Abstract: High-quality hydrothermal karst reservoirs are well developed in the Ordovician dolomite of Maigaiti slope in Tarim Basin.The reservoirs feature in karst fractures and cavities filled with saddle dolomite and hydrothermal minerals such as quartz, pyrite, celestineand siliceous and etc., and their physical properties were greatly improved by inter-crystal pores and dissolved pores formed during hydrothermal karst activities.Analyses of faults in the research area were combined with drilling data to study faulting activities associated with deep hydrothermal fluids and their effect on the transformation of dolomite reservoirs and characterize hydrothermol fluid on profiles.The results show that multi-staged deep and giant fault zones like Qunkuqiake fault zone, Mazatage fault zone and Madong thrust belt in the research area, were perfect places for hydrothermal fluid activities.Areas far from the fault zones and small extentional strike-slip faults may serve as the pathways for the fluids to flow by, and dolomite reservoirs presented themselves as a string of beads on seismic profiles and widely-distributed dots on the plane.Based on the above observation and reservoirsing conditions of the area, we suggest that the dolomite reservoirs in Qunkuqiake fault zone have the potential to be practical exploration targets and widely-distributed dolomite reservoirs controlled by tensional-shear faults in the area shall also be future exploration targets.

Key words: interior dolomite reservoir, Ordovician, hydrothermal fluid, Maigaiti slope, Tarim Basin