低渗透砂砾岩油藏二氧化碳驱提高采收率

EOR of CO_(2) Flooding in Low-Permeability Sandy Conglomerate Reservoirs

焉耆盆地本布图油田低渗透砂砾岩油藏早期采用注水开发,储集层伤害严重,注水困难,采出程度低,亟需开展转换注驱研究,进一步提高采收率。为确定本布图油田低渗透砂砾岩油藏注CO_(2)提高采收率的可行性,开展了室内实验研究。结果表明,研究区地层原油膨胀性好,易降黏,易混相;最小混相压力为25 MPa,在目前地层压力下可达到近混相驱,驱油效率较高,具有大幅提高采收率的潜力。利用数值模拟对CO_(2)驱开发技术进行优化设计,采用五点法井网,连续注气开发,预计提高采收率13.37%,CO_(2)换油率0.330 t/t,为下一步矿场试验提供了理论依据。

The low-permeability sandy conglomerate reservoirs of Benbutu oilfield in Yanqi basin was developed by water flooding in the early stage.While along with water flooding,the reservoirs were seriously damaged,it was even harder to inject water into the reservoirs and the recovery rate stayed in a low level,therefore,it is urgent to switch flooding agent to further improve the recovery rate.In order to determine the feasibility of CO_(2) injection in the low-permeability sandy conglomerate reservoirs in Benbutu oilfield to enhance oil recovery,indoor experimental researches were carried out.The research results show that the crude oil in the formation of the study area has good swellability,is easily miscible with the injected CO_(2),and the viscosity of the crude oil is easy to be reduced.The minimum miscible pressure of the reservoirs is about 25 MPa,and near-miscible flooding can be achieved under the current formation pressure.The oil displacement efficiency of CO_(2) flooding is relatively high,which can dramatically improve recovery rate.The CO_(2) flooding plan was optimized with numerical simulation,in which a five-spot well pattern and a continuous gas injection method were adopted,and the oil recovery is expected to increase by about 13.37%and the oil diplacement ratio of CO_(2) injection will be about 0.33 t/t.The numerical simulation results provide a theoretical basis for the next field application.