,且经过注水后的地层压力分布难以准确确定的问题,将裂缝性地层渗流理论引入到注水后地层压力预测过程中,给出了复杂裂缝地层加密井地层渗透率的张量计算方法和加密井地层压力预测方法,对安塞试验区加密井地层压力进行了预测,预测结果精度较高,能够满足确定安全钻井液密度窗口的需要;并分析了裂缝特征对加密井地层压力的影响,可为加密井安全钻井提供实际指导。

Ansai Oilfield infill experimental zone is located in the mid-west Wangyao zone. After long-time development, the composite water cut reaches 58.9%, geological reserves recovery degree 11.8% ; formation pressure system is in disorder, and natural fracture and fracture cracks co-exist. Therefore, the prediction of formation pressure of encryption test wells is difficult and drilling safety is at risk. Based on the analysis of Ansai experimental area and on the basis of geological charactelistics, we studied the difference between formation pressure in the process of water injection and the original formation pressure, trying to accurately determine reservoir pressure distribution water after injection. We introduced the seepage theory of fractured formation after water injection in the process of the formation pressure prediction, and suggest calculation method for infilled wellbore formation permeability tensor of complex crack formation and prediction methods for infilling of formation pressure. Applying these methods to the prediction of formation pressure of experimental zone in Ansai produced highly accurate results that satisfy the need of safe drilling fluid density window The influence of the characteristic of cracks on infill well formation pressure is also analyzed, which can provide practical guidance for infill well drilling safety.