疏松砂岩注水破裂机理及完整性研究

Study on Unconsolidated Sandstone Reservoir Water Injection Failure Mechanism and Well Integrity

常规的注水压力设计仅考虑裂缝开裂的压力,不能预测长期注水过程地层岩石物理参数及地应力的变化。从疏松砂岩注水过程近井筒周边受力分析入手,分析地层周边地应力及岩石力学性质变化,得到疏松砂岩在注水过程中拉伸及剪切破坏机理;并根据有效应力概念预测出地层孔隙度和渗透率变化。通过分析长期注水过程油藏及上覆盖层岩石物理性质及地应力的变化,建立以盖层的剪切破坏、拉伸破坏和断层的重新开启为依据的注水完整性分析模型。以乌干达Buffalo油田为例,通过数值模拟分析了地层参数及应力变化及不同注水压力敏感性分析,确定了该油田的安全注水压力,通过该方法大大提高了注水能力,在保证注水安全的情况下,为油田的增产增注提供了保障。

Conventional water pressure design method is only based on formation fracture pressure,the method cannot predict long-term formation parameters and stress changes when water injection.Based on near wellbore stress and formation parameter analysis,unconsolidated sandstone failure mechanism and porosity and permeability change in reservoir are gotten.Based on analysis of reservoir and cop rock parameter and stress change which longterm water injection influence on,fault re-active,tensile and compress failure of cap rock integrity model is established.A water injection model is constructed to simulate Uganda Buffalo oilfield water injection,reasonable and safe water injection pressure is gotten,and injectivity is greatly improved in safe condition by used this method.