Abstract:

The oil-entering periods of the Carboniferous in Central Hubei Depression could mainly be divided into two stages:Indo-China and Yenshan Epoches.The porosity types during the periods consists of exposed corrosion porosity in early stage,shallow-layer corrosion porosity and deep-seated corrosion porosity in the late stage.The reservoir rocks corresponding to the porosity types include:1.powder-fine crystal dolomitite;2.microspar dolomitite(or microsparite);3.dolomitite that is formed of blue-green algae and foraminifer;4.micritic breccia dolomitite;5.micritic limestone.Dolomitites in the lower part of the Carboniferous Huanglong Formation is the main reservoir bed among all in this region since it has more types of reservoir spaces and higher porosity during the periods;the secondary one is the microspar granular limestone in the upper part of the formation.