用超压释放法确定烃源岩排烃期次——以古龙凹陷青山口组为例

The Expulsion Hydrocarbon Periods of Source Rock by Release of Overpressure—An example of Qingshankou formation in Gulong sag

为了研究松辽盆地古龙凹陷青山口组超压烃源岩排烃期次,在超压烃源岩排烃机制分析的基础上,利用声波时差建立的超压释放期次的研究方法,得到青山口组超压曾发生过3次释放,它们分别是嫩一段沉积末期,嫩四段沉积中后期和明水组沉积末期,目前正处于第4次演化过程中。经超压释放期与烃源岩生烃门限期的比较,认为古龙凹陷青山口组超压烃源岩的主要排烃期是明水组沉积末期,与大庆油田萨尔图、葡萄花、高台子等油气藏的圈闭形成期是同期的,这是大庆油田形成的重要条件之一。

By means of expulsion hydrocarbon mechanism of overpressure source rock, the method for release periods or times of overpressure is presented by interval transit time, obtaining that the overpressure of Qingshankou formation in Gulong sag in Songliao basin was ever released for three times. They arc the end period of kin, the middle-late period of kin4 and the end period of k2m, and it is now in the fourth evolution process of overpressure. By comparison of these overpressure release periods with periods of oil threshold of k1qn source rock, the end period of k2m sedimentation is considered to be main expulsion hydrocarbon period of overpressure source rock of k1qn. This coincides with the periods of hydrocarbon accumulation in Saertu, Putaohua and Gaotaizi reservoirs in Daqing oilfield, indicating that the oil and gas expulsion from the overpressure source rock of Qingshankou formation were favorable to accumulate in large scale into these reservoirs. It is one of important conditions to form Daqing oilfield.