广义气水混驱特征曲线的建立及应用

Establishment and Application of Generalized Characteristic Curves of Gas⁃Water Miscible Flooding

为解决目前气水混驱特征曲线评价油藏开发效果方法较少的问题,引入了地下含气水率,并类比水驱油藏含水变化规律广义数学模型,建立了广义气水混驱特征曲线及其对应的广义含气水变化规律数学模型。新的广义气水混驱特征曲线在n=0和m=0时,为甲型气水交替驱特征曲线;在n=1和m=0时,则为乙型气水交替驱特征曲线。n和m取不同数值时,广义气水混驱特征曲线可以转化为S型气水混驱特征曲线,也可以转化为凸型、S-凸型、S-凹型、凹型等气水混驱特征曲线。为了便于矿场应用,给出了气水混驱特征曲线通式及其对应的含气水变化规律数学模型的求解方法,并应用于葡北油田三间房组油藏气水交替驱和锦州油田S31油藏气顶气+边水驱开发效果的评价,拟合精度较高,可供其他油藏借鉴。

Considering the limited methods for evaluating reservoir development performance using gas-water miscible flooding characteris-tic curves,a concept of underground water-gas cut was introduced.By analogy with the generalized mathematical model of water cut varia-tion in water flooding reservoirs,generalized gas-water miscible flooding characteristic curves and the corresponding generalized mathemati-cal models of underground gas-water cut variation were established.The generalized gas-water miscible flooding characteristic curve is a Type A water-alternating-gas(WAG)injection characteristic curve when n=0 and m=0,and a Type B WAG injection characteristic curve when n=1 and m=0.By varying the values of n and m,the generalized gas-water miscible flooding characteristic curve can be transformed into S-shaped,convex,S-convex,S-concave,and concave gas-water miscible flooding characteristic curves.For purpose of field application,a general formula for the generalized gas-water miscible flooding characteristic curve and solution method for the corresponding mathemati-cal model combining underground gas-water cut variation were provided.The application to the evaluation of the development performance of WAG injection in the reservoir of Sanjianfang formation in Pubei oilfield,and of gas cap gas+edge water displacement in S31 reservoir in Jinzhou oilfield shows a high fitting accuracy.This method can be a reference for other reservoirs.