The manifestation of subaqueous gas hydrate formations in the electromagnetic transient

Abstract

Introduction: the detection of gas hydrate (GH) accumulations is an important task both as a useful mineral and as an unstable component of the technosphere. Gas reserves in the gas hydrate state are quite large and exceed its reserves in a free state, which, along with the estimated volumes of world reserves, makes gas hydrates one of the most promising types of energy resources. An obvious advantage of gas hydrate deposits is also their shallow occurrence depths (in comparison with traditional gas) and their widespread distribution in the near-surface layers of the lithosphere, including in water areas;

Methodology: the study is based on a numerical experiment – a comparison of the results of solving the electromagnetic (EM) direct problem for a normal and anomalous one-dimensional conducting polarizing geoelectric model;

Results and discussion: geoelectric models of subaquatic GH clusters for freshwater and marine conditions are proposed, calculations of the EM signal are made on electrical installations of different sizes. Based on the difference between the anomalous and normal signals and their discrepancy, conclusions are made about the manifestation of an anomalous object;

Conclusion: the study of the anomalous effect of GH showed the possibility of their detection by electrical installations. In a freshwater reservoir, a polarization signal associated with a gas hydrate layer appears in the transient process. For marine conditions, the presence of GH is more contrasting when it reaches the seabed; when an overlying layer of permafrost appears, the anomalous effect decreases, especially strongly for installations with a short source length. Generally, the studied object is contrastingly manifested in measurements by electrical lines. A large share of the anomalous effect is associated with the contrast of the object in terms of resistivity and appears during the early stage of the transient (EST). The anomalous effect associated with polarization properties (at a late stage of formation) appears on smaller installations, but in terms of the amplitude of the discrepancy it is inferior to the anomalous effect during the EST.