地层水矿化度对含水饱和度精度的影响分析

精确确定地层混合液电阻率和阿尔奇参数是剩余油饱和度评价的核心技术,但是在注水开发过程中地层混合液电阻率是动态变化的,同时当地层水矿化度变化较大时,胶结指数m和饱和度指数n随地层水矿化度的增大而增大,影响了由阿尔奇公式确定的含水饱和度的计算精度。提出首先采用变倍数物质平衡法得到地层混合液电阻率,再利用W-S模型和阿尔奇公式建立动态m、n值计算公式,在求准一系列地质参数的基础上再进行含水饱和度的计算。结果表明:采用变倍数物质平衡法能够得到精度较高的混合液电阻率;采用随地层水矿化度变化的m、n值能够显著提高含水饱和度的计算精度。

Analysis for effect of variable formation water salinity on accuracy of water saturation

Determining the formation resistivity of mixed fluid and the Archie ''s parameters precisely is the core technique for the evaluation of remaining oil saturation. During the water-flooding development, the formation resistivity of mixed fluid is however a dynamic parameter. In addition, when the water salinity varies in a wide range, the cementation exponent (m) and the saturation exponent (n) increase with increasing water salinity, affecting the accuracy in calculating water saturation using the Archie formula. In this paper, a method to obtain high-precision formation resistivity of mixed fluid is proposed using the theoretical simulation material balance method of variable multiple injected water. Based on the W-S model and Archie ''s formula, the formulas to calculate the dynamic cementation exponent (m) and saturation exponent (n) are derived, that potentially provides a series of geologic parameters for the calculation of water saturation. The study shows that the method can improve the accuracy of the resistivity of mixed liquid; and using dynamic values of the m and n can improve the accuracy of water saturation significantly.