特低渗非均质油藏CO_2驱注气速度对采出程度的影响

Influence of CO_2 flooding gas injection rate on recovery percent in extra-low permeability heterogeneous reservoir

特低渗非均质油气藏具有低孔、低渗、低饱和度和低产等特征,利用常规水驱开发难度大,采收率低,而CO2驱油能显著提高特低渗非均质油藏的采出程度。根据特低渗非均质油藏的地质和储层特征,利用双层非均质岩心模拟油藏非均质性,设计完成了5种不同注气速度下(1、2、4、8、10 m L/min)的驱替实验,系统分析了CO2驱油速度对原油采收率的影响。结果表明,CO2驱提高采收率幅度最大段在CO2窜流之前,随着注气速度的变大,推进速度变快,突破时间逐渐前移;合理的驱替速度使得CO2气体与岩心孔隙中水及原油的接触时间变长,采收率提高,从而提高特低渗非均质油藏开发的经济效益。

Since extra-low permeability and heterogeneous reservoirs are characterized by low porosity, low permeability, low saturation and low production, utilizing conventional water lfooding has big development dififculties and low recovery ratio, while CO2 lfooding can improve the recovery percentage of extra-low permeability and heterogeneous reservoirs signiifcantly. According to the geological and reservoir characteristics of extra-low permeability and heterogeneous reservoirs, and double-layer heterogeneous cores were used to simulate the heterogeneity of reservoirs and displacement experiments under 5 different gas injection rates (1, 2, 4, 8 and 10 mL/min) were designed and completed for systematic analysis of the inlfuence of CO2 lfooding on oil recovery ratio. Research results indicate that the largest recovery ratio increase by CO2 lfooding occurs before CO2 channeling, and as the gas injection rate rises, the advance rate increases and breakthrough time leads forward gradually. Reasonable rate of displacement makes contacting time of CO2 and water and crude oil in the core porosity, and recovery ratio be improved, and thus improves the economic beneifts of the development of extra-low permeability and heterogeneous reservoirs.