孔隙水垂向不均匀分布体系中水合物生成过程的电阻率变化

Resistivity variation during hydrate formation in vertical inhomogeneous distribution system of pore water

天然气水合物具有极强的储气能力,被认为是一种潜力巨大的新型能源矿产。电阻率测井技术在海洋天然气水合物勘探工作中发挥着重要作用,然而涉及水合物电阻率数据的处理与Archie公式应用等方面的工作仍需进一步完善。利用自主研发的水合物电学特性模拟实验装置开展了孔隙水垂向不均匀分布体系中甲烷水合物的合成实验,获得了不同饱和度下含水合物沉积物电阻率数据,并在此基础上试算了Archie公式的经验参数。结果表明:电阻率变化能够指示水合物反应过程,其变化特征是反应不同阶段排盐效应、孔隙含水量和孔隙填充方式等多种影响因素共同作用的结果;含水合物的天然海砂电阻率参数存在非Archie现象,地层因子、电阻率增大指数等Archie公式参数受水合物饱和度变化的影响。

Because of its extremely strong gas storage capacity,natural gas hydrate is considered to be a new kind of energy mineral resource with huge potential.The resistivity logging technology plays an important role in the exploration of marine natural gas hydrate.However,the processing of resistivity data,the application of Archie equation and other aspects require further improvement.In this study,the synthesis experiments of methane hydrates in the vertical inhomogeneous distribution system of pore water were carried out based on the independently-developed simulating experimental device with hydrate electrical properties,so as to obtain the resistivity data of hydrate-bearing sediments under different saturations.On this basis,the empirical parameters of Archie equation were calculated accordingly.The results reveal that the resistivity variation is capable to indicate the hydrate reaction process,and the related changing characteristics are resulted from the joint reaction of multiple influence factors,such as salt-removing effect,pore water content and pore-filling pattern during different stages.Non-Archie phenomena have been discovered in the resistivity of hydrate-bearing natural sea sand,while the parameters of Archie equation such as formation factor and resistivity enlargement index are affected by the variation in hydrate saturation.