Characteristics and formation mechanisms of the unconformity-related paleokarst reservoirs in the Upper Sinian, Northwestern Tarim Basin, China

In the Late Sinian, the Tarim Basin experienced regional tectonic uplift and subaerial exposure. A regional unconformity was extensively distributed during the succession from the Sinian to Cambrian. As a result, a large number of secondary pores were developed in the Upper Sinian Qegebulake Formation. An integrated study based on petrographical and petrophysical analysis, geochemistry, karstology and fluid inclusions was performed to provide insight into the characteristics and formation mechanism of the Upper Sinian carbonate reservoirs. The reservoir rocks mainly include microbial dolomite, crystalline dolomite and breccias. Reservoir matrix porosity and permeability range from 0.30% to 11.06% and from 0.00156 mD to 1.49 mD respectively.