The Time Effect of Hydrocarbon Generation of Source Rocks and the Natural Gas Enrichment in Southern Songliao Basin

The deep depressions in southern Songliao basin underwent multistage tectonic movements,of which the unbalance caused the great differences of source rock evolution in each deep depression,resulting in controlling the deep natural gas enrichment in this region. According to the contribution size of the deep source rock hydrocarbon generation to the hydrocarbon accumulation,the time effect of hydrocarbon generation could be divided into four types such as the continuous subsidence high efficiency type,the Late Mingshui period uplift middle efficiency type,the Late Nengjiang period uplift low efficiency type and the Late Yingcheng period uplift inefficiency type,which can be accordingly classified as the deep fault depression gas enrichment area in its middle part,the surrounding high gas-bearing area,the remained gas area in the east part and the poor gas area in the west part. It is considered that the deep fault depression gas enrichment area in the middle fault depression zone is the most realistic large scale domain for natural gas exploration in Songliao basin.