Types and controls on the dolostone reservoirs in the Upper Carboniferous Huanglong Formation, Macaoba-Heiloumen region, Chongqing

The present paper deals, on the basis of cores, thin sections and physical properties, with the types and controls of sedimentary facies and diagenesis on the dolostone reservoirs from the Huanglong Formation in the Macaoba-Heiloumen region, eastern Sichuan Basin. The dolostone types are composed of grainy dolostone, micritic dolostone, silty to fine-grained dolostone. The reservoir spaces consist of dominant secondary intergranular and intragranular solution openings and associated superlarge solution openings. The dolostone reservoirs from the Huanglong Formation generally belong to the low-porosity and low-permeability reservoirs with micropores and moderate-fine pore throats. The diagenesis favourable for the development of the dolostone reservoirs includes dolomitization, recrystallization, cataclasis and palaeokarstification, of which the dolomitization is wide-spread and most important diagenesis. The shoals and tidal channels are interpreted as the favourable sedimentary environments for the development of the dolostone reservoirs in the study area.