东营凹陷古近系储层超压成因及其成藏意义

THE ORIGIN OF RESERVOIR OVERPRESSURE AND ITS IMPLICATION IN HYDROCARBON ACCUMULATION IN THE PALEOGENE OF DONGYING DEPRESSION

利用实测地层压力资料,系统研究了东营凹陷古近系碎屑岩储层超压成因及其与油气成藏的关系,并总结了超压油气藏的分布模式。超压传递(包括超压接触传递和超压连通传递)、欠压实、原油裂解是东营凹陷古近系碎屑岩储层超压的主要成因机制。超压接触传递能够使与烃源岩接触的储层形成强超压高产油气藏,该类油气藏主要分布在北部陡坡带、中央隆起带周缘以及洼陷中央的沙三、沙四段和孔店组;超压连通传递使深层超压流体进入浅层,形成中超压高产油气藏,该类油气藏集中分布在中央隆起带的沙一、沙二段和南部缓坡带的沙三、沙四段;欠压实发生在沙四段、孔店组的膏盐岩层段,不利于油气成藏;原油裂解发生在埋深超过4000m的地层,与油气成藏没有必然的联系。

Based on the measured fluid pressure data,the origin of reservoir overpressure and its relation with hydrocarbon accumulation of the Paleogene of Dongying depression are systematically analyzed and the distribution model of overpressure hydrocarbon reservoirs is summarized.Mechanism for reservoir overpressure includes overpressure transference (divided into overpressure contact transference and overpressure connect transference),uncompaction and oil cracking.The hydrocarbon reservoirs with high yield and overpressure formed due to the function of overpressure contact transference distribute in the third member and the fourth member of the Shahejie Formation and Kongdian Formation in the center of each sag,northern slope zone and the rim of the central uplift belt.The deep hydrocarbon is brought into the shallow strata and forms the shallow hydrocarbon reservoirs with high yield and medium overpressure by the effect of overpressure connecting transference,which distributes in the first member and second member of Shahejie Formation of the central uplift belt and Es3 and Es4 of the southern slope.the function of uncompaction develops in the strata of gypsum and salt rock of Es4 and Ek and is unfavorable to the formation of reservoirs.The process of crude oil cracking usually develops below the depth of 4000m and has not inevitable relation with the reservoir formation.