油水同层型致密油原始含油饱和度实验测定新方法及应用实例

A new method of underground oil saturation measurement for tight oil in the oil-water layer and a case study

探讨了保压取心岩心分析与核磁共振实验等常规实验方法在测定油水同层型致密油原始含油饱和度中的缺陷,对比了岩心含油饱和度与原始含油饱和度差异,明确了实验求取原始含油饱和度的关键为岩心离开地下原始状态后流体压力释放引起的挥发以及温度变化引起的散失。通过设计挥发性物理模拟实验与密度系数校正,以松辽盆地南部白垩系泉四段致密油密闭取心井位X井储层样品为实例,恢复了原始含油饱和度。实验结果显示,研究区最终原始含油饱和度平均值为43.1%,主要分布在40%~50%之间,相比密闭取心样品抽提含油饱和度平均值23.3%以及分布在10%~30%之间提高了20%。

The paper analyzes the disadvantages of underground oil saturation measurements for tight oil in the oil-water layer through some routine methods such as pressure-maintaining sealed coring and nuclear magnetic resonance and compares the difference between core oil saturation and underground oil saturation,which is detected to be caused by volatilization resulting from fluid pressure release and dissipation from temperature variation because the in-situ conditions could not be preserved.Here a new method is presented to restore underground oil saturation through physical simulation of volatilization and correction of density coefficient.This method is applied to oil saturation measurement for Cretaceous Quan 4sealed tight oil core samples acquired from Well X in south Songliao Basin.Restored underground oil saturation is43.1% on average and mainly distributes between 40% and 50%,which are 20% higher than the average value of 23.3% and the range of 10%-30% derived from sealed coring and extracting.