Geological structures associated with potential gas-hydrate accumulation in the Mohe permafrost, North East China.

Geological structure has become a hot research topic in gas-hydrate exploration. Until now, gas hydrate has not been found in the Mohe permafrost. Lack of information about geological structures that are closely related to the potential gas-hydrate accumulation in the permafrost, seems to be one of the limitations to the gas-hydrate exploration. In this paper, imaging logging and isotope dating are adopted to indicate that geological structures, associated with the potential gas-hydrate accumulations, including faults, fractures, and anticlines, are highly developed in the permafrost. The north-dipping normal faults and the unfilled fractures below 700 m, are considered as structure passages for the migration of hydrocarbon gas in the permafrost, while reverse faults, unfilled fractures, and anticlines of approximately 100–700 m provide the majority of reservoir spaces for the potential gas-hydrate accumulation. The area is surrounded by Luoguhe Village, Laoyeling Hill, Beihong Village, Shuangjianshan Hill, and Ershibazhan Forest Farm and is conducive for the accumulation of the potential gas-hydrate in the Mohe permafrost, because it contains the most developed permafrost and a large number of wide-space anticlines and faults. Furthermore, the depths of 300–700 m, where the unfilled high-angle fractures have been developed, are identified as the most favourable interval for the potential gas-hydrate occurrence. Therefore, it is concluded that the reverse faults, unfilled fractures, and the anticlines at the depth of 300–700 m in this area can be considered as the primary drilling objects for the gas-hydrate exploration. The importance of this study is to minimise the cost of gas-hydrate exploration drilling in the Mohe permafrost. These findings can also be used for future gas-hydrate exploration projects in similar permafrost zones. • The geological structures associated with potential gas-hydrate accumulation are highly developed in the Mohe permafrost. • The reactivations of the structures in the Cenozoic are conducive to potential gas-hydrate accumulation in the Permafrost. • The normal and reverse faults and the unfilled crevices could be passages for gas migration during the gas-hydrate formation. • The reverse faults, unfilled crevices and anticlines provided the reservoir spaces for potential gas-hydrate accumulation. • The anticlines and north-dipping faults determine the regional distributions of potential hydrate, while the reverse faults and unfilled high-angle crevices restrict its occurrence. [ABSTRACT FROM AUTHOR]