考虑应力敏感性的低渗透油藏油井产能分析

Analysis on oil well productivity of low-permeability reservoirs with stress-sensitivity being taken into considerations

刘峰 王裕亮 陈小凡 苏云河 王玥

Liu Feng Wang Yuliang Chen Xiaofan Su Yunhe Wang Yue

低渗透油藏的单井产能主要受储层应力敏感性的影响。油藏流体采出后,地层压力下降,有效应力增加,孔隙度和渗透率均降低,导致油井产能下降。笔者在只考虑基于渗透率降低对低渗透油井产能方程影响的基础上,考虑了孔隙度随应力变化对油井产能的影响,建立了同时考虑渗透率和孔隙度的产能应力敏感性方程,并提出了产能-应力敏感性指数的概念。随着低渗透储层应力敏感性的增强,应力敏感性常数增大,产能-应力敏感性指数同时增大,油井的日产油量迅速降低。新的产能-应力敏感性方程使低渗透油藏油井产能计算结果更加简化和准确。通过实例验证与分析,产能-应力敏感性指数对低渗透油藏单井产能有较强的影响,随着产能应力敏感性指数的增加,油井的无阻流量下降速度降低。与只考虑渗透率降低的油井产能方程相比,新方程更能反映低渗透油藏的实际生产情况,对合理开发低渗透油藏具有一定的指导意义。

Stress-sensitivity is one of the main factors that affect single well productivity in low-permeability rese-rvoirs.It is common sense that wells tend to produce less after certain volumes of reservoir fluids were recovered as that would cause drop-down in formation pressure,porosity and permeability and increase of effective stress.The authors modified the previous productivity function of low-permeability oil wells that only considers the influences of permeability decrease by incorporating the influences of stress on porosity,established a new stress-sensitive productivity function with both porosity and permeability being taken into consideration,and proposed the concept of productivity-stress-sensitivity index.Along with the intensifying of stress-sensitivity of low-permeability reservoirs and increase of stress-sensitivity constant,the productivity-stress-sensitivity index also enlarges,and daily oil production quickly shrinks.The new function simplifies the calculation process and improves the accuracy.Practices show that the productivity-stress-sensitivity index exerts a strong influence upon the productivity of wells in low-permeability reservoirs.As the index increases,the decreasing of open flow capacity of oil wells slows down.Compared with the old function,the new one reflects better the actual production of low-permeability reservoirs and therefore could be used to guide their development.

10.11743/ogg20130117