Sequence Stratigraphy And Depositional System Of Dongying Formation Of The North Sag Of Liaozhong Depression

The exploration of large and medium-sized structural oil and gas field has entered the middle-late stage of development,and abundant data provides a good foundation for effective prediction of sedimentary system,sand body distribution and searching for new favorable reservoirs.The tortuous exploration experiences in the northern depression of LiaoZhong sag indicates that subtle reservoir exploration under complex fracture structure is difficult or with high risk.Within the period of Paleogene of Dongying formation,LiaoZhong sag has a variety of sedimentary system.Not only provides a good structural trap reservoir,but also combine with good conditions for lithologic,stratigraphic trap oil accumulation.This paper is mainly about sedimentary system in dongying formation of Paleogene system,to study the sedimentary characteristics,discuss the induced mechanism,controlling factors and distribution laws,and to establish a reasonable depositional model for providing effective means guiding further oil and gas exploration.The main achievements and understandings of this paper are as follows;1)setting up the high resolution sequence stratigraphy framework in the study area,which were divided into three third-grade sequences and seven fourth-grade sequences;and pointed out that the third-grade sequence is bounded by unconformity on the edge of the basin and its corresponding integration,and the fourth-grade resolution sequence stratigraphy units are identified by the interface of water subsidence;2)based on the established sequence framework,combine with single well facies classification,seismic facies analysis and connected wells sedimentary comparison,study microfacies characteristic and the distribution characteristics of the sedimentary system,and focus on the development characteristics of distribution rules of sedimentary facies.In the SQd3 period,lakes sedimentary is the main sedimentary in the study area.In the SQd2 period,meandering river delta,braided river delta and sublacustrine fan deposits developed in the study area.In the SQd1 period,lake and meandering river delta sedimentary developed in the study area.3)tectonic movement,the lake level change and provenance system in sequence-sedimentary system all influenced the sedimentary evolution process.Tectonic movement play an important role in controling provenance,palaeogeomorphology and accommodation space;lake level in different fluctuation period formed different types of sedimentary system.Provenance supply decided the types of sedimentary system in the internal space of the lake basin.4)analyze the characteristic of the plane distribution of sedimentary facies in the study area and summarize the evolvement in the study area;large lake sedimentary is the main characteristic of the SQd3 period;sublacustrine fan sedimentary system and large axial delta widely developed in the period of SQd2.5)through the opposite assemblages,trap conditions and the analysis of the conducting system,predict the advantageous area of next exploration in the study area.