Characteristics and genesis of dolomite reservoir of the Lower Permian Qixia Formation in central Sichuan Basin

Marine Origin Petroleum Geology ›› 2021, Vol. 26 ›› Issue (4) : 345-356.

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ISSN 1672-9854
CN 33-1328/P
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Marine Origin Petroleum Geology ›› 2021, Vol. 26 ›› Issue (4) : 345-356.
Sedimentation and Reservoir

Characteristics and genesis of dolomite reservoir of the Lower Permian Qixia Formation in central Sichuan Basin

  • DUAN Junmao,ZHENG Jianfeng,SHEN Anjiang,ZHU Mao,YAO Qianying,HAO Yi
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Abstract

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 micro-paleogeomorphology 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.

Key words

quasi-contemporaneous dolomitization, crystalline dolomite, reservoir characteristics, Qixia Formation, central Sichuan Basin

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Characteristics and genesis of dolomite reservoir of the Lower Permian Qixia Formation in central Sichuan Basin[J]. Marine Origin Petroleum Geology. 2021, 26(4): 345-356
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