Gas hydrate formation and its accumulation potential in Mohe permafrost, China

The Mohe region is an area of continuous permafrost in northernmost China with strong similarities to other known gas-hydrate-bearing regions. Permafrost thickness is typically 20-80 m; average surface temperature ranges from -0.5 degrees C to -3.0 degrees C, and the geothermal gradient is roughly 1.6 degrees C/100 m. We estimate that 204.66 x 10(12) m(3) of hydrocarbon gases have been generated in the Mohe basin from nearly 1000 m middle Jurassic dark mudstones, providing ample gas source for gas hydrate formation. Numerous folds in the shallow section provide opportunities to trap gas within sandstones and siltstones reservoirs bounded by competent mudstone seals. Gas migration to the shallow section is enabled via fault fracture zones and fracture systems. Based on core description and observations of gas releases from drilled wells, we infer that the Mohe region could hold large quantities of natural gas in the form of gas hydrate. (C) 2012 Elsevier Ltd. All rights reserved.