Types of the Cambrian platform margin mound-shoal complexes and their relationship with paleogeomorphology in Gucheng area, Tarim Basin, NW China

Zhang, Junlong; Hu, Mingzeng; Feng, Zihui; Li, Qiang; Xiangxiang, He; Zhang, Bin; Bo, Yan; Wei, Guoqi; Zhu, Guangyou; You, Zhang

doi:10.1016/s1876-3804(21)60008-3

Cited by 12 publications

(1 citation statement)

References 14 publications

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“…The Gucheng area is situated in the mid-south of the North Depression in the Tarim Basin, on the slope of the Tazhong uplift [28]. It is a second-order structural unit located on the southeast margin of the West Tarim platform [29], adjacent to the Manxi low bulge in the north, and to the Tadong uplift to the east [30,31]. The top surface of the Ordovician carbonate rocks in the target area is structurally a large-wide nose-like uplift inclining toward the northwest, cut by NE faults into several fault blocks with grabens alternating with horsts [28] (Figure 1a).…”

Section: Geological Backgroundmentioning

confidence: 99%

High-Frequency Sea-Level Cycle Reconstruction and Vertical Distribution of Carbonate Ramp Shoal Facies Dolomite Reservoir in Gucheng Area, East Tarim Basin

et al. 2022

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During the sedimentary period of the Ordovician Yingshan Formation, the carbonate platform of the Gucheng area in the Tarim basin was characterized by a distally steepened ramp. Relative sea-level changes exerted a strong influence on the shoal facie dolomite reservoirs of the 3rd Member of the Ordovician Yingshan Formation (the Ying 3 member), sedimented in the context of a shallow water environment on the carbonate ramp. However, previous studies that lacked high-frequency sea-level changes in the Gucheng area prevent further dolomite reservoir characterization. The current work carries out systematic sampling based on the continuous core from the upper and middle parts of the Ying 3 member in two newly drilled exploration wells (GC17 and GC601) and a series of geochemistry analyses, such as C-O isotope, Sr isotope, and rare earth elements (REE), which helps to investigate the features of the shoal facies dolomite reservoir development against high-frequency sea-level changes. With the help of Fischer plots of these two wells, high-density δ13C data (sample interval is about 0.272 m) were merged to construct a comprehensive curve, contributing to characterizing the high-frequency sea-level changes of the upper and middle parts of the Ying 3 member in the Gucheng area and validating the relationship between the pore-vug vertical distribution and high-frequency sea-level changes. Results revealed that the porosity of dolomite reservoirs increased when the high-frequency sea-level fell and decreased when it rose. Furthermore, the karst surface can be found at the top of the upward-shallowing cycle during the high-frequency sea-level falling; the pore-vug reservoirs are concentrated below the karst exposure surface, and porous spaces are more developed closer to the top of the cycle. The high frequency sea-level curve built in this study can be used as a standard for further research of regional sea-levels in the Gucheng area, and this understanding is highly practical in the prediction of shoal facies carbonate reservoir in carbonate ramp.

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