CO2与压裂地层置换规律实验研究

针对致密油藏注不进,采不出的开发难题和低产量、低效益的开发现实,基于国外对致密油藏CO2驱的成功案例,提出了CO2干法压裂以及CO2置换相结合的开发思路。模拟干法压裂地层,开展了CO2置换实验,研究了焖井时间、焖井压力、返排压差等因素对CO2置换效率的影响。并借助CT扫描技术,对比实验前后岩心内流体的分布推测置换实验反应情况。实验结果表明：最佳焖井时间为12~24 h；焖井压力大于最小混相压力(20.56 MPa)时焖井后能取得较高置换效率；返排压差在6 MPa以上开发效果最佳。在压裂的致密油藏内,离裂缝距离中等的岩心部位置换效果最好,其次为靠近裂缝的岩心部位,而距裂缝最远的岩心部位置换效果最差。

Experimental study on displacement law of CO2 and fractured formation

In view of the development problems of tight reservoir that can not be injected and produced, and the development reality of low production and low benefit. Based on the successful cases of CO2 flooding in tight reservoirs abroad, the development ideas of CO2 dry fracturing and CO2 replacement are put forward. Simulated dry fracturing formation, carried out CO2 replacement experiment, studied the effect of soak time, soak pressure, backflow pressure difference and other factors on CO2 replacement efficiency. With the help of CT scanning technology, the fluid distribution in the core before and after the experiment was compared to predict the reaction of displacement experiment. The experimental results show that the best soaking time is 12-24 h; when the soaking pressure is more than the minimum miscible pressure (20.56 Mpa), the replacement efficiency is higher; the development effect is the best when the backflow pressure difference is more than 6 Mpa. In the fractured tight reservoir, the replacement effect of the core part with the middle distance from the fracture is the best, followed by the core part close to the fracture, and the core part with the farthest distance from the fracture is the worst.