| Zhanhua sag located in the north of Jiyang depression,is an important raw hydrocarbon sag and oil sag in Jiyang depression.However,the exploration in this area is mainly concentrated in the Cenozoic,the structural feature of the Mesozoic Erathem in this area is not understood well currently,which restricts the next exploration activity.In this paper,Guxi area as an example.First,on the basis of the data of geology,geophysical and logging data analysis the lithology in Mesozoic.By sequence boundary 3D seismic interpretation,analysis the horizontal distribution of different tectonic and the structural geometry features in Mesozoic.We think that the Fangzi-Santai groups in Lower-Middle Jurassic is the NW-SE zonal distribution and west thick,east thin,mainly concentrated in the western region;the Mengyin-Xiwa groups in Upper Jurassic-Lower Crataceous is the NW-SE zonal distribution and west thin,east thick,mainly in the eastern region.From the bottom boundary of the Cenozoic,Fangzi-Santai groups appear in the west and Mengyin-Xiwa groups appear in east.In this area develop three faulting systems which are NW,NE and NEE trends.NW trend faults control the sedimentary of the Mesozoic in basin result faulting east and overlap west.The other faulting systems is not obvious for Mesozoic layer which is formed late.Secondly,through the geochemical characteristics of Mesozoic volcanic zone analysis(Major elements,Trace elements and Rare-Earth elements)think the area is influenced the Pacific Plate subduction durning the Mesozoic and near the Andean region.Presumed the Mesozoic volcanic activity is active continental margin and express the intracontinental rift.On the basis of the Mesozoic tectonic development of dynamic background and use the balanced section discusses the tectonic evolution feature.Consider the Mesco-cenozoic in the Palaeozoic cratogene background has expericend the depression stage in Early-Middle Jurassic,rift valley stage in Late Jurassic-Early Crataceous,uplift stage in Late Crataceous and fault depression stage in Cenozoic.Depression stage show the west thick and east thin,rift valley stage show the faulting east and overlap west,fault depression stage show the faulting north and overlap south.According to the superimpose relationship of the Meso-cenozoic basin,the area has been divided four types: depression-uplift-uplift(A),depression-uplift-depression(B),uplift-depression-uplift(C),uplift-depression-depressi on(D).Finally,according to drill core data of the study area,taking the clastic rock reservoirs of Mengyin-Xiwa Formation in Mesozoic,Gubei Sag as example,based on the analysis of lithology,facies,diagenesis,porosity and other fundamental characteristics,this paper explores the influence of tectonic evolution on clastic rock reservoir development from the aspects of compaction,cementation and dissolution.Controlled by tectonic evolution,the development of clastic rock reservoirs is characterized by the comprehensive effects of structure,facies and fluid during the two burial stages,on which the different superposition relations of Middle Cenozoic basin tectonics have different influence.Reservoirs at A zone,near Gubei fault,are mainly characterized by strong degree of compaction,medium degree of cementation,poor development of primary porosity and little development of secondary dissolution porosity.Meanwhile,the reservoirs at B and D areas are characterized by weak degree of compaction and cementation,well development of both primary porosity and secondary dissolution pores.And reservoirs at C zone show weak degree of compaction,strong degree of cementation,undeveloped primary porosity and secondary dissolution pores. |
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