聚合物驱后注气稳定重力复合驱数值模拟

Numerical simulation of gas injection for stable gravity flooding after polymer flooding

聚合物驱后剩余油分布高度零散、顶部油层剩余油难以动用,而聚驱后的主导技术尚无明确方法。在原油受力分析的基础上,提出了油藏顶部注气、底部三元复合驱的思路。针对大庆聚合物驱后区块,进行了不同驱替方式的预测对比研究。结果表明,注气稳定重力复合驱效果最好,提高采收率幅度达到了13.53%。对比不同驱替方式的顶部油层剩余油饱和度,注气稳定重力复合驱能够将顶部低渗透油层有效动用,剩余油大幅减少。分析不同时间点的纵向剩余油饱和度分布,顶部注气后利用纵向压差驱替剩余油向下运移,底部实施三元复合驱利用平面压差驱替剩余油,实现了立体驱替。注气稳定重力复合驱技术为聚驱后提高采收率技术的发展提供了新思路。

Residual oil after polymer fooding is very scattered, and residual oil in top sections of reservoir formations is extremely diffcult to develop, yet there is no prevailing technology suitable for development after polymer fooding. Based on analysis of stress on crude oil, the idea of injecting gas at the top section of the reservoir and conducting ASP fooding in bottom section has been proposed in this paper. Performances of different displacement modes have been predicted for some blocks of Daqing Oilfeld after polymer fooding. The research results show gas injection for stable gravity fooding has the best performance, with a EOR increment of 13.53%. Compar-ing residual oil saturation obtained through application of different displacement modes, gas injection for stable gravity fooding can effectively develop low-permeability formations in the top section and reduce residual oil signifcantly. Vertical distribution of residual oil saturation at different time points was analyzed. After gas injection in the top section, differential pressure in vertical direction may drive residual oil to migrate downward, while ASP fooding conducted in bottom section may drive residual oil by horizontal differen-tial pressure, thus realizing 3-dimensional fooding. Gas injection for stable gravity fooding may provide a viable option for EOR after polymer fooding.