Assessing the permafrost temperature and thickness conditions favorable for the occurrence of gas hydrate in the Qinghai-Tibet Plateau

Permafrost accounts for about 52% of the total area of the Qinghai-Tibet Plateau. and the permafrost area is about 140 x 10(4) km(2). The mean annual ground temperature of permafrost ranges from -0 1 to -5 degrees C, and lower than -5 degrees C at extreme high-mountains. Permafrost thickness ranges from 10 to 139.4 in by borehole data, and more than 200 in by geothermal gradients. The permafrost geothermal gradient ranges from 11 degrees C/100 in to 8.0 degrees C/100 in with an average of 2 9 degrees C/100 m, and the geothermal gradient of the soil beneath permafrost is about 2.8-8.5 degrees C/100 m with an average of 6.0 degrees C/100 m in the Qinghai-Tibet Plateau. For a minimum of permafrost geothermal gradients of 1.1 degrees C/100 m, the areas of the potential occurrence of methane hydrate (sl) is approximately estimated to be about 27.5% of the total area of permafrost regions in the Qinghai-Tibet Plateau. For an average of permafrost geothermal gradients of 2.9 degrees C/100 m, the areas of the potential occurrence of methane hydrate (sl) is approximately estimated about 14% of the total area of permafrost regions in the Qinghai-Tibet Plateau For the sll hydrate, the areas of the potential occurrence of sll hydrate are more than that of sl methane hydrate. (C) 2009 Elsevier Ltd. All rights reserved