Character Of Tertiary Salt-related Structure And Reservoir Forming In Kuche Depression, Tarim Basin

Two sets of gypsolytes are developed in Kuche depression, and therefore avariety of salt structure and salt-related structure are resulted from. Most of saltstructures occur in Kelasu –Tubei, Qiulitage structural belts. In the map view,structures take curved configuration in the west and converge toward to east.Individual salt-bodies with oblong (ellipse, curve) configuration are parallel with thetrend of the structural belt. The configuration and distribution of the salt-bodies arecontrolled by the character of original plastic layers and their covers, structuralsetting and structural movements.Analysis of structural evolution and plastic deform mechanism shows that theevolution of salt structures in Kuche depression underwent two stages, and therapidly deformed phase started in the end of Tertiary to Quaternary. The majorstructural movement did not take place before the Kuche formation deposited, andthe deformation of salt layer was controlled by differential loading, buoyancy andthe structural setting in the period of shallow buried, and the major factor for saltlayer deformation and salt structure formation was the intense structural compressionacted during late Yanshan movement.The attitude structural pattern of salt layer in Kuche depression can be dividedinto five types containing eight styles based on the seismic reflective character of saltlayers. Despite of the intense deformation of salt layer and variety of structure typesin the depression, there is a close relationship between the location of structuredeveloped and the development degree of salt layer, and the intensity of structuralcompression due to the salt bodies moved from subsidence centre to the depressionmargin, and the distribution of the salt structures follows a certain pattern.The structural styles both above and under salt layer are established based on themodern folding and thrusting theory and the analysis of plastic deformationmechanism of salt layer. The structural styles above salt layer include faultpropagation fold, fault bend fold, structural triangular zone, face to face vergencingstructure, tension faulted block and faulted anticline;the sub-salt structural stylesinclude fault propagation fold, fault bend fold, pop-up structure, imbricate structure,structural triangular zone, faulted block and faulted anticline, faulted nose. Most ofthe reservoirs discovered in Kuche depression have close relationship with saltrelated structures. The reservoirs in the depression can be divided into eight types.Among them, the types of salt-core and salt-sheet, salt-anticline, salt-saddle,salt-wall and salt-stock are the best favorable to reservoir forming.Sub-salt structuresof Quele and Wushen are considered as the prospects of black oil accumulation, andSub-salt structure of Qiulitage and the deep structure in Kelasu structural belt areconsidered as prospects for larger gas accumulations, and all of them are the maintargets of recent exploration.