The Structural Style And Structural Evolution Of Eopaleozoic In Tazhong Uplift Zone

The main purpose of this paper is to discuss the characteristics of tectonic framework, fault styles, evolution history, the relationship between tectonics and hydrocarbon and favorable prospects and targets of Tazhong uplift in Tarim Basin.Based on the studies of predecessors, we have divided the filled strata of Tazhong-uplift into 3 first order sequences and 7 second order sequences in Palaeozoic Era mostly according to the unconformities of stratigraphic distribution, the depositional sequences and reflection characteristics in the seismic profile of Tazhong area.Based on the fine interpretation of seismic profile of Tazhong area, mainly using geologic frame abduction , the denudation of the major unconformities ( T74, T70 and T60) was estimated . The trend of denudation was analyzed.The tectonic framework of Tazhong area presented as"west-east differentiation and north-south dissimilitude". Based on the seismic profile, the major pattern of the faults was thrust fault with high angles and involved in base, and the main thrust faults developed back to back companion faults, which formed flower structure. In the layout, the three orientation faults (NW, NE and EW) were developed in the layout. Based on the analysis of the major pattern of the faults in Tazhong, the feature and the patterns of the fault system was revealed. The patterns of flower structure, imbricated thrust ,Y-fault, back to back thrust fault, and ramp were developed in this zone.With the modeling program, the fractures in the Ordovician carbonate rock were simulated. The dip fracture was the main pattern of the fractures developed in the Ordovician carbonate rock in Tazhong. The orientation of the fractures was different from the north to the south. From the north to the south, the orientation of the fractures was continuously clockwise rotated, which proved that the fracture was compresso-shear.The paper also studied the evolution of Tazhong uplift. The Tazhong uplift was an inherited palaeohigh evolved from Sinian Period. In early Caledonian period, the Tazhong area was in tensional environment ,so a series of normal faults were formed; but in middle Caledonian period it was in compressional environment and the normal faults were turned into reversed faults; in later Caledonian period, tectonic movement slowed down and uplift was falled into a pattern.We can pre-determine the beneficial zone on Tazhong after analysis before. The zone evaluation of Tazhong uplift was carried out according to the above analysis. The sandbar and reef was formed on the slope of the faultâ… , which are beneficial to oil accumulation; the early Ordovician strata of the faultâ…¤was favorable reservoir and trap; These two areas are favorable oil accumulation areas.