超临界CO2驱提高致密油藏采收率实验研究

针对玛湖地区致密油藏衰竭式开发后期采油速度快速递减的问题,提出利用超临界CO₂驱替开发致密油藏的研究思路,通过开展超临界CO₂萃取致密油实验、最小混相压力实验及长岩心驱替实验,探究了超临界CO₂驱替提高致密油采收率的作用机理、开发特征及影响因素,优选了注气速度、CO₂转注时机等重要操作参数。实验结果表明:CO₂萃取轻质组分能力随萃取次数的增加而减弱;注气速度对最终采收率影响较大,最优注气速度为0.10 cm³/min;原油与超临界CO₂最小混相压力为34.18 MPa;当前油藏压力条件为最佳CO₂转注时机。该研究成果对致密油藏高效开发具有一定指导意义。

Experimental Study on Improving Recovery Efficiency of Tight Oil Reservoirs with Supercritical Carbon Dioxide Flooding

In view of rapid decline in oil recovery rate in the late stage of natural depletion of tight oil reservoirs in the Mahu area, a study design of developing tight oil reservoirs with supercritical CO₂ displacement was put forward. The experiments on tight oil extraction with supercritical CO₂, minimum miscibility pressure and long core displacement were conducted to study the mechanism, development characteristics and influence factors of improving recovery efficiency of tight oil reservoirs with supercritical CO₂ displacement, and optimize important operating parameters such as gas injection rate and CO₂ injection occasion. The experimental results show that the capacity of light component after CO₂ extraction decreased with the increase of extraction times; the gas injection rate had a greater impact on the final recovery efficiency, and the optimal gas injection rate was 0.10 cm³/min; the minimum miscibility pressure of crude oil and supercritical CO₂ was 34.18 MPa; the current pressure in the reservoir was the best occasion for CO₂ injection. The study results play a guiding role in the efficient development of tight oil reservoirs.