不同气体对注烃气混相驱油效果的影响

Effects of different gases on hydrocarbon miscible displacements

针对国外W油田异常高压和烃气产出量不足的特点,研究了N2、CH4、CO2和烟道气等四种气体对烃气混相驱油效果的影响.利用基于混合单元网格法编制的软件,得出了四种气体与烃气驱最小混相压力的相互关系;在PVT数据拟合的基础上,运用数值模拟软件模拟注气膨胀试验得到了分别加入四种气体的烃气与原油物性的关系;在国外W油田地质模型和井组的基础上优化研究了不同注入气比例对采出程度和累计注入气量的影响.结果表明,N2、CH4和烟道气等三种气体都能不同程度地增大原油的烃气驱最小混相压力,且N2对最小混相压力的影响最大,CO2能够使得原油的最小混相压力发生微弱地降低;在储层原始压力77.59 MPa下,分别加入了四种气体的烃气都能使得原油体积膨胀系数和原油饱和压力上升,而原油的密度和粘度降低,其中N2的降粘效果和使原油膨胀的能力最强;运用数值模拟优化研究得到最优加入气为烟道气,其相应的最佳注入气比例为1.2.

The foreign W oilfield is an abnormal high pressure reservoir ,and its gas production is insufficient .In this paper ,we study the effects of the four kinds of gases ,including N2 , CH4 ,CO2 ,and flue gases ,on hydrocarbon miscible displacements .The software based on multiple mixing‐cell method is used to calculate the MMP （minimum miscible pressure） and the relationship between make‐up gas and MMP is obtained .Base on PVT data ,eclipse is used to simulate the gas‐injection expansion experiment to analyze the effects of different ga‐ses on hydrocarbon miscible displacements .Optimization is conducted to get the effects of hydrocarbon injected rate to the recovery rate and cumulative injection volume .The results show that the N2 ,CH4 and flue gases can increase the MMP of hydrocarbon displacement , and the N2 has the greatest impact on MMP ,and CO2 can make the MMP decreases .Under the initial reservoir pressure 77 .59 MPa ,the hydrocarbon gas compounded with different ga‐ses can make the oil volume and saturation pressure increase .They also can make the oil den‐sity and the viscosity decrease .Further ,N2 has the best ability to reduce oil viscosity and make the volume of crude oil expand .It is also found that flue gas is the best additive gas and the optimal injection rate is 1 .2 .