关键词: 缝洞型碳酸盐岩油藏, 原油体积系数, 原油压缩系数, 幂函数, 新型油藏生产指示曲线

Abstract: The production index curve of elastic drive reservoir has always been regarded as a straight line. Because oil compressibility is a variable that decreases as formation pressure increases,the production index curve is not a straight line but a curve,which deviates from straight line more significantly as reservoir pressure drop increases. Especially for deep buried fractured-vuggy carbonate reservoirs which have large pressure difference between formation pressure and oil saturation pressure,the production index curve of reservoir will produce obvious error, hence it needs to be improved. By creating the power function relationship between oil volume factor,oil compressibility and formation pressure,the material balance equation of elastic drive fractured-vuggy carbonate reservoir was simplified,and a new production index curve of reservoir was established. The results show that the relationship between oil volume factor and formation pressure above saturation pressure is not linear but accords with power function,and the power function relationships between oil volume factor,oil compressibility and formation pressure not only conform to the actual law but also have high computational accuracy. There are two cases for using oil compressibility:one is the oil compressibility at a certain formation pressure,the other is the average oil compressibility in a certain formation pressure range,the two cases cannot be mixed,and material balance equation should adopt the latter. The new production index curve of elastic drive reservoirs is always a straight line,and the slope of the line is just original oil in place. Therefore,the new production index curve of reservoir is conducive to reservoir research,such as accurately judging the driving type of a reservoir and calculating the reserves.

Key words: fractured-vuggy carbonate reservoir, oil volume factor, oil compressibility, power function, new production index curve of reservoir