Permafrost and Gas Hydrate Stability Zone of the Glacial Part of the East-Siberian Shelf

Abstract

By using thermal mathematical modeling for the time range of 200–0 thousand years ago, the authors have been studying the role the glaciation, covered the De Long Islands and partly the Anjou Islands at the end of Middle Neopleistocene, played in the formation of permafrost and gas hydrates stability zone. For the modeling purpose, we used actual geological borehole cross-sections from the New Siberia Island. The modeling was conducted at geothermal flux densities of 50, 60, and 75 mW/m2 for glacial and extraglacial conditions. Based on the modeling results, the glaciated area is characterized by permafrost thickness of 150–200 m lower than under extraglacial conditions. The lower boundary of the gas hydrate stability zone in the glacial area at 50–60 mW/m2 is located 300 m higher than the same under extraglacial conditions. At 75 mW/m2 in the area of 20–40 m isobaths, open taliks are formed, and the gas hydrate stability zone was destroyed in the middle of the Holocene. The specified conditions and events were being formed in the course of the historical development of the glacial area with a predominance of the marine conditions peculiar to it from the middle of the Middle Neopleistocene.

Theoretical Prediction of the Occurrence of Gas Hydrate Stability Zones: A Case Study of the Mohe Basin, Northeast China

“…Ultimately, drilling activities aimed at hydrate discovery have shown that source rocks in the Mohe Formation in the Mohe Basin have mostly advanced to the late oil-maturity stages. , Meanwhile, it has been proven that the dominant hydrocarbon products of such a thermal evolution of both source rocks and coal-bearing formations is gas condensate, which serves as the favorable source for hydrate formation. The gas can be supplied sufficiently in the peripheries of coal mines or primary oil and gas reservoirs, potentially leading to the creation of suitable intervals of potential hydrate-bearing zones in the Mohe Basin.…”

Numerical modeling of methane hydrates dissociation in the submarine permafrost

“…The distribution of thermal conductivity and heat capacity of the frozen and thawed rocks with depth remains constant during the simulation of the permafrost evolution. Thermal conductivity and heat capacity correspond to the values in the region sedimentary basin [19].…”

“…Hydrates are formed at low temperatures and generally high pressures which are typical of relatively shallow depths in oceanic sediments or deeper frozen sediments in the Arctic [8][9][10][11]. Temperature increase [12][13][14][15][16][17] or pressure drop (sea-level drop, glacier collapse) [18][19][20] is effective enough to dissociate hydrate deposits, as a result, methane is released from the hydrate structure and may enter the atmosphere.…”

Subsea Methane Hydrates: Origin and Monitoring of Impact of Global Warming

“…• availability of data on the geological structure, as well as geothermal observations up to a depth of 200 m [9]; • increased methane emissions in this area recorded, both according to shipborne and satellite measurements [35]. To establish the geological structure and thermophysical properties of deposits we used data on the geological structure of the New Siberian Islands [9], fig. 1.…”