低渗透油藏注水对水平地应力的影响

The effect of water injection on horizontal terrestrial stress in low permeability reservoirs

油气田开发过程中,地应力(特别是2个水平主地应力)受注水等因素影响状态发生改变,对油气生产产生较大的影响。由于在低渗透油藏中存在启动压力梯度,注水过程是一个含动边界的渗流问题,利用油藏压力分布近似表达式,研究了低渗透油藏注水过程孔隙压力随时间、空间的变化规律,推导出2个水平主地应力随地层孔隙压力变化的理论公式,得到了水平主地应力随时间、空间的变化规律。

The state of terrestrial stress, especially the two main horizontal stresses, may change during oilfield development process as a result of water injection and has a great impact on oil and gas production. Because of the threshold pressure gradient in low permeability reservoirs, water injection process is a percolation issue concerning flow boundary. The changes of pore pressure with time and space are studied for water injection process in low permeability reservoirs by using the approximate equation of reservoir pressure distribution. The theoretical equation of the change of the two main horizontal terrestrial stresses with pore pressure has been derived, and the change of the main horizontal terrestrial stress with time and space is understood.