The Internal Structure Of Strike-slip Fault Zone In Carbonate Rock And Its Reservoir Controlling Function

According to the types of reservoir space,carbonate reservoirs can be divided into pore type,fracture type and vuggy type.For the Ordovician strata in the Tarim Basin,the porosity is generally less than 5%,so it is very important to study how the fault can transform and control the carbonate reservoir.Understanding the alteration of fault zone in carbonate formation is of great guiding significance for hydrocarbon exploration in carbonate reservoir.In order to study the effect of the internal structure of fault zone on the transformation of carbonate reservoir,this paper describes several field strike-slip fault zones in detail from the field of Keping area,Tarim Basin.Firstly,the field strike-slip fault zone is described from macroscopic and microscopic perspectives,including the types of fault rocks developed in the fault zone,the development law of fault cores and damage zone,and the development characteristics of pores in different parts of the fault zone;Secondly,through XRD rock analysis,isotope analysis,rare earth element analysis and other geochemical means to test the samples in the fault zone,analyze the fluid properties in the fault zone,and further study the transformation of the fluid in the fault zone to the carbonate reservoir;Finally,combined with the characteristics of fault zone and fluid properties,a reservoir control model of strike-slip fault zone is established.The results show that :(1)The strike-slip faults in carbonate rocks are dominated by rupture,and the strike-slip faults in low-non-porous rocks have a typical dual structure--fault core and fracture zone.The fault core is mainly filled with fault breccia and calcite: The fracture zone is dominated by cracks and caves.(2)The fault zone underwent an evolutionary process from low maturity to high maturity.The low mature fault zone only has the characteristics of fracture zone,and the fault core is not formed.The fault core of the highly mature fault zone has obvious stratified structure,and the width of the fracture zone is small.Further,establish the evolution model of the strike-slip fault zone of carbonate rock.(3)The dual action of atmospheric fresh water and hydrothermal is the main mechanism of reservoir reconstruction,the fault-dissolution reconstruction is the fundamental reason to control the formation of reservoir,and the cemented fluid of fault core is the vertical migration channel in the fracture zone.(4)The overlapping and intersecting areas of faults are the development areas of high quality carbonate reservoirs,which establishes the reservoir control mode of fault core cementation and fracture zone dissolution and reconstruction in strike-slip faults.This paper focuses on the study of the deformation mechanism,internal structure and reservoir control mechanism of strike-slip faults in carbonate rocks,and clarifies the controlling effect of strike-slip faults on reservoir formation in carbonate rocks,which has important practical significance for improving the success rate of oil and gas exploration in carbonate rocks.