基于电阻率测井的天然气水合物饱和度估算及估算精度分析

利用电阻率测井基于阿尔奇公式能够估算孔隙空间中天然气水合物饱和度。基于神狐海域的水合物钻井(SH2站位)资料,利用密度反演的地层孔隙度与地层因子交会图,计算出估算水合物饱和度的阿尔奇常数。假定地层中水合物呈均匀分布,利用电阻率资料计算的该站位水合物饱和度平均为24%,最高达44%,水合物饱和度在垂向上具有明显的不均匀性;利用孔隙水氯离子异常估算的SH2站位水合物饱和度平均值为25%,最高值达48%,厚度为25 m。这两种方法估算的水合物饱和度基本吻合,利用电阻率资料计算的饱和度与阿尔奇常数和饱和度指数及孔隙度有关。

Estimation of Gas Hydrate Saturation Based on Resistivity Logging and Analysis of Estimation Error

Gas hydrate saturations can be estimated from the Archie equation and the estimation error is dependent on the porosity,saturation factor and Archie's parameters.From the crossplot between density porosity and formation factor of site SH2 in Shenhu area,the Archie parameters were calculated based on the water-saturated sediments.Gas hydrate saturation estimated from isotropic resistivity has an average value of 24% with a maximum value of 44%.The distribution of gas hydrate is heterogeneous in vertical.Chloride anomalies in the core samples show that the average saturation is about 25% in the pore space with a maximum value of 48%,and the thickness of gas hydrate is about 25 meters.The results show that gas hydrate saturations estimated from resistivity data by using the environment parameters in Shenhua area are similar to those estimated from chloride anomalies.The value of gas hydrate saturation estimated from resistivity data depends on the parameters of Archie parameters and the gas hydrate exponents.