漠河盆地多年冻土区天然气水合物地球化学调查及远景评价

漠河盆地是我国冻土发育的主要地区之一，发育良好的天然气水合物成藏系统，具有天然气水合物形成的良好条件。为了圈定天然气水合物远景区，识别油气聚集体，判别天然气水合物成因，在漠河盆地冻土较发育地区开展了1∶5万天然气水合物地球化学资源调查。结果表明：(1)在森林沼泽景观区，顶空气和荧光光谱指标是天然气水合物勘查的主要指标，借鉴青海木里冻土区天然气水合物地球化学勘查成功的经验，结合AMT、地质等资料分析，元宝山凹陷是天然气水合物较为有利的远景区；(2)岩心样品甲烷碳同位素分析显示，烃类气体分异明显，浅层烃类气体基本为生物气，深部烃类气源主要为混合成因气，个别解吸气为微生物气和热解气；(3)试验性应用了分形-GIS技术，可以细致可靠地进行异常区范围划定，消除干扰因素，有效地圈定水合物远景区。

Geochemical Investigation and Prospective Evaluation of Natural Gas Hydrates in the Permafrost of Mohe Basin

The Mohe basin is a major permafrost region in China.Gas hydrate reservoir system is well deve loped in the basin, and the basin shows good accumulation conditions for gas hydrates. The 1∶50k scale regional gas hydrate geochemical survey was conducted in the Mohe basin to delineate prospecting gas hydrate target areas, and to recognize oil and gas traps and identify the hydrocarbon source. Our results show that: (1) In the forest bog region, headspace gas and fluorescence spectra are the main indices of gas hydrate exploration. Considering the AMT and geology materials, and the previous gas hydrate geochemical work in the Muli permafrost of Qinghai, we consider the Yuanbao depression as the gas hydrate target. (2) Methane carbon isotope analysis on core samples shows that the primary hydrocarbon gas is multi genetic, and only a few adsorbed gases are from bacterial and hydrocarbon pyrolysis. (3) Multiple classification GIS technique employed in this study can exclude the interference factors and precisely delineate the boundary of geochemical anomalies, and can thus be applied in the geochemical exploration of gas hydrates.