Research On Deposition Response To Fault In The Su-Wan Segment Of Tan-Lu Fault Zone And The Petroleum Geology Conditions Of The Hefei Basin

Tan-lu fault, a large structural belt and important geological boundary in marginal-pacific area of east China, is a complex geology body, which has strike-slip, extension and compression behaviors on its different sectors during different geological stages. Based on large quantity of practical data and predecessors'research achievements, the following aspects are emphatically studied: the structure characteristics and evolution history of tan-lu fault, the macroscopic relationship between the Su-wan Segment of tan-lu fault zone and Hefei basin, the effects on sedimentary evolution of Hefei basin by Su-wan fault activity. And then, on the basis of geological, geophysical and drilling data, the stratigraphic deposition, tectonic evolution, petroleum geology characteristics in Hefei basin are studied synthetically by using theories of petroleum geology, geophysics and geochemistry, resulting in recognition of potential hydrocarbon accumulation zones and exploration targets. Furthermore, the concepts, fundamental characteristics, identification means and evolution models of strike-slip structure and strike-slip basin are discussed at the first part of this paper.And, the following aspects are emphatically discussed: the geophysics field, dynamics background and the tectonic evolution history of the Tan-lu fault zone. Based on synthesizing the recent data of structural geology and isotopic dating from the fault zone, four evolutional stages of the Tan-Lu fault zone could be summarized, i.e. the left-lateral strike-slip movement in late Triassic, the intracontinental left-lateral strike-slip from later Jurassic to early Cretaceous, the extension and right-lateral strike-slip from late Cretaceous to Eogene and thrusting during Neogene.Hefei basin, closely near to the west of Tan-lu fault, is a Mes-Cenozoic compound superposition basin. Its generation and evolution have a close relationship with the activities of Tan-lu fault zone. By using theories of sedimentology, depositional characteristics of the Hefei basin indicated a good coupling with evolution of the Tan Lu fault zone. In addition, the activities of Tan-lu fault (two times of left-lateral strike-slip in Mesozoic, extension from later Jurassic to Eogene and thrusting during Neogene) have an important influence on basin type, tectonic framework, sequence-filling succession, and formation of different types of tectonic belts in Hefei basin during Mes-Cenozoic.Hefei basin is one of the large continental sedimentary basins with no oil-gas discovered yet at present in East China. Its exploration degree is low, and the existence of hydrocarbon source rock is the key point. In view of higher thermal evolution and lower residual organic matter abundance in Pre-Mesozoic and Mesozoic strata in Hefei basin, three favorable hydrocarbon source rocks are initially confirmed—Dingyuan formation of lower Tertiary, Zhuxiang formation of lower Cambrian, Fanghushan formation of lower Jurassic—based on sample testes and contrast analysis. Finally, according to the division principles and analysis methods of oil-gas bearing system in the superposition basins, nine oil-gas bearing systems are ascertained in Hefei basin, three of which are predominant: C-P—K(E, J2-3) potential oil-gas bearing system, K1—K1, K2 potential oil-gas bearing system and E—E potential oil-gas bearing system. By zone evaluation, four main favorable zones are recognized, which are Shucheng depression, Dingji-Feidong depression, Liu'an uplift, Daqiao depression. Furthermore, based on the traps distinguishing and statistics in the whole area, the traps are sorted and selected using Trap Evaluation System.