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

doi:10.19657/j.geoscience.1000-8527.2021.103

Abstract

Abstract:

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 1 Ω·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 1.95 Ω·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.

Key words: gas hydrate, electrical resistivity tomography, physical experiment simulation, dynamic monitoring

CLC Number:

P631.8

LIU Yang, CHEN Qiang, ZOU Changchun, ZHAO Jinhuan, PENG Cheng, SUN Jianye, LIU Changling, WU Caowei. Experimental Dynamic Monitoring of Gas Hydrate Formation: A New ERT Method and Its Effectiveness Analysis[J]. Geoscience, 2022, 36(01): 193-201.

Figures/Tables 8

Fig.1 Hydrate reservoir dynamic monitoring simulation experimental device based on electrical resistivity tomography

Fig.2 Electrode layout and acquisition modes of old ((a) modified after ref.[23]) and new (b) ERT array

Table 1 Repeated measurement experiment parameters

模型序号	介质	溶液浓度/%	温度	压力	采集次数
1	NaCl溶液	0.12	常温	常压	10
2	天然海沙、NaCl溶液	3.50	常温	常压	10

Fig.3 Statistical graphs of the standard deviation of the measured data of the two models

Table 2 Physical experiment simulation parameters

实验编号	介质	温度 T/℃	压力 P/MPa
1	3.5% NaCl溶液、沉积物、1个高阻介质	23	0.1
2	3.5% NaCl溶液、沉积物、1个高阻介质	23	8.0
3	3.5% NaCl溶液、沉积物、1个高阻介质	0	8.0

Fig.4 Imaging results of high resistivity body simulation experiments in different environments (P is pressure; T is temperature)

Fig.5 Temperature and pressure curves during hydrate formation

Fig.6 Resistivity distribution during hydrate formation (R is the average resistivity; t is time)

References 28

[1]	SLOAN D E. Fundamental principles and applications of natural gas hydrate[J]. Nature, 2003, 426: 353-363. DOI URL
[2]	COLLETT T S. Energy resource potential of natural gas hydrates[J]. AAPG Bulletin, 2002, 86(11): 1971-1992.
[3]	KVALSTAD T J, ANDRESEN L, FORSBERG C F, et al. The Storegga slide: evaluation of triggering sources and side mechanics[J]. Scientific Journal of Earth Science, 2014, 4(3): 146-155.
[4]	HOVLAND M, GUDMESTAD O T. Potential influence of gas hydrates on seabed installations[M]// American Geological Union.Natural Gas Hydrates:Occurrence, Distribution, and Detection. Washington: American Geological Union, 2001: 307-315.
[5]	SULTAN N, COCHONAT P, FOUCHER J P, et al. Effect of gas hydrates melting on seafloor slope instability[J]. Marine Geology, 2004, 213(1): 379-401. DOI URL
[6]	沈平, 强建科, 李永军, 等. 井间视电阻率的几何成像方法[J]. 中南大学学报(自然科学版), 2010, 41(3):1079-1084.
[7]	HAARDER E B, BINLEY A, LOOMS M C, et al. Comparing plume characteristics inferred from cross-borehole geophysical data[J]. Vadose Zone Journal, 2012, 11(4): 1539-1663.
[8]	邵帅, 吴景鑫, 郭秀军, 等. 储油区泄漏电学实时监测系统设计与应用效果分析[J]. 地球物理学进展, 2020, 35(2): 1-11.
[9]	马凤山, 底青云, 李克蓬, 等. 高密度电阻率法在海底金矿含水构造探测中的应用[J]. 地球物理学报, 2016, 59(12): 4432-4438.
[10]	苏永军, 马震, 孟利山, 等. 高密度电阻率法和激发极化法在抗旱找水定井位中的应用[J]. 现代地质, 2015, 29(2): 265-271.
[11]	孟庆国, 刘昌岭, 业渝光, 等. 不同类型天然气水合物真空分解过程实验[J]. 现代地质, 2010, 24(3): 607-613.
[12]	贾佳林, 张郁, 李刚, 等. 南海海泥中甲烷水合物生成特性的实验研究[J]. 现代地质, 2013, 27(6): 1373-1378.
[13]	陈强, 业渝广, 刘昌岭, 等. 多孔介质中甲烷水合物相变过程模拟实验研究[J]. 现代地质, 2010, 24(5): 972-978.
[14]	胡高伟, 业渝光, 张剑, 等. 松散沉积物中天然气水合物生成、分解过程与声学特性的实验研究[J]. 现代地质, 2008, 22(3): 465-474.
[15]	LI S X, XIA X R, XUAN J, et al. Resistivity in formation and decomposition of natural gas hydrate in porous medium[J]. Chinese Journal of Chemical Engineering, 2010, 18(1): 39-42. DOI URL
[16]	STOLL R D, BRYAN G M. Physical properties of sediments containing gas hydrates[J]. Journal of Geophysical Research: Solid Earth, 2012, 84(4):10-15.
[17]	陈强, 刘昌岭, 邢兰昌, 等. 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[J]. 石油学报, 2016, 37(2): 222-229.
[18]	李淑霞, 夏唏冉, 郝永卯, 等. 电阻率测试技术在沉积物-盐水-甲烷水合物体系中的应用[J]. 实验力学, 2010, 25(1): 95-99.
[19]	SPANGENBERG E, PRIEGNITZ M, HEESCHEN K, et al. Are Laboratory-formed hydrate-bearing systems analogous to those in nature?[J]. Journal of Chemical and Engineering Data, 2014, 60(2): 258-268. DOI URL
[20]	PRIEGNITZ M, THALER J, SPANGENBERG E, et al. Characterizing electrical properties and permeability changes of hydrate bearing sediments using ERT data[J]. Geophysical Journal International, 2015, 202(3): 1599-1612. DOI URL
[21]	赵洪伟, 刁少波, 业渝光, 等. 多孔介质中水合物阻抗探测技术[J]. 海洋地质与第四纪地质, 2005, 25(1): 137-142.
[22]	李小森, 冯景春, 李刚, 等. 电阻率在天然气水合物三维生成及开采过程中的变化特性模拟实验[J]. 天然气工业, 2013, 33(7): 18-23.
[23]	PRIEGNITZ M, THALER J, SPANGENBERG E, et al. A cylindrical electrical resistivity tomography array for three-dimensional monitoring of hydrate formation and dissociation[J]. The Review of Scientific Instruments, 2013, 84(10): 104502. DOI URL
[24]	WALSH M. Laboratory and high-pressure flow loop investigation of gas hydrate formation and distribution using electrical tomography[M]//ICGH. Proceedings of the 8th International Conference on Gas Hydrates. Beijing: ICGH, 2014:8.
[25]	HEESCHEN K U, ABENDROTH S, PRIEGNITZ M, et al. Gas production from methane hydrate: a laboratory simulation of the multistage depressurization test in Mallik, Northwest Territories, Canada[J]. Energy and Fuels, 2016, 30(8): 6210-6219. DOI URL
[26]	李彦龙, 孙海亮, 孟庆国, 等. 沉积物中天然气水合物生成过程的二维电阻层析成像观测[J]. 天然气工业, 2019, 10(1): 132-138.
[27]	WU N Y, LIU C L, HAO X L. Experimental simulations and methods for natural gas hydrate analysis in china[J]. China Geology, 2018, 1(1): 61-71. DOI URL
[28]	YANG X, SUN C Y, SU K H, et al. A Three-dimensional study on the formation and dissociation of methane hydrate in porous sediment by depressurization[J]. Energy Conversion and Ma-nagement, 2012, 56: 1-7.