延长油田南部长8致密油藏注CO_(2)吞吐实验

Experiment of CO_(2) huff and puff in Chang8 tight oil reservoir,south of Yanchang Oilfield

为探究致密油藏注气吞吐提高采收率影响因素,以延长油田南部长8致密储层为对象,开展了长岩心注CO_(2)吞吐实验,研究了注气速度、焖井时间、压力衰减速度、吞吐周期等对注气吞吐采出程度的影响。实验表明:(1)压力衰减速度是影响注气吞吐的主要因素,压力衰减速度越大,采出程度越低,下降幅度达4.1%,考虑生产实际尽量保证较低压力衰减速度;(2)注气速度对注气吞吐过程影响较小,注气吞吐存在合理焖井时间,超过合理焖井时间采出程度难以大幅提高;(3)随吞吐周期轮次的增加,总采出程度逐渐增加,但单周期采出程度呈大幅降低,即第1个周期采出程度占总采出程度的70%;(4)相同条件下,注CO_(2)吞吐效果明显优于注水吞吐,采出程度平均高出2.17百分点。该研究成果对南部致密油高效补充能量开发提供理论指导。

By experiment of CO_(2) huff and puff of long core samples from Chang8 tight oil reservoir in south of Yanchang Oilfield,the effects of gas injection rate,soaking time,pressure attenuation rate,huff and puff period on CO_(2) huff and puff recovery were studied for the influencing factors.The experiments show that:(1)The pressure decay rate is the main factor affecting CO_(2) huff and puff recovery.The higher the pressure decay rate is,the lower the recovery is,with the decline of 4.1%.In field practice,the low pressure decay rate should be kept as far as possible considering the actual production.(2)There is a reasonable soaking time in CO_(2) huff and puff,beyond which it is difficult to improve recovery significantly.Gas injection rate has little influence on the gas injection huff and puff.(3)With the increase of cycles of huff and puff,the cumulative recovery gradually increases,but the recovery of single cycle huff and puff gradually decreases,that is,the recovery of first huff and puff accounts for 70%of the cumulative recovery.(4)Under the same conditions,the effect of CO_(2) injection huff and puff is obviously better than that of water injection huff and puff,and the average recovery rate is 2.17 percentage points higher.The research results provide theoretical guidance for the efficient supplementary energy development of tight oil in the south.