Structural Deformation And Hydrocarbon Accumulation In Shulu Sag

The Shulu sag is located in the southern part of Jizhong depression in Bohai Bay basin.It is a Paleogene "half graben" fault depression controlled by Xinhe fault and distributed in NE direction.From west to East,it can be further divided into western slope belt,middle sub-sag belt,and eastern steep slope belt.As a whole,there is a structural pattern of "three sub-sag,two uplifts and one slope" in the sag.Based on the theory of structural geology,this paper studies the structural deformation of Shulu sag by means of three-dimensional seismic interpretation,structural analysis and balanced section.Combined with hydrocarbon accumulation rocks,reservoirs,caprocks and other accumulation factors,the main controlling factors of reservoir forming are analyzed,and the hydrocarbon accumulation model in Shulu sag is discussed.Get the following understanding:(1)Shulu sag is a horizontal extensional structural family with basement involvement,mainly developed NNE,NE and NWW faults,mainly NE faults;(2)The main structural styles are downwarping fault block,reverse warping fault block,graben Horst type,"Y" type and reverse "Y" type,all controlled by extension stress field;(3)The structural evolution of Shulu sag can be divided into four stages: strong fault depression,slow fault depression,fault activation and depression,which correspond to the sedimentary periods of the third member of Shahejie formation,the second member of Shahejie formation,the first member of Shahejie Dongying formation and the Guantao formation Pingyuan formation respectively;(4)At the end of Guantao formation,the source rocks of the lower third member of Shahejie formation in Shulu sag are mature and generate a large number of hydrocarbon,with a threshold depth of 2800 m.Oil and gas from the lower part of the third member of Shahejie formation are transported to the upper part of the third member of Shahejie formation,the second member of Shahejie formation and the first member of Shahejie formation through faults and unconformities,and are accumulated in the forward structural belt controlled by faults and slopes.