玛湖百口泉组致密砾岩储层天然气驱特征的实验研究

天然气驱在致密储层中具有良好的提高采收率效果,但目前尚缺乏在致密砾岩储层中的应用经验。本文选取了M131及M18井区的储层岩心,开展了长岩心天然气驱及天然气-水交替驱替实验,分析了两种注入条件下的采收率、驱替压力及出口气油比变化特征,探究了天然气驱在玛湖百口泉组致密砾岩储层中的适用性。结果表明：天然气驱在M18及M131井区致密砾岩储层提采效果显著,非混相条件下能将综合采收率提高至60%以上,而混相条件下采收率可以进一步提高至70%以上。气窜现象会显著制约储层整体的采收率,天然气-水交替注入可有效减缓储层中的气窜现象,进一步提高储层的采收率。但天然气-水交替注入会逐步提高注入压力,且注入压力会随着注入轮次的增加而提高,但混相条件下的注入压力要小得多。综合注入压力、采收率等参数,玛湖百口泉组致密砾岩储层更适宜采用混相条件下的天然气-水多轮次驱替方式来提高储层的综合采收率。

Experimental investigation on the natural gas flooding characteristics of Baikouquan formation in Mahu tight conglomerate reservoir

Natural gas flooding can significantly increase the oil recovery in tight formation, but their application in tight conglomerate reservoir is still inexperienced. In this paper, core samples were collected from bottom holes in M131 and M18 block, and natural gas flooding and alternate gas-water displacement experiments were conducted on these core samples. The oil recovery rate, displacement pressure and gas/oil ratio were recorded and the feasibility of natural gas flooding in tight conglomerate reservoir was discussed. The results shows that natural flooding can significantly increase oil recovery in M18 and M131 block. The oil recovery rate can reach 60% under immiscible condition, and under miscible condition, the oil recovery can reach above 70%. The gas channeling significantly limited the overall oil recovery rate of the formation. Water and alternate gas and water flooding can retard the gas channeling and further increase the oil recovery rate. However, it also increased the injecting pressure, and the injection pressure will increase with the increase of injection rounds. And the injection pressure under miscible condition was much lower. Considering the injection pressure, recovery rate and other parameters, it is more suitable to adopt alternate gas-water multi-cycle flooding under miscible condition in Baikouquan Formation.