致密油藏注CO2增能效果及参数优化

Energy Enhancement Effect and Parameters Optimization of CO2 Injection in Tight Oil Reservoir

为了研究致密油藏注CO 2增能效果,利用长庆油田陇东P区块致密砂岩岩心开展核磁共振实验、扫描电镜实验,分析CO 2对储层孔隙结构的影响规律;通过相态计算,分析CO 2注入对原油体积系数及饱和压力的改变。运用有限差分方法和三维有限元方法,建立三维动态地应力与油藏双向耦合模型,分析储层渗透率变化规律及井底附近压力分布特征;通过建立目标区块储层注CO 2增能图版,评价注CO 2增能效果,优化注入参数。结果表明:CO 2主要通过溶解、冲蚀作用使岩心大孔隙数目增加;注入10%~45%不同摩尔分数的CO 2可使原油体积膨胀至1.19倍,原油饱和压力增加86%;注CO 2对目标区块储层增能效果明显,目标区块的最佳注气体积为700 m 3,最佳注入速度为4 m 3/min。

In order to study the energy enhancement effect of CO 2 injection in tight reservoir,both the nuclear magnetic resonance experiment and the scanning electron microscope experiment were carried out on the tight sandstone core samples in Longdong Block P of Changqing oilfield.The effect of CO 2 on the pore structure of tight oil reservoirs was clarified.The changes of expansion and saturation pressure of crude oil caused by CO 2 injection were analyzed by phase behavior calculation.The finite difference method was applied to the reservoir pressure and saturation,and the three-dimensional finite element method was applied to calculate the reservoir geologic mechanics parameters.The three-dimensional dynamic two-way coupling model was established to analyze the permeability change of reservoirs affected by geological stress and the pressure distribution rule near the bottom of the well.A pressurize effect chat of CO 2 injection for the target area was established as a reference for injection parameter optimization.The experimental results show that the number of macropores increases mainly through dissolution and erosion after CO 2 injection.Phase behavior calculation results show that injection of CO 2 with different mole fractions of 10%to 45%can expand the volume of crude oil to 1.19 times,and the saturation pressure of crude oil increases significantly by about 86%.The simulation results show that CO 2 injection can increase energy significantly.The optimal gas injection volume and injection speed in Target Block are 700 m 3 and 4 m 3/min respectively.