祁连山冻土区DK-9孔温度监测及天然气水合物稳定带厚度

摘要

祁连山冻土区木里盆地三露天井田自2008年首次钻采到天然气水合物实物样品以来,实现了中低纬度高山冻土区天然气水合物勘探的重大突破.天然气水合物钻孔DK-9于2013年发现水合物,通过对该孔长期地温实时监测,获得了稳态的地温数据.结果表明,祁连山多年冻土区聚乎更矿区三露天井田冻土层底界为约163 m,冻土层的厚度达约160 m,冻土层内的地温梯度为1.38℃/100 m,冻土层以下的地温梯度达4.85℃/100 m.根据天然气水合物形成的温-压条件分析,聚乎更矿区具备较好的天然气水合物形成条件,天然气水合物稳定带底界深度处于510～617 m之间.%Gas hydrate was discovered in 2008 in the Sanlutian coalfield,Qilian Mountain permafrost,Northwest China.This discovery was first successfully sampled by drilling in mid-low-latitudes mountain permafrost,and was a breakthrough in gas hydrate exploration in onshore regions of China.Temperature monitoring for gas hydrate scientific borehole DK-9,one of boreholes in the Sanlutian coalfield in which gas hydrate was discovered,yielded steady ground temperature data for both in and beneath permafrost layer for one year.The results suggest that the thickness of permafrost in the Sanlutian coalfield is about 160 m and that the geothermal gradient is 1.38 ℃/100 m in the permafrost layer and 4.85 ℃/100 m below the permafrost layer.Analysis of the gas hydrate stability conditions indicate that the permafrost conditions and gas components are favorable for gas hydrate formation,and the maximum depth of the gas hydrate stability zone (GHSZ) in the Sanlutian coalfield is 510-617 m.