Deformation Stages Of Strike-Slip Faults In The Tabei-Tazhong Area,Tarim Basin,and Their Petroleum Geological Significance

Tarim basin is a large petroliferous basin in western China with great exploration potential.In recent years,a series of large strike-slip fault zones have been found on the south slope of Tabei Uplift and the north slope of Tazhong Uplift,which controls the distribution and hydrocarbon enrichment of Ordovician carbonate fracture-cave reservoirs,and forms a large oil and gas area of carbonate rocks controlled by ultra-deep strike-slip faults in the Tabei-Tazhong area.However,the active time and difference of strike-slip faults are not clear,which seriously restricts the further research on the formation and evolution of strike-slip faults and their influence on the process of hydrocarbon generation and migration.The development of calcite U-Pb dating technology has injected new vitality into the study of fault activity periods,and has achieved great success in extensional,compressional and strike-slip faults.In this paper,the drilling core samples of calcite cement in typical strike-slip fault zones in TabeiTazhong area are selected,and the U-Pb dating test is carried out.Combined with calcite petrography and seismic data analysis,the activity period and difference of strike-slip fault are clarified,and the coupling relationship between multi-stage activity of strikeslip fault and hydrocarbon accumulation in the Tahe area is preliminarily established.The main understandings obtained in this paper are as follows.(1)The strike-slip faults in the southern slope of Tabei Uplift first developed in the middle Caledonian period and lasted until Himalayan period,showing the characteristics of multi-stage continuous activity;(2)The strike-slip faults in the northern slope Tazhong Uplift were also developed initially in the middle Caledonian period,and lasted only to Hercynian period,characterized by multi-period and short-term activities;(3)The source fault is the foundation,and the matching relationship between fault activity,reservoir formation and oil and gas filling are the key to determine the oil and gas accumulation in the Tahe Oilfield.This study not only has scientific significance to deepen the understanding of multi-stage complex tectonic movement of strike-slip faults in Tabei-Tazhong area,but also helps to improve the efficiency and success rate of oil and gas exploration and development in this area.