--> Fault Controlling of Non-Exposed Karst Reservoir in Halahatang District in North Tarim Basin

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Fault Controlling of Non-Exposed Karst Reservoir in Halahatang District in North Tarim Basin

Abstract

The marine facies fracture-vug reservoirs in Tarim Basin has complicated evolutionary mechanism and heterogeneity. We choose buried hill district where interlayer karst develops in Halahatang district in north Tarim Basin as example, using certain data as core, imaging logging and slice samples to study the characteristic of fractures, and get the conclusion that 3 issues of structural fractures developed in buried hill district, in which the one of middle Caledonian is effective. Combined with 3D seismic data, tectonic background, reservoir prediction and relationship between fractures issue and tectonic movement, it's concluded that the strike slip faults in middle and late Caledonian to early Hercynian contributed most in development of the karst reservoir in buried hill district. The faults in middle Caledonian further developed into main faults which has largest separation. They influenced fracture-vug reservoirs in two ways: accelerating the development of karst reservoir and destructing oil deposit. The late Caledonian to early Hercynian faults controlled karst reservoirs in 3 aspects: they extend to ground surface and thus precipitate vertical karstification; the fractures of multi issues and scales that associated with the faults increased the contacting area of limestone and meteoric fresh water, which will improve the vertical connectivity and quality of fracture-vug reservoirs; oil and gas were blocked because these faults has small separation. In exploration and well planation in marine facies carbonate, typical weathering crust reservoirs and reservoirs controlled by multi-scale faults should be furtherly considered. Karst reservoirs controlled by faults will gradually become an important target in north Tarim Basin.