Reserch On The Rift Systems And Their Implication To Carbonate Reservoir Development In Tazhong-Shuntuoguole Area,Tarim Basin

Tarim basin is the most important energy exploration target in China,which has tremendous potential oil and gas resource.Several large oil and gas fields have been found there.The Tazhong-Shuntuoguole area is located in the central basin uplift,owning the largest exploration potential.It has experienced multiphase tectonic activity,complicated rift systems and tectoclases.The tectoclases whthin the Ordovician carbonate rocks form a favourable reservoir space.the rift systems of the region therefore have a far-reaching influence on both sedimentary and accumulation.Based on the typical seismic,core and logging data,this paper takes a systematic study on the rift systems,which is important to the further exploration of oil and gas.The rift systems in the Tazhong-Shuntuoguole area are mainly formed by three groups of main faults in north-west,north-east,and nearly east-west directions.The rift systems as a whole shape like a broom opening from east to west.Most of the systems are thrust faults,which are mostly below the Permian strata,broken down to the basement.The faults are divided into four grades,namely 3 first-order faults,29 second-order faults,63 third-order faults and many forth-order faults.According to the genetic mechanism,fault structural styles are divided into thrust nappe structure,stretch structure and strike-slip structure.Tazhong uplift belt rift systems have experienced two tectonic activities and constitute a complex rift system maily with the thrust nappe structures.In the middle Caledonian,fault belts represented by the Tazhong No.1 Fault and Tangbei Fault actived acutely,which formed the north-west and north-east thrust fault belt.From the late Caledonian to the early Hercynian,the faults continue activing strongly,while a new group of north-east trending strike-slip fault belt is formed.Based on the detailed interpretation of 3D seismic data from Katake and Shuntuoguole region in the middle Tarim Basin,Coherent properties are used to detect stratigraphic discontinuities,while seiscrops being extracted for fine structure interpretation.Use the ant tracking technology to deeply represent the information of the peaks and valleys in the target layers.So we can get distribution characteristics of unobvious four-order faults,which is proving that there are strike-slip tectonics in this area.Meanwhile,there are some zones with low coherent properties which are deep grey in the seiscrops along the layer,reflecting the fractured carbonate reservoirs.They can help delineate fracture zones.The distribution and scale of the fault systems play key rloes in the development and distribution of fractures in Tazhong-Shuntuoguole area.The fractures normally develop in the north-west,closing to the trunk faults.There are two formative stages of fratures.Some fine straight horizontal fractures formed in the mid-Caledonian at first,then in the early Hercynian,a group of high-angle fractures were built and cut the first goup of fractures.High-angle fracture wells were located predominantly on the upper wall,closing the fractured surface.The linear density diagram of the fractures reveals that fractures are most intensive near the upper plate thrust faults,as well as the interjunction with main faults andstrike-slip faults.