Types, Petrophysical Properties and Pore Evolution of Late Ediacaran Microbial Carbonates, Tarim Basin, NW China

• Published in: Acta geologica Sinica (Beijing) Vol. 96; no. 4; pp. 1362 - 1375
• Main Authors: TANG, Pan, CHEN, Daizhao, QIAN, Yixiong, WANG, Yuanzheng, YANG, Bo
• Format: Journal Article
• Language: English
• Published: Richmond Wiley Subscription Services, Inc 01.08.2022; Key Laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China; Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China; University of Chinese Academy of Sciences,Beijing 100049,China%Wuxi Research Institute of Petroleum Geology,SINOPEC,Wuxi,Jiangsu 214151,China
• Edition: English ed.
• Subjects: Carbonates; Cementation; Diagenesis; Dissolution; Dissolving; Dolomite; Dolomitization; Dolostone; Evolution; Exploration; Geochronology; Geochronometry; Knowledge acquisition; Late Ediacaran; microbial carbonate; Microorganisms; Mudstone; Permeability; Petrography; Petrology; pore evolution; Pores; Porosity; Radiometric dating; reservoir property; Reservoirs; Stromatolites; Tarim Basin; Uplift; China; Tarim Basin; Late Ediacaran; pore evolution; microbial carbonate; reservoir property; Tarim Basin
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/1755-6724.14974

The Upper Ediacaran microbial carbonates of the Tarim Basin are potential reservoir geobodies for future hydrocarbon exploration with rising interest in exploration for deeply‐buried reserves. However, little knowledge has been acquired on the types of microbial carbonates that are present, the properties of the reservoir and the pore evolution, hampering predictions of high‐quality reservoirs in these carbonates. Integrated with petrography and in‐situ U‐Pb dating geochronology analyses, this study aims to clarify the types of microbial carbonates present and to reconstruct the pore evolution processes of the potential reservoir rocks. The Upper Ediacaran microbial carbonates of the Tarim Basin can be divided into four types, based on their features in terms of different scales (macro‐ to micro‐): microbial laminite, stromatolite, spongiomicrobialite and microbial‐peloidal wackestone/mudstone. Petrophysical properties show that all these microbial carbonates have low porosity and very low permeability with poor connectivity. These carbonates were subject to long‐term and complex diagenetic processes, mainly consisting of dissolution, compaction, pervasive dolomitization, cementation and fracturing. The most important reservoir spaces are contributed by vugs and dissolution‐enlarged pores, which are likely to have been associated with the widespread uplift of the Aksu area in the terminal Ediacaran. In contrast, the cementation of the fine‐to‐medium crystalline dolomite greatly reduced the pre‐existing pores. Pore types are closely related to different microbial fabrics, which played an important role in the pore evolution of the microbial carbonates.