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为了研究天然气水合物发现区沉积物的CH4生成量,对ODP204航次4个站位(1244,1245,1250和1251)58个沉积物样品进行了5个温度点(25,35,45,55和65℃)的生气量模拟.1244站位的模拟结果显示,气体产物主要为CH4和CO2,未检测到C2+以上的重烃;CH4生成量与模拟温度之间具有很好的相关性,通常在模拟温度35℃时,样品的CH4生成量最大;样品在低温阶段(25和35℃),每克沉积物或有机碳的CH4生成量通常达到最大值.其他3个站位沉积物生气量与1244站位相似.根据4个站位的模拟结果,结合该区的地温梯度,推测海底之下1200m以内的沉积物仍在不断生成生物气,是目前生物成因的天然气水合物的重要气源地;而埋深超过1200m以上的沉积地层已经经过了生物作用大量产气阶段,目前所能产生的生物气的产量已微乎其微,但之前产生的大量生物气对该区水合物成藏贡献很大.而且1200m以上埋深的沉积物开始进入热成因气产气阶段,热解成因气的产生继续为该区水合物提供甲烷来源.
In order to study the CH4 formation in the sediments of gas hydrate discovery zone, five sedimentary samples at four stations (1244, 1245, 1250 and 1251) of ODP 204 were subjected to five temperature points (25, 35, 45, 55 and 65 ℃). The simulation results at Station 1244 show that the major gas products are CH4 and CO2, and no heavy hydrocarbons above C2 + are detected. There is a good correlation between CH4 production and simulated temperature, The CH4 production was the largest at 35 ℃, and the CH4 production per gram of sediment or organic carbon reached the maximum at low temperature (25 and 35 ℃) Based on the simulation results of 4 stations and the geothermal gradient in this area, it is speculated that sediments within 1200m below the sea floor are still generating biogas, which is an important gas source of biogenic gas hydrates ; While the sedimentary strata buried more than 1200m have undergone a large amount of biological gas production, the output of biogas currently produced is negligible, but the large amount of biogas previously produced contributed a lot to the hydrate accumulation in this area And more than 1200m depth of sediment began Thermogenic gas into the gas phase, to produce a pyrolysis gas genesis continue to provide sources of methane hydrate zone.