| The dolomite reservoir of Qixia Formation is one of the important exploration fields in central Sichuan Basin.
Based on the analysis of petrology, imaging logging, geochemistry and U-Pb isotopic age, the characteristics and genesis
of dolomite reservoir of Qixia Formation in central Sichuan Basin have been clarified. It is believed that: (1) Dolomite
reservoir is mainly developed in the highstand system tract of Qixia Formation, with thin single layer thickness and many
layers, and alternately superimposed with limestone, forming multiple cycles as a whole. Horizontally, dolomite is
distributed in a certain area with good continuity. (2) The rock types of dolomite reservoir mainly include very fine-fine
crystalline dolomite and medium-coarse crystalline dolomite; the reservoir space is dominated by intercrystalline
(dissolved) pores and dissolved vugs; the average porosity is 4.07%, and the average permeability is 3.12 × 10-3 μm2
,
showing the characteristics of medium porosity, medium-high permeability, and weak correlation between porosity and
permeability. (3) The formation of dolomite reservoirs is dominated by quasi-contemporaneous dolomitization, and
slightly reformed by hydrothermal fluid at the end of Maokou. The granular shoal in the high part of the micropaleogeomorphology is the material basis for the development of dolomite reservoirs. The high-frequency sequence
interface controls the formation of early pores, and early dolomitization is conducive to the preservation of these pores.
Based on the above knowledge, the reservoir distribution in Hechuan 3D seismic survey in central Sichuan Basin was
predicted, and the prediction results were consistent with the drilled wells. |
