祁连山哈拉湖坳陷天然气水合物地球化学勘查

自祁连山冻土区木里坳陷发现天然气水合物以来,南祁连盆地开始成为中纬度冻土区天然气水合物调查的重点地区.2014年在哈拉湖坳陷开展了1:10万地球化学调查,目的是为天然气水合物远景预测提供地球化学依据.调查面积3000km2,采样密度1点/2 km2,分析了天然气水合物和油气化探指标.在哈拉湖坳陷圈出了与三露天水合物矿藏类似的地球化学综合异常,面积大于30 km2,异常组合为酸解烃甲烷、酸解烃干燥系数、丁烷异构比、顶空气甲烷和荧光F320,这些指标存在组分分带现象.进一步研究表明,烃类气体主要来源于深部的凝析油伴生气和煤型气,异常区发育有利于天然气水合物形成的冻土厚度.调查结果表明,地球化学技术适用于中纬度冻土区天然气水合物勘查,能够圈出天然气水合物远景区.

Geochemical exploration of natural gas hydrate in Halahu Depression of Qilian Mountain

South Qilian basin has become the key area of natural gas hydrate survey in the mid-latitude permafrost since natural gas hydrate was discovered in Halahu Depression.The 1:100000 geochemical survey was carried out to provide evidence for prospective prognosis of natural gas hydrate in Halahu Depression in 2014.Natural gas hydrate and oil-gas geochemical indexes were analyzed in 3000 km2 survey area,with the sampling density being 1 sampling site per 2 km2.Geochemical anomalies (>30km2) similar to Sanlutian hydrate despoit were delineated,where the abnormal combination of acidolysis methane,acidolysis aridity coefficient,butane isomerization rate,headspace methane and fluorescence 320 exhibited compositional zoning.Further studies show that condensate and coal-type gas were the main source of hydrocarbon gas,and the development of abnormal area was beneficial to the formation of the depth of natural gas hydrate.The results of the survey show that the geochemical technique is suitable for the exploration of natural gas hydrate in the mid-latitude permafrost,and could delineate the prospective area of natural gas hydrate.