确定天然气水合物饱和度的测井解释新方法

为了丰富和发展天然气水合物的定性识别方法和定量解释技术,研究试验了由测井资料计算孔隙水的氯离子质量浓度并确定水合物饱和度的方法。根据南海某海域水合物储层的测井特征和孔隙水氯离子质量浓度化验结果,证实了氯离子质量浓度与水合物饱和度有密切关系。利用孔隙度测井和电阻率测井资料,计算了孔隙水的氯离子质量浓度,由此确定了天然气水合物的饱和度。为了提高测井解释的可靠性,用回归方法建立了储层的孔隙度解释公式,确定了相应的阿尔奇参数m和a,用滤波和插值的方法得到了目的层的氯离子质量浓度的背景值。初步应用表明,由测井解释氯离子质量浓度计算的水合物饱和度与化验结果的平均值和分布范围都有较好的匹配。

A New Method for Gas Hydrate Saturation Estimation Using Well Logging Data

In order to develop and enrich the qualitative identification and quantitative interpretation methods in gas hydrate investigation,a new method for gas hydrate saturation estimation using chloride concentration from well logging interpretation was studied and applied with field data.The experimental result on chloride concentration,along with the log response of the gas reservoir in certain area in South China Sea,show the well-known close relationship between gas hydrate content and pore water’s chloride concentration.Chloride concentration of pore water was calculated through porosity and resistivity logs,and gas hydrate content was estimated from it consequently.For the purpose of improving the accuracy and reliability of this method,a regression formula for porosity interpretation was built up,the parameters of m and a in Archie formula were estimated,and the background value of chloride concentration correspond to the target zone was defined by filtering and interpolation.The preliminary application show that the method for gas hydrate content estimation by using of chloride concentration from log interpretation can work as expected and the estimated gas hydrate content can match the experimental result approximately both in their mean values and distribution ranges.