Abstract:

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.

Key words: Qaidam basin, Jurassic, Tertiary, source rock, hydrocarbon generation history