超临界CO_(2)/H_(2)O混合流体吞吐提高页岩油采收率实验研究

Experimental study on enhancing shale oil recovery by supercritical CO_(2)/H_(2)O mixture huff and puff

针对页岩储层压裂后一次衰竭开发原油采收率低的问题,基于页岩储层的低孔、超低渗透特征,提出了超临界CO_(2)/H_(2)O混合流体吞吐提高页岩油采收率实验方法。通过自主设计的室内岩心实验评价超临界CO_(2)/H_(2)O混合流体吞吐页岩油的效果,并对实验过程中注入介质、焖井时间、注入压力、吞吐轮次对提高采收率的影响规律进行研究,同时通过核磁共振技术明确超临界CO_(2)/H_(2)O混合流体对不同孔隙类型中原油的动用程度。结果表明:超临界CO_(2)/H_(2)O混合流体吞吐可以有效提高页岩油采收率;对于物性较差的页岩岩心,焖井时间对提高采收率有较大影响;注入压力与超临界CO_(2)/H_(2)O混合流体的扩散速度和渗流能力密切相关,混相条件下提高采收率效果显著;增加吞吐轮次大孔隙中的原油动用效果较好,但无法通过增加吞吐轮次动用更多微小孔隙中的原油。

Aiming at the problem of low oil recovery in shale reservoir with primary depletion development after fracturing,an experimental method of supercritical CO_(2)/H_(2)O mixture huff and huff to enhance shale oil recovery was proposed based on the low porosity and ultra-low permeability of shale reservoir.In this paper,the effect of supercritical CO_(2)/H_(2)O mixture on huffing and puffing shale oil was evaluated by indoor self-designed core experiment,during which the influence of injection medium,soaking time,injection pressure and huff and puff cycles on enhanced oil recovery(EOR)was studied.At the same time,the producing ratio of oil in different pores by supercritical CO_(2)/H_(2)O mixture was determined by nuclear magnetic resonance technology.The results show that the supercritical CO_(2)/H_(2)O mixture huff and huff can effectively enhance shale oil recovery.The soaking time has a great influence on EOR in shale cores with poor porosity and permeability.The injection pressure is closely related to the diffusion rates and flow capacity of the supercritical CO_(2)/H_(2)O mixture,and the increment of enhancing oil recovery under miscible conditions is significant.The producing ratio of oil in large pores enhances as the the huff and huff cycle increases,but it is not possible to produce more oil in small pores by increasing huff and puff cycles.