气体水合物生成实验过程动态监测:一种新的ERT方法及其效果分析

Experimental Dynamic Monitoring of Gas Hydrate Formation:A New ERT Method and Its Effectiveness Analysis

现阶段适用于天然气水合物资源开采过程获得其空间分布变化的现场监测技术仍不完善。以电阻率层析成像(ERT)技术为基础,研发一套新的ERT阵列(由两组平行的垂向电极组合而成,每组阵列有24个环形电极)应用于水合物储层动态变化监测模拟实验。通过开展物理模拟实验,采用新的ERT方法对水合物生成过程进行了动态监测,并分析了动态监测方法的应用效果。通过对实验数据统计分析,92%的数据标准偏差小于5%,证实该装置获取的电学数据资料具有较高质量。通过对高阻介质模拟实验,发现温度压力条件的变化对ERT监测结果影响较小,成像结果显示饱含3.5%NaCl溶液的沉积物电阻率约为1Ω·m与阿尔奇公式计算所得电阻率基本一致,验证了其具有较高的适用性。新的ERT方法有效地监测了水合物生成过程中电阻率变化,平均电阻率随着水合物的生成从0.95Ω·m增大至1.95Ω·m并观察到"爬壁效应",证明其在水合物监测中具有良好的应用效果,并有助于实现对水合物饱和度空间分布的动态监测。研究成果为开展实验室内水合物生成和分解过程演化研究提供了方法和技术支持,也有助于研发现场天然气水合物储层动态变化监测技术和设备。

At present,on-site monitoring techniques suitable for determining spatial changes in hydrate formation and dissociation for resource exploitation is still imperfect.The new ERT array comprises two sets of parallel vertical electrodes,each with 24 electrodes.Through conducting physical simulation experiment,the new ERT method is used to monitor the hydrate formation process,and the application effectiveness of the dynamic monitoring method is analyzed.Based on statistical analysis of the physical simulation data,the standard deviation is below 5%for 92%of the data,which supports that the experimental device can obtain high-quality electrical data.Through the simulation experiment of high-resistivity medium,it is found that temperature and pressure changes have little influence on the ERT monitoring results.The imaging results show that the sediment resistivity saturated with 3.5%NaCl solution is about 1Ω·m,which is basically equal to that calculated by the Archie’s formula.The applicability of ERT monitoring method is verified.The new ERT method effectively monitors the resistivity change in hydrate formation.The average resistivity increases from 0.95 to 1.95Ω·m with the hydrate formation,and the“climbing effect”is observed.This supports that the approach is effective in hydrate monitoring,and facilitates dynamic monitoring of the spatial hydrate-saturation distribution.The results provide experimental and theoretical support for further research on hydrate formation and dissociation in sediments,and provide reference for the development of field hydrate monitoring technology.