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ORIGINAL RESEARCH article

Front. Earth Sci.
Sec. Sedimentology, Stratigraphy and Diagenesis
Volume 12 - 2024 | doi: 10.3389/feart.2024.1407400

Lithofacies and diagenetic controls on thrombolitic dolomite reservoir development from the Precambrian Dengying Formation in the central Sichuan Basin, SW China

Provisionally accepted
Yong Li Yong Li 1Benjian Zhang Benjian Zhang 1Gang Zhou Gang Zhou 1Ruifeng Tang Ruifeng Tang 1Hongyu Long Hongyu Long 1Chenglong Li Chenglong Li 1Xi Chen Xi Chen 1Di Chen Di Chen 1Xiaohong Liu Xiaohong Liu 2*Chao Zhang Chao Zhang 2
  • 1 PetroChina Southwest Oil and Gasfield Company, Chengdu, Sichuan Province, China
  • 2 School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan Province, China

The final, formatted version of the article will be published soon.

    Microbialite reservoirs are of great importance in oil and gas exploration. However, there is still a lack of comprehensive studies on the formation mechanisms of thrombolitic reservoirs, a specific type of microbialite. This research focuses on the oldest thrombolitic dolomite reservoir located within the Precambrian Dengying Formation in the central Sichuan Basin, southwestern China. To characterize different thrombolite facies and elucidate the formation mechanism of thrombolitic dolomite reservoirs and their controlling factors, a multi-disciplinary approach was employed, involving core observation, thin section analysis, cathodoluminescence, SEM microscopy, elemental analysis using LA-ICP-MS, and carbon and oxygen stable isotope analysis. Based on variations in texture, four types of thrombolite were identified: 1) distinct clotted thrombolite, 2) diffuse and regular clotted thrombolite, 3) diffuse and irregular clotted thrombolite, and 4) composite clotted thrombolite. Notably, the diffuse clotted thrombolitic dolomite is the prevalent lithology in the reservoir. Through the modification caused by meteoric water, organic acid fluids, and hydrothermal fluids, a reservoir with dominant porosity in the form of primary growth-framework pores, dissolution pores, and vugs was formed. This resulted in the development of two high-quality reservoir intervals within the 2 nd Member and at the top of the 4 th Member of the Dengying Formation. The growth-framework porosity of the thrombolites, epigenetic karstification and tectonic fracturing were mainly conducive to reservoir development. However, various types of cementation have reduced extensively porosity and connectivity within the reservoir. Overall, this study serves as a valuable example of the methodology required to understand meso-and microstructures of deep-buried thrombolitic dolomite reservoirs, including their heterogeneities and diagenesis, as the original structures influence diagenesis.

    Keywords: Thrombolite, Dolomite reservoir, Diagenesis, Precambrian Dengying Formation, Central Sichuan Basin

    Received: 26 Mar 2024; Accepted: 03 Sep 2024.

    Copyright: © 2024 Li, Zhang, Zhou, Tang, Long, Li, Chen, Chen, Liu and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Xiaohong Liu, School of Geoscience and Technology, Southwest Petroleum University, Chengdu, 610500, Sichuan Province, China

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