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

Abstract

The marine facies fracture-vug reservoirs in the Tarim Basin have complicated evolutionary mechanisms and heterogeneity. We chose buried hill district where interlayered karst develops in the Halahatang district in northern Tarim Basin, using certain data as core, imaging logging and slice samples to study the characteristic of fractures. We conclude that three phases of structural fractures developed in the buried hill district, in which the one from the middle Caledonian is effective. Combined with 3D seismic data, tectonic background, reservoir prediction and relationship between fractures issue and tectonic movement, we conclude that strike slip faulting in the middle and late Caledonian to early Hercynian contributed significantly in the development of the karst reservoir in the buried hill district. The faults in the middle Caledonian further developed into main faults, which have the largest separation. They influenced fracture-vug reservoirs in two ways: accelerating the development of karst reservoir and destructing oil deposits. The late Caledonian to early Hercynian faults controlled karst reservoirs in three ways: 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 fracturevug reservoirs; oil and gas were blocked because these faults has small separation. In exploration and well planation in carbonate marine facies, typical weathering crust reservoirs and reservoirs controlled by multi-scale faults should be considered further. Karst reservoirs controlled by faults will gradually become an important target in north Tarim Basin.