Abstract:

The biogenic gas resource is hugely enriched in the Quaternary of Sanhu （ three lakes） area in Qaidam Basin At present, the proved and controlled natural gas reserves have reached 290503 billion cubic meters In the Late Pleistocene, the lacustrine sediments were mostly distributed in the Sanhu area of Qaidam BasinFrom the foothill to the center of the basin,alluvial fan,fluvial delta and lake were developed.The lake was gradually formed in the Early Pleistocene, and outspread in the Middle Pleistocene finally The lake shrank and formed the salt lake in the Late Pleistocene The appearance of the glacier and the uplift of the QinghaiXizang(Tibet) Plateau in the Early and Middle Pleistocene made the paleoclimate of the Qaidam Basin dry and cold The water temperature of the depositional lake was low and its salinity was highThe unique depositional environments of this area in the Quaternary are the important conditions for forming the large scale biogenic gas poolsThe water environment with a high salinity slowed down the degradation rate of the organic matter The methane bacteria activity was restrained in cold environment for a long time and the generation peak of the biogenic gas was delayed,so the excessive dissipation of the depositional organic matter was avoided during the shallowburial periodMoreover,the massive Quaternary dark mudstone and frequently developed sandstone in Sanhu area provide abundant gas source and constitute a favorable combination of reservoir。

摘要：

柴达木盆地三湖地区第四系蕴藏着巨大的生物气资源，目前已探明加控制天然气储量接近3×1011m3。更新世时期，柴达木盆地的湖相沉积主要分布在三湖(吉乃尔湖、涩聂湖和达布逊湖)地区，自山前至盆地中心依次发育了冲积扇、河流三角洲和湖相沉积，其中湖相沉积分布最为广泛。早更新世湖相沉积开始形成，中更新世湖相沉积扩张并且达到鼎盛，晚更新世湖相沉积开始萎缩并形成盐湖沉积。中、早更新世冰川的出现和青藏高原的崛起使柴达木盆地的古气候变得干旱寒冷，沉积水体温度较低，盐度较高。本区第四纪独特的沉积环境是形成大型生物气藏最重要的地质条件。高盐度的水体环境减缓了有机质的降解速度，长期的低温条件抑制了甲烷菌的活动，避免了沉积有机质在沉积浅埋阶段的过量消耗，推迟了生物产气的高峰期。而三湖地区巨厚的第四系暗色泥岩和频繁发育的砂岩提供了充足的气源条件和构成了良好的生储盖组合。