柴达木盆地第四系陆相生物气形成机理与控制因素

Genetic mechanisms and controlling factors of terrestrial biogenetic gas in the Quaternary of the Qaidam Basin

魏水建 王金鹏 管志强 徐子远 姜桂凤

Wei Shuijian Wang Jingpeng Guan Zhiqiang Xu Ziyuan Jiang Guifeng

柴达木盆地第四系是研究生物气的理想地点。通过对该盆地生物气形成环境及生物气产生过程模拟试验成果进行综合分析,认为陆相生物气的形成主要受温度、菌群类型、地层水性质、沉积速率等条件的控制。甲烷菌的生存温度为0～80℃,最有利的产甲烷菌代谢温度为30～55℃,大致在35℃左右开始出现产气高峰,折算埋深在500m以下。柴达木盆地第四系地层水具有高矿化度和高盐度特征,并且由浅往深逐渐降低,再加上浅层硫酸盐还原带的分布,使得产甲烷菌群的活动在浅表受到抑制,有利于在较深部位生气成藏。快速的沉积作用,使有机质得以迅速埋藏,为后期微生物作用提供了充足的有机质来源。

The Quaternary in the Qaidam Basin is an ideal site to study biogenetic gas.Based on the analysis of the forming environment of biogenetic gas and in combination with the results of modeling experiments of biogenetic gas generation,we have concluded that the generation of terrestrial biogenetic gas is under the control of various factors including temperature,bacterial group types,groundwater properties and sedimentary rates,etc.The survival temperature of bacterium which produces methane is 0-80℃,and the most favorable temperature to produce methane is 30-55℃.The peak of gas generation occurs at 35℃,which corresponds to a burial depth of 500m.The groundwater in the Quaternary of the Qaidam Basin has the characteristics of high salinity.Its salinity decreases with the increasing of depth.In addition,there are sulfate reduction zone in the shallow strata.These factors restrain the activity of methane bacteria in the shallow and surface areas,making it favorable to generate gas in the deeper strata.The rapid sedimentation buries organic matters quickly,which provide abundant organic sources for later microbial activities.

10.11743/ogg20090309