密闭取心流体饱和度误差的影响因素及修正方法

在密闭取心过程中,由于流体压力和岩石应力的改变,导致流体脱气和岩石孔隙度改变,因此室内测定的岩心含水饱和度和实际油藏含水饱和度存在较大的误差,有必要将室内测定的含水饱和度校正到油藏条件下。以华北油田京271井降压脱气前、后含水饱和度的关系为基础,提出了新的密闭取心地面饱和度修正方法———室内物理模拟法,并且导出了考虑岩石变形对饱和度影响的修正公式,从而可以根据地面分析的饱和度推测储层地下饱和度真值。结果表明,油藏水淹程度及原油溶解油气比均对饱和度的计算结果产生影响,原油油气比越高,则饱和度误差越大。

Influencing factors and correction method for error of fluid saturation calculation during sealed coring

Because fluid pressure and rock stress change during sealed coring process, the degasification and rock pore volume change. As a result, there is difference between laboratory measuring saturation with in-situ saturation. Therefore the laboratory measuring fluid saturation has to be corrected to predict the in-situ fluid saturation. A new method called laboratory physical simulation method was given. A correlation of water saturation between pre-degassing and post-degassing for Jing 271 reservoir in Huabei Oilfield was obtained. And a formula was presented to predict in-situ fluid saturation in consideration of rock distortion. The results show that degree of water flooding and oil-gas ratio have an influence on the reckoning of water saturation. The higher the oil-gas ratio is, the bigger the saturation error is. The experimental results indicate that the laboratory physics simulation correction method is more accurate and effective.