Sedimentary Reservoir Feature Of Lower-middle Ordovician Carbonate In The Eastern Of Paleouplift Strike Slip Fault Zone In Central Tarim Basin

Tarim Basin is one of the Marine carbonate basins in China.Due to the tectonic evolution of tarim Basin and its surrounding orogenic belts,the Tazhong Paleo-uplift has formed a multi-stage and multi-group fault system,which has a profound influence on carbonate reservoir.This article will strike-slip fault zone in the eastern part of central ancient uplift lower-middle ordovician carbonate strata as the research object,guided by the several basic course,integrated application of earthquake,exploratory well,core,casting thin sections and other data,and the middle and lower ordovician carbonate rocks in the studied area sedimentary petrology characteristics,physical property of reservoir characteristics,reservoir space types,characteristics and so on carries on the system research,and strike-slip fault in the studied area Finally,the response mode of yingshan Formation carbonate reservoir to strike-slip faults is summarized based on the research results of classification,plane deformation,section deformation and subsection deformation of fracture system.In the eastern part of tazhong Paleo-uplift,the tectonic pattern is high in the southeast and low in the northwest.The transformation of paleotectonic stress field in key tectonic periods in Tarim Basin resulted in the formation of faults of different periods and scales,which influenced the distribution and evolution of sedimentary environment.The middle and late Caledonian tectonic evolution is very important to study the stage characteristics of tazhong strike-slip fault,and it is also the key period for the formation of middle and lower Ordovician reservoirs.The middle and lower Ordovician strata in the study area are mainly composed of Yingshan Formation,which can be divided into four lithologic members from top to bottom.The first member and the upper sub-member of the second Member of the Eagle are mainly found in the northern region,and the second member of the Eagle is mainly found in the central and southern regions.The fault system of Tazhong uplift is mainly composed of NW thrust faults and NE strike-slip faults.According to the development scale and extension length of the faults,the strike-slip faults in the study area are divided into three levels.According to the shape,the structural styles of fault plane can be divided into linear,braided and feather structural styles.The structural styles of fracture profile of carbonate strata can be divided into three types: translation strike-slip,negative flower and normal flower.Strike-slip faults are obviously segmented and the deformation characteristics of plane and section are different.Related fracture zones formed by faults can effectively improve reservoir performance and contribute to fluid dissolution and reconstruction of reservoirs.The Yingshan Formation is mainly composed of open platform facies,and several sedimentary cycles are formed by intra-platform shoal subfacies and inter-shoal sea subfacies on the longitudinal plane.The inter-shoal sea subfacies and inter-shoal sea subfacies on the plane are banded and developed in the intra-platform shoal subfacies.There are many types of reservoir rocks in Yingshan Formation,mainly limestone,transitional rocks and dolomite.The reservoir physical properties of Yingshan Formation are mainly characterized by low porosity and low permeability,and the reservoir space types mainly include pores,karst caves and fractures,which can be divided into several subtypes,among which the large cave is the most ideal reservoir space type in the study area.Statistical study shows that the reservoirs in the eastern part of tazhong paleo-uplift are mainly fracture-pore type and void-cavity type.Strike-slip fault plays an important constructive role in carbonate reservoir.The main changes are as follows: the fracture fracture zone generated by strike-slip faults can effectively improve reservoir performance,while the size of fault fracture zone and the configuration of fluid parameters can produce various types of dissolution,which can further improve reservoir space;By superimposing the fracture system and amplitude properties of the top surface of carbonate rocks,it is found that carbonate reservoirs are mostly located near fault zones.In addition,different fracture styles have different influences on karst reservoirs.By comprehensive comparison of the reservoir development characteristics of each section of the three typical faults,it is concluded that the strike-slip superimposed section,pull-apart graben section,braided strike-slip section and oblique strike-slip section are the fracture styles with better reservoir control effect in the area.