Geological Architecture And Evolution Of Tazhong Low Uplift

Paleouplift is an important area of oil and gas exploration.As an continual and stable paleouplift,Tazhong lower uplift is an important oil and gas exploration area in the Paleozoic of Tarim Basin,it is also an important field of Marine carbonate oil and gas exploration and development of basin.This paper studies the geological architecture and the formation evolution of Tazhong lower uplift,by using fault-related folding theory,petroleum geological comprehensive research method and balanced cross section restoration technology,combined seismic profiles,well logging,well drilling,and core data,set up integrated formation system in Tazhong lower uplift,identify regional unconformities and growth strata,divide tectonic-stratigraphic sequence,analyze geological architecture and tectonic evolution of Tazhong lower uplift systematically,determine the key structural transformation,reveal the evolution and formation of paleouplift.Combined the structural background of the periphery and the formation process of Tazhong lower uplift,discuss the causes of the formation of Tazhong lower uplift,propose a reasonable mechanical evolution model,and also analyze the transformation of reservoirs and the control of oil and gas accumulation by tectonic movements.This paper mainly obtains the following conclusions:(1)There mainly exist eight unconformities in Tazhong area:between Cambrian and Sinian?between Upper Ordovician and Lower Ordovician?between Silurian and Upper Ordovician?between Upper Devonian and Silurian?between Carboniferous and Upper Devonian?between Permian and Carboniferous?between Cretaceous and Triassic?between Paleogene and Cretaceous,from bottom to top,it can be divided into five structural layers:basal structural layer,Cambrian to Lower Ordovician structural layer,Upper Ordovician to Middle Devonian structural layer,Upper Devonian to Triassic structural layer,Cretaceous to Cenozoic structural layer.(2)The fault activity is concentrated in the middle and late Caledonian to early Hercynian,the fault system is mainly developed in the Early Paleozoic strata,the fault system in the Mesozoic and Cenozoic strata is not developed.In general,the fault system has the development characteristics of "upper and lower layers".The fault system on the map converges to the east and diverges to the west.(3)The Tazhong No.1 structural belt is an anticlinal structural belt formed by thrusting during the forward propagation of basal fault-bend fold in Tazhong lower uplift.Because of multi-phase activities of the basement fault,a number of secondary faults have developed along the Tazhong NO.1 structural belt,and affected the formation of the slopes of the Upper Ordovician.(4)The growth strata developed in the Upper Ordovician and Silurian shows that,the middle and late stage of the Caledonian is the main period of the activity of the Tazhong NO.1 structural belt,and it is also the main period of the formation of Tazhong lower uplift.Compared with the central and western regions,there are extensive tectonic activities in the eastern part of Tazhong low uplift,the overal uplift of the eastern part is large,the strata is denuded seriously,and the unconformities develops.(5)The formation and evolution of Tazhong low uplift is controlled by the basal development of the fault-bend fold.At the end of the early Ordovician to late Ordovician,it was the main period of the formation of Tazhong low uplift.Tazhong area was dominated by structural uplift.After the late Ordovician,Tazhong low uplift entered the structural widening period and no longer uplifted.In the early Hercynian phase,the reactivation of the basement faults basically ceased to be active,and the low relief in the tower was basically determined.