针对低渗砂岩油藏进行了CO2驱开发技术研究,分析了CO2驱油化学机理及主要影响因素.基于目标油藏流体特征进行了PVT拟合,确定其CO2驱最小混相压力,明确了不同压力及注入时机对CO2驱采收率、气油比、含水率及驱动压差等的影响规律,探究了 CO2 泡沫驱在提高采收率方面的效用.结果表明:24.5 MPa为目标区域CO2驱的最小混相压力,采收率会随着压力的升高而增加,28 MPa时CO2驱提高采收率可达 30.57%.气体突破时间、总采收率与 CO2 注入时机密切相关,CO2 注入越早,越有利于采收率的提高,出口含水率为60%时注入可提高采收率39.13%.CO2泡沫驱可以在一定程度上起到提高采收率的效用.
Research on Chemical Mechanism and Enhanced Oil Recovery of CO2 Flooding in Low Permeability Sandstone Oilfields
CO2 flooding development technology for low-permeability sandstone reservoirs was studied,the chemical mechanism and main influencing factors of CO2 flooding were analyzed.Based on the fluid characteristics of the target reservoir,PVT fitting was carried out to determine the minimum miscible pressure of CO2 flooding,and the influence laws of different pressures and injection timing on the recovery factor,gas oil ratio,water cut and driving pressure difference of CO2 flooding were clarified,and the effectiveness of CO2 foam flooding in improving recovery factor was explored.The results showed that 24.5 MPa was the minimum miscibility pressure for CO2 flooding in the target area,and the recovery rate could increase with the increase of pressure.At 28 MPa,CO2 flooding could improve the recovery rate by up to 30.57%.The gas breakthrough time and total recovery rate were closely related to the timing of CO2 injection.The earlier CO2 injection was,the more conducive it was to improving the recovery rate.The recovery rate could be increased by 39.13%when the injection was carried out at the outlet water content of 60%.CO2 foam flooding could improve oil recovery to a certain extent.
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