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。