Depositional Characteristic Correlation Of Typical Delta In The Third Member Of Shahejie Formation,Dongpu Depression

Due to the unique and complex nature of the geological features,Dongpu Depression formed complex depositional system,which most developed deltaic sediments,including normal delta,fan delta and braided river delta three sedimentary facies.The formation conditions and depositional characteristics of different delta are significantly different,resulting in their different exploration potential.Expand on the depositional characteristics of the third member of Shahejie Formation in Dongpu Depression for the entire deployment and greater breakthrough in the exploration of lithologic reservoirs.Papers based on the overall depositional system to identify and specificly analysis depositional characteristics and controlling factors of the different sedimentary systems,especially to start the detailed study of its sedimentary sequence features,and to set up its vertical sedimentary sequence and sedimentary facies model.The main results achieved with the understanding are as follows:1.Through the the typical wells analysis and summary of the core pillars of the 103 wells in the area,we study the characteristics of different vertical sedimentary sequence of the delta,summarize its facies and facies assemblages,and establish different vertical sedimentary sequences of the delta mode.The normal deltaic sediments exists coarsening-upward and fining upward two vertical sequences,the first of which is more commen of the third menmber of Shahejie Formation,identified a total of 10 kinds of rock facies and eight kinds of rock combined types;the vertical sequence of fan delta was reverse rhythm,identified a total of 13 kinds of rock facies and four kinds of rock combined types representing different microfacies environment;the vertical sequence of braided river delta was reverse rhythm,identified 13 kinds of rock facies and five kinds of rock combined type,having the multi-phase waterways stacked or waterway between the mudstone alternately superimposed on the delta front.2.Based on the mid-hemicycle,select areas with typical depositional characteristics to establish the well profile framework,and contrast sand body with well,analysis sand bodies stacked relationship of delta.Normal delta sand body continuity,extended distance,near the source with fewer sand bodies and flat strata,distant source with more sand body and the obvious foreset,which was imbricate foreset;fan delta sand body is thick and extension proximity of the provenance,with toplap foreset;braided river delta sand body is thin and numberous.3.Through depositional background analysis,summarizes the main controlling factors that form different delta.Provenance,ancient structure,paleoclimate and other factors control deposition,all of these factors play a common role in the formation of a variety of different delta depositional system of Dongpu Depression.Structure and provenance interaction control the type of depositional systems and sedimentary manner;paleoclimate and provenance control the size of the depositional systems and space superimposed manner.Dongpu Depression northern and southern ends gentle slope areas,provenance extends to the direction of NNE and forms the normal delta that along the long axis.On the Western Slope fault terrace belt,provenance extends to the NE and form the braided river delta.In the SWW and southwest part provenance extends to the NE formed the normal Delta.On the east steep is smaller fan delta.Different depositional characteristics,detailed analysis of the formation of different delta depositional setting and depositional characteristics especially sedimentary sequence characteristics and its controlling factors provide the geological basis for the rational development of the oil fields.