不同驱替阶段微观剩余油赋存特征及影响因素

Occurrence Characteristics and Influencing Factors of Micro Remaining Oil in Different Displacement Stages

为进一步明确中高含水期油藏微观剩余油分布特征,将CT无损分析和常规驱替实验相结合,利用原位对比技术分析不同驱替阶段的微观剩余油分布特征及其影响因素。结果表明:微观剩余油动用效果受微观孔喉大小、孔喉连通性以及孔喉空间分布等方面的影响,各种微观力形成的主驱动力与微观孔喉结构共同影响剩余油的分布情况及赋存特征;水驱阶段动用效果主要受微观孔隙结构影响,连通性较好的大孔道中微观剩余油可发生长距离搬运,动用效果好,而连通较差的小孔道中油滴仅会沿边缘发生小幅度的减薄,动用效果较差;聚合物-表面活性剂复合驱后再进行水驱,微观孔喉分布的非均质性是影响其动用效果的最重要因素,微观非均质性强的低渗、高渗岩心动用效果更明显;油田不同开发阶段应采取不同注采策略,水驱阶段应选取均质且大孔道发育层段进行水驱开发,聚合物-表面活性剂复合驱阶段应优先选择水驱波及效果差、非均质性强的层段进行开发。研究结果对储层微观剩余油赋存及提高采收率研究具有指导意义。

In order to further clarify the detailed description of the distribution characteristics of the micro remaining oil in the reservoir in the middle and high water-cut stage,CT nondestructive analysis was combined with conventional displacement test to analyze the distribution characteristics and influencing factors of micro remaining oil in different displacement stages by means of in-situ comparison technology.The results show that the production effect of micro remaining oil is affected by the size of micro pore throat,the connectivity of pore throat and the spatial distribution of pore throat,etc.The characteristics of remaining oil distribution and occurrence are affected jointly by the main driving force formed by various micro forces and the micro pore throat structure.In the water flooding stage,the production effect is mainly affected by the micro-pore structure,the micro remaining oil in the large pore channel with good connectivity can be migrated for a long distance,with high production effect,while the oil droplets in the small channels with poor connectivity will only be thinned slightly along the edge,with poor production effect.Polymer-surfactant composite flooding is followed by water flooding is conducted,the heterogeneity of micro-pore throat distribution is the most important factor affecting the production effect,and the production effect of low-permeability and high-permeability cores with high micro-heterogeneity is more obvious.Different injection and production strategies should be applied in different development stages of the oilfield.Homogeneous intervals with large pores should be selected for development in water flooding stage,while heterogeneous intervals with poor water flooding sweep effect should be preferentially selected for development in the polymer-surfactant composite flooding stage.The results of the study are of guiding significance for the occurrence and enhanced oil recovery of micro remaining oil in the reservoirs.