不同注入气体下低渗油藏注气开发室内评价

为了探索乌石17-2油田注气开发方式可行性以及进一步提高油田开发效果,从室内实验角度出发,对三种气体(N_2、CO_2、烃类气)开展了注气膨胀实验、细管实验、长岩心驱替实验,并进行对比分析及效果评价。研究结果表明:N_2在地层条件下表现为非混相驱,其对原油的降黏及膨胀能力有限,后期气窜明显,注气突破时间较早,突破前采出近90%左右的原油,而突破后基本为无效注气,几无产出。室内驱油效率仅为36.3%,开发效果差。烃类气、CO_2与地层原油相态配伍性要好,最小混相压力低,分别为27.52、27.13 MPa。地层条件下易形成近混相驱,气体突破要晚,气体突破以后仍能采出近30%左右的原油,驱油效率要高于非混相驱近25%,最终驱油效率分别为66.7%、69.0%,开发效果好。烃类气驱、CO_2驱可作为乌石17-2油田低渗强水敏储层优选能量补充方式。

Laboratory Evaluation of Gas Injection in Low Permeability Reservoirs with Different Gas

In order to explore the feasibility of gas injection mode in WS17-2 oilfield and further improve the development effect of oilfield, gas injection expansion experiment, slim tube experiment and long core displacement experiment were carried out for three kinds of gases (N2, CO2, hydrocarbon gas), and the comparative analysis and effect evaluation were also carried out. The results show that N2 is immiscible flooding under formation conditions, and its ability to reduce viscosity and expand crude oil is limited. Gas channeling is obvious in the later stage. Gas injection breakthrough time is early. Nearly 90% of crude oil is produced before breakthrough, and after breakthrough, it is basically ineffective gas injection, with little output. Indoor oil displacement efficiency is only 36.3%, the development effect is poor. The compatibility of hydrocarbon gas and CO2 with formation crude oil is good, and the minimum miscibility pressure is 27.52 MPa and 27.13 MPa, respectively. Near miscible flooding is easy to form under formation conditions. Gas breakthrough is late. After gas breakthrough, about 30% of crude oil can still be produced. Oil displacement efficiency is higher than that of immiscible flooding by nearly 25%. The final oil displacement efficiency is 66.7% and 69.0%, respectively. The development effect is good. Hydrocarbon gas flooding and CO2 flooding can be used as energy supplement for WS17-2 Oilfield low permeability and strong water sensitive reservoirs.