Architectural Research Of Delta-Beach Bar System On Es2 Formation In Shengtuo Oilfield

The continental oilfields in eastern China have gradually entered the middle and late stages of development,facing serious problems of injection-production contradictions and difficulty in tapping potential in the next step.There is an urgent need to systematically characterize the underground reservoir architecture,so as to provide geological information for the prediction of the distribution of remaining oil.In this paper,taking reservoirs of 1^st and 2nd sand formations in the second member of Shahejie Formation in the second area of Shengtuo Oilfield,Dongying Sag,Bohai Bay Basin as an example,using core,dense well logging,seismic and inter-well tracer data,fine isochronous stratigraphic framework of the study area were built.According to the isochronous stratigraphic framework,the types and distribution characteristics of sedimentary microfacies were clarified,and the single sand body architecture model of shallow water delta-to-beach bar system was established.The following main results and understandings have been achieved:（1）The stratum pattern of the 1^st and 2nd sand formations in the second member of the Shahejie Formation is the"accumulation-equal thickness"type,the thickness distribution of zones and sub-zones is stable,and the thickness of sub-zones is generally less than 6 meters.（2）Two types of sedimentary systems,shallow-water delta and beach bar,are developed in the 1^st and 2nd sand formations of the second member of Shahejie Formation.The shallow water delta system develops distributary channel,mouth bar,overbank and inter-channel microfacies,while the beach bar system develops high-energy beach bar,low-energy beach bar and inter-bar shallow lake microfacies.The single channel sand body is strip-shaped,about 150～450 meters wide and 2～4meters thick;the single estuary bar sand body is about 400～550 meters long,300～400meters wide,and about 3～4 meters thick;a single beach bar sand body is lenticular,with large scale differences.Large-scale beach bar sand bodies are generally about600～850 meters long,400～550 meters wide,and 3～5 meters thick;small beach bar sand bodies are generally about 350～550 meters long,200～350 meters wide,and 2～3 meters thick.（3）The single sand body contact relationships of the shallow-water delta-to-beach bar system are diverse.Among them,the single sand body contact styles in the delta plain are separated by mudstone（disconnected）,superimposed（weakly connected）and overlapping（strongly connected）.The contact patterns between single sand bodies in the delta front are mainly mudstone separation type（disconnected）and superimposed type（weakly connected）;the contact relationships between single beach bar sand bodies are mainly mudstone separation type（disconnected）and splicing type（weakly connected）.