Strike-slip fault system and its reservoir-controlling rules in Awati-Manger-transitional area,Tarim basin
A large number of strike-slip faults with small displacement are developed in the transition area between Awati and Mangar depressions in Tarim basin.These faults cut the sedimentary cover of different ages from the basement upwards,and controlled the development of fracture-vuggy hydrocarbon reservoirs in the Paleozoic carbonates,becoming an important target for oil and gas exploration and development in the abdomen of the Tarim basin,and also a hot spot in the study of structural deformation and controlling-reservoir in the Tarim basin in recent years.Based on the results of 3D seismic data interpretation,this paper analyzes the structural characteristics of strike-slip fault system and its internal relationship with the distribution of fracture-cavity reservoirs in the Awati-Mangar transition area.The research shows that:①The strike-slip fault has different scale permeability distribution characteristics in the Ammanian transition zone.From the bottom to the top,it can be divided into three tectonic deformation layers,namely deep tectonic deformation layer(below T(€)2),middle tectonic deformation layer(T(€)3-TO2)and shallow tectonic deformation layer(TO3-TD).On the plane,it can be divided into four deformation zones,namely,southern slope of Tabei(Northern Tarim)Uplift,western slope of Mangar sag,eastern slope of Awati sag and Tazhong uplift.The structural styles of strike-slip faultin sections are different in deformation layers and deformation zones,and the structural combinationsin plane are also different.In general,it constitutes a complex strike-slip fault system.② The strike-slip fault system in the Awati-Mangar transition area is the result of superimposed tectonic deformation of multiple periods,and its formation and evolution process can be broadly divided into three tectonic periods:Middle and Late Cambrian,Middle and Late Ordovician and Siluran-Carboniferous.The activity modes of the same fault are different in different tectonic periods,and the activity modes of different deformation zones in the same period are also different.In general,strike-slip shear displacement predominates.③ The structural geometry and kinematic characteristics(active period and deformation degree)of the strike-slip fault zone significantly control the development of Paleozoic fractuke-cavity reservoirs,and high-quality fractuke-cavity reservoirs are distributed along those parts with large scale,significant strike-slip deformation and high paleostructural location in the Middle and late Ordovician.The location change of the main displacement belt,local oblique tension,displacement reduction or change of a single strike-slip fault are beneficial to the development of fracture-vavity reservoir group,and lithology and local structural combination control the formation of fracture-vavity reservoir.
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