低渗透油藏CO2非混相驱替特征曲线研究

摘要

目前普遍沿用水驱特征曲线对气驱特征进行描述,尚未形成标准的气驱特征曲线及数学描述方法.针对低渗透油藏CO2非混相驱替特征,通过理论推导,建立累积产气量与累积产油量的分段关系式,形成适用于低渗透油藏CO2非混相驱的气驱特征曲线.结合室内实验和矿场生产数据分析,验证累积产气量与累积产油量呈双对数分段线性关系,表明气驱特征曲线能够较好地描述CO2非混相驱替特征.通过拟合可确定分段关系式中的常数,能够有效预测CO2非混相驱油效果.另外,应用气驱特征曲线还能够确定气窜发生的时机,并对CO2非混相驱调整措施的有效性进行快速判断.腰英台油田低渗透油藏CO2非混相驱矿场试验结果表明,CO2注入12个月后,气窜发生.根据气驱特征曲线,实施水气交替注入,气窜段斜率显著下降,气窜受到一定抑制.%The displacement characteristic curve of water drive is still used in COs immiscible flooding.There are not standard displacement characteristic curve and mathematic description method for gas drive.Piecewise relations were theoretically derived to determine the relationship between cumulative gas production and cumulative oil production.Based on displacement characteristics,the displacement characteristic curve of CO2 immiscible flooding for low permeability reservoir was obtained.Combined with laboratory experiments and pilot tests,the double logarithmic piecewise linear relations were proved effective to explain displacement characteristics of CO2 immiscible flooding.The constants of the linear relations can be regressed through production data.And they can also be used to predict the effects of CO2 immiscible flooding.Additionally,gas channeling time can be obtained by the gas displacement characteristic curve.The adjustment measures can be determined quickly through the relations.Pilot tests of CO2 immiscible flooding in Yaoyingtai Oilfield show that the gas channeling happened 12 months after gas injection.According to the gas displacement characteristic curve,the slope of gas channeling section decreased sharply after WAG applied.And the extent of gas channeling was reduced.