柴达木盆地北缘和西部主力烃源岩的生烃史

柴北缘昆特依凹陷小煤沟组烃源岩具有两次生烃过程,侏罗纪末期部分深洼进入生烃门限,随后由于抬升停止生油,第二次于始新世早期开始大面积生烃,使得冷湖构造经历了两次成藏;赛什腾凹陷烃源岩主要为大煤沟组,只有一次生烃过程;鱼卡凹陷侏罗系烃源岩在渐新世早期才进入生油门限,至今只有一次油气聚集期。受昆仑山活动的影响,柴达木盆地西部第三系烃源岩主力层段在盐湖相和咸水环境中形成,生烃过程只有一次,在上新世早-中期进入生油门限,成熟度普遍较低,只有局部达到生油高峰,不同构造部位进入生油期的时间和深度有一定差异。

Hydrocarbon generation history of major source rocks in the northern edge and western part of Qaidam basin

Source rocks in the Xiaomeigou Formation in Kunteyi sag,northern edge of Qaidam basin,experienced two hydrocarbon generation processes.At the end of Jurassic,some part of the deep sag reached the hydrocarbon generation threshold,but oil generation ceased subsequently due to uplifting.The second widespread hydrocarbon generation began in Eocene.Thus Lenghu structure experienced two stages of hydrocarbon accumulations.The Dameigou Formation,the main source rock in Saishiteng sag,generated hydrocarbons only once.The Jurassic source rocks in Yuka sag entered the oil generation threshold in early Oligocene with only one hydrocarbon accumulation stage.Due to the influences of Kunlun mountain tectonic movement,the major Tertiary source rocks in western Qaidam basin,which were depositedin salt lake and saline water environments,did not entered the oil generation threshold until the early and middle Pliocene,and the maturities were generally low with only some areas could reach peak of oil generation,and the time and depth that the source rocks entered the oil generation threshold varied to some extent in different tectonic positions.