The Characteristics Of Tectonic Evolution And Its Control To Reservoir In The South Of Laizhouwan Sag

Laizhouwan sag is a Cenozoic marginal sag,which is located in the southeast of Bohai sea,with complex characteristics of oil and gas accumulation.In this paper,the southern slope of Laizhouwan sag is taken as the research object,based on the data of seismic,drilling and logging,the characteristics of fault system are analyzed systematically,and the dynamic evolution characteristics of structure are studied on the basis of various analysis methods and techniques,such as denudation formation restoration,equilibrium section analysis and paleogeomorphology restoration.And the effect of the dynamic evolution on hydrocarbon accumulation is analyzed systematically.Based on the three-dimensional seismic data in the southern part of Laizhouwan sag and geological data such as drilling,core and logging,the basic elements of fault distance,strike and the combination characteristics of the plane and the profile are statistically analyzed,and the types,structural characteristics,activity and trap characteristics of faults are defined.Research shows that there are two types of fault system in the southern slope of Laizhouwan sag,such as strike-slip and extension faults.The strike-slip faults control the formation and evolution of the Laizhouwan sag.The extension faults can be divided into four types:controlled sag fault,early fault,regulation fault and secondary fault.Controlled by strike-slip and extensional fault systems,there are many types of traps in deep and shallow strata.The structural evolution characteristics of the southern part of Laizhouwan sag are analyzed comprehensively by using the techniques of denudation stratum restoration,equilibrium profile analysis and palaeogeomorphological restoration.Different stages of structural evolution and evolution characteristics are divided.The characteristics of fault development,uplift and depression pattern and palaeogeomorphological evolution in different stages and their interrelations are mainly analyzed,which lay the foundation for the study of oil and gas reservoir control.Research shows that the southern slope of Laizhouwan sag experienced four evolutionary stages,which are the early faulted stage of E_1-2k-E₂s₄,the strong faulted stage of E₂s₃,the fault-depression stage of E₂s_1-2-E₃d,and the depression and Neotectonics stage of N-Q.Based on the analysis of seismic,drilling data and structural evolution,the comprehensive control of structural evolution on hydrocarbon generation,reservoir development and reservoir formation is systematically analyzed.The control of structural evolution on the development and migration of hydrocarbon generation centers,sedimentary types,reservoir distribution and hydrocarbon migration in different periods is put forward.Research shows that the oil and gas reservoirs in the southern gentle slope zone of Laizhouwan sag have the characteristics of multi-source hydrocarbon supply,multi-directional transport,multi-circle accumulation,multi-reservoir oil bearing and differential enrichment,and have the distant source"mesh type",double source"ladder type"and near source"lateral type"migration and accumulation patterns.