X区块低渗油藏CO_(2)混相驱影响因素分析

Influencing Factors of CO_(2) Miscible Flooding in Low Permeability Reservoirs in Block X

为研究X区块低渗油藏注CO_(2)混相驱的影响因素,通过开展室内实验分析注入气CO_(2)与地层流体的最小混相压力,分析接触时间、渗透率、非均质性、杂质气体对CO_(2)混相驱油的影响,为X区块低渗油藏注CO_(2)提供理论依据。实验主要得到以下结论:通过细管实验测定得到该区块的最小混相压力为17 MPa。接触时间、渗透率和杂质气体会影响CO_(2)混相驱的效果,CO_(2)与地层流体的接触时间越长,CO_(2)与地层原油的混相效果越好。低渗油藏中CO_(2)混相驱的效果优于中高渗油藏。非均质性对混相的影响较小。CO_(2)混相压力随N_(2)及CH_(4)的摩尔分数的增大而升高,随C_(2)及C_(4)摩尔分数的增加而降低,注入气CO_(2)的纯度应该在95%以上,以上分析为目标区块后续注CO_(2)混相驱油提供了理论依据。

In order to study the influencing factors of CO_(2) miscible flooding in low-permeability res-ervoirs in Block X,this paper conducts laboratory experiments to analyze the minimum miscible pressure of injected gas CO_(2) and formation fluid,and analyzes the contact time,permeability,heter-ogeneity,and impurity gas on CO_(2).The influence of miscible flooding provides a theoretical basis for CO_(2) injection in low-permeability reservoirs in Block X.The main conclusion of the experiment are as follows:the minimum miscible pressure of this block is 17 MPa determined by the thin tube ex-periment.The contact time,permeability and impurity gas will affect the effect of CO_(2) miscible flooding.The longer the contact time of CO_(2) and formation fluid is,the better the miscibility effect of CO_(2) and formation crude oil becomes.The effect of CO_(2) miscible flooding in low permeability reser-voirs is better than that in medium and high permeability reservoirs.Heterogeneity has less effect on miscibility.The CO_(2) miscible pressure increases with the increase of the mole fraction of N2 and CH_(4),and decreases with the increase of the mole fraction of C2 and C4.The purity of the injected gas CO_(2) should be above 95%.The above analysis provides a theoretical basis for subsequent CO_(2) injection miscible flooding in the target block.