Effective anomaly for gas hydrate detection with marine CSEM method
Pei Jianxin1,2, Wang Qi1, Zhang Xiuli1
1. College of Marine Geosciences, Ocean University of China, Qingdao, Shandong 266100, China;
2. Key Laboratory of Submarine Science and Prospecting Techniques, Ministry of Education, Qingdao, Shandong 266100, China
Abstract：Since seabed strata electric properties are very sensitive to marine CSEM response, gas hydrate reservoirs distribution might be detected using different marine CSEM responses between reservoir and its country rocks. We calculate CSEM responses and effective anomaly, and obtain the relationship between effective anomaly, frequency and transmitter-receiver offsets based on 1D gas hydrate model. Model studies show that the effective anomaly can be used to determine suitable transmitting frequencies. Both the normalized amplitude ratio and the phase difference can be calculated on the transmitting frequencies. Gas hydrate reservoirs could be predicted based on the sensitivity of seabed strata resistivity to the effective anomaly. Model calculations demonstrate the feasibility gas hydrate reservoir characterization with marine CSEM methods.
McConnell D R, Zhang Z, Boswell R. Review of progress in evaluating gas hydrate drilling hazards. Marine and Petroleum Geology, 2012,34:209-223.
[2]
Smith S L and Judge A S. Estimates of methane hydrate volumes in the Beaufort-Mackenzie region, Northwest Territories, in Current Research, 1995-B.Geological Survey of Canada, 1995,81-88 (also Geological Survey of Canada Open File 2746, 1993).
Shi Dou, Zheng Junwei. The status and prospect of research and exploitation of natural gas hydrate in the world. Advance Earth Sciences,1999,14(4):330-338.
[5]
Boswell R, Collett T S, Frye M et al. Shelander subsurface gas hydrates in the northern Gulf of Mexico. Marine and Petroleum Geology, 2012a,34:4-30.
[6]
Shedd W, Boswell R, Frye M et al. Occurrence and nature of “bottom simulating reflectors” in the northern Gulf of Mexico. Marine and Petroleum Geology, 2012,34:31-40.
Shen Jinsong, Chen Xiaohong. Development and enlightenment of controlled-source eletromagnetic (CSEM) surveying method in marine oil/gas exploration. OGP,2009, 44(1): 119-127.
[8]
Li Yuguo and Key Kerry.2D marine controlled-source electromagnetic modeling: Part 1: An adaptive finite-element algorithm. Geophysics, 2007,72(2): WA51-WA62.
Shen Jinsong, Sun Wenbo. Numerical simulation of marine controlled electromagnetic (MCSEM) response to 2-D seabed formation.GPP, 2009,48(2): 187-194.
[10]
刘长胜, 海底可控源电磁探测数值模拟与实验研究[博士学位论文]. 吉林长春:吉林大学, 2009.
Liu Changsheng. Numerical Modeling and Experiment Study of Sea-floor Controlled-source Electromagnetic Detection[D]. Jilin University, Changchun, Jilin, 2009.
[11]
Constable S and Weiss J C. Mapping thin resistors and hydrocarbons with marine EM methods: Insights from 1D modeling. Geophysics, 2006,71(2): G43-G51.
[12]
Zhao Luanxiao, Geng Jianhua, Zhang Shengye et al. 1-D controlled source electromagnetic forward modeling for marine gas hydrates studies.Applied Geophysics, 2008,5(2): 121-126.
[13]
Karen A W. Marine Electromagnetic Methods for Gas Hydrate Characterization[D]. San Diego: University of California, 2008.
[14]
Vanessa Brown, Mike Hoversten, Kerry Key et al.Resolution of reservoir scale electrical anisotropy from marine CSEM data. Geophysics, 2012,77(2): E147-E158.
[15]
何展翔,孙卫斌,孔繁恕等. 海洋电磁法. 石油地球物理勘探,2006,41(4):451-457.
He Zhanxiang, Sun Weibin, Kong Fanshu et al. Marine electromagnetic approach. OGP,2006,41(4): 451-457.
