Study On The Mesozoic And Cenozoic Tectonic Evolution In The South Of Kongdian

This article mainly focuses on the structural properties,types,characteristics and combination styles of the Kongnan area located in the southern bulge of Kongdian,as well as the structural evolution and cause of formation.Combining seismic data interpretation results,based on theoretical knowledge of structural geology,dynamics,sequence stratigraphy,seismic sedimentology,etc.,fully combining professional technical software such as Geo Frame workstation,landmark,2dmove,etc.,using balanced section technology to make the research area The tectonic evolution has been restored to explain the structural characteristics of the thrust nappe zone in the study area.Several typical structural regional styles were selected to analyze their structural evolution and genesis,and three typical well positions were selected: Wanggu 1 Well,Guangu 1 Well,and Wushen 1 Well.Geological analysis was carried out to analyze exploratory wells.And its corresponding reservoir porosity,conduct research on the physical properties,lithology,sedimentary facies,and paleogeographic background of the reservoir to determine whether it is a favorable oil and gas accumulation site.In the selected work area study,we divided the fault structure types and styles of the Neo-,Mesozoic,and Paleozoic superimposed basins,and divided a total of four types of structures: compression,extension,twisting,and reversal.,It is judged that the structure of the study area is mainly controlled by three stress systems of compression,extension,and twisting.The Cenozoic basins mainly developed two structural styles: "extension" and "strike-slip".In addition,thirteen basic structural styles are divided,and the typical structural styles of each section of the Mesozoic nappe belt are summarized.It is known that the Lower Paleozoic strata presents high-angle and far-spaced imbricate thrust faults from south to north.The detachment has gone through five stages of development and transformation.In addition,in this study,we also divided the distribution locations of the thrust nappe structural belt,which can be divided into four sections.Based on the analysis,it is concluded that in the first section,the south of Well Wushen 1 includes part of the north side,which mainly develops the decolled-nappe dorsum structure,and the occurrence of the strata is relatively gentle.In the second stage,the thrust was strong,the thrust stacked fold,the reverse thrust fault was developed,and the occurrence of the strata was high and steep,the triangular offset structure was visible,and the Mesozoic strata suffered denudation.The third section is dominated by triangular offset structure,with strong thrust structure and strong denudation at the top of nappe structure.In the fourth stage,the strike of the nappe belt changed,the thrust was weak,and the strata showed low amplitude fold deformation.In this research and analysis of the structural formation period,main structural features and evolution of the study area,we have mainly obtained the following understandings:(1)The Cenozoic strata in the study area show a left-handed shear tension-torsional structural style,which has a certain effect on the compression structure of the Mesozoic strata.(2)The main controlling factors of hydrocarbon accumulation in a typical area are composed of four factors: nappe range,favorable reservoir facies belt,structural fracture,fault drainage and plugging;(3)According to the specific main controlling factors of hydrocarbon accumulation in the thrust nappe zone,combined with other factors,we have divided a total of three typical hydrocarbon accumulation modes.In addition,there are several difficult issues that need to be resolved in this research work:(1)It is necessary to clarify the activity,fault characteristics and evolution of the main fault structures,and clarify the structural characteristics and evolution of the prototype basin;(2)Qualitative prediction and evaluation of fractures in each section of the thrust nappe zone and fractures in favorable zones are required;(3)It is necessary to clarify the control law of structural evolution on favorable reservoir facies,and the control law of structural evolution on hydrocarbon migration and accumulation;(4)It is necessary to give reasonable principles for block evaluation,and give accurate predictions for favorable oil and gas exploration areas and oil and gas exploration potential areas.