Effect of Faulting on Ordovician Carbonate Buried-Hill Reservoir Beds in Hetianhe Gas Field, Tarim Basin

Ordovician carbonate buried-hill reservoir beds in the Hetianhe (sic) gas field, located In the Mazhatage (sic) structural belt on the southern margin of the Bachu (sic) faulted uplift, southwestern Tarim basin, were studied. Based on field survey, core and slice observation, the general characteristics of carbonate buried-hill reservoir beds and specifically Ordovician carbonate buried-hill reservoir beds in the Hetianhe gas field were discussed. The karst zone of the reservoir beds in Hetianhe gas field was divided into superficial karst zone, vertical infiltration karst zone, lower subsurface flow karst zone, and deep sluggish flow zone from top to bottom. The effects of faulting on Ordovician carbonate buried-hill reservoir beds in the Hetianhe gas field were obvious. The faulting intensified the karstification and increased the depth of denudation. Faulting and subsequent fracture growth modified the reservoir beds and Improved the physical property and quality of the reservoir beds. Moreover, faulting enhanced the development of the dissolution holes and fractures and increased the thickness of the effective reservoir beds. Meanwhile, faulting made the high porosity-permeability carbonate belts, which created conditions for the hydrocarbon accumulation, develop near the fault zone.