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| AMT forward modeling research on detecting natural gas hydrate in Muli permafrost area, Qinghai Province |
| PEI Fa-Gen1, 2, 3, FANG Hui1, 2, 3, QIU Gen-Gen1, 2, 3, HE Mei-Xing1, 2, 3, PENG Yan1, 2, 3, LYU Qin-Yin1, 2, 3 |
1. Eelectromagnetic Detection Technology Key Laboratory of Ministry of Land and Resources, Langfang 065000, China;
2.National Modern Geological Exploration Technology Research Center, Langfang 065000, China;
3. Institute of Geophysical and Geochemical Exploration, CAGS, Langfang 065000, China |
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Abstract Since the discovery of natural gas hydrate in Muli area of Qinghai Province for the first time in 2008, a series of geophysical and geochemical exploration work has been done. However, the fact that the gas hydrate reservoir in this area has features of low porosity and low permeability has brought many challenges to exploration work. To obtain the electrical response characteristics of the natural gas hydrate models in the frozen soil area, the authors conducted the AMT forward modeling of the gas hydrate in this paper. Based on the thin layer distribution characteristics of gas hydrate and the distribution range of the logging resistivity values of gas hydrate, the authors constructed two types of models, i.e., sandstone and mudstone models. Through the AMT forward modeling and inversion studies of the two models, the electrical response characteristics of the two models were obtained. The results are as follows: (1) When the ratio of the thickness of the hydrate layer to the depth of the hydrate layer and the ratio of the resistivity of the hydrate layer to the resistivity of surrounding rock meet certain conditions, both the sandstone models and the mudstone models can be used to distinguish the hydrate layer by 1D inversion curve. (2) In the hydrate stability zone of Muli area, the resistivity value of the hydrate layer is equal to 400 Ω·m or 200 Ω·m; when the ratio of the thickness of the hydrate layer to the depth of the thin hydrate layer is equal to 10%, the one-dimensional inversion can be used to distinguish the hydrate layer, and when the ratio of the thickness of the hydrate layer to the depth of the thin hydrate layer ≤5%, the one-dimensional inversion can not distinguish the hydrate layer.
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Received: 08 September 2017
Published: 20 December 2017
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