| Author's Name: HU Huan1,2, ZHENG Jianfeng2,3, LUO Xinsheng4, DUAN Junmao2,3,
LÜ Qiqi1, SHI Lei4, TIAN Haonan4 |
| Taking the Cambrian Xiaoerblak section in the Keping outcrop area as an example, this study aim to clarify the
differences in the characteristics and distribution patterns of dolomite reservoirs of the Upper Cambrian Xiaqiulitage
Formation in the western Tarim Basin. Based on a systematic analysis of rock thin section, carbon and oxygen isotope
compositions, and U-Pb dating, the conclusions are drawn as follows: (1) The Xiaqiulitage Formation, with a total
thickness of 350 m, is divided into six members, and is composed of grain dolomite, thrombolite dolomite, stromatolite
dolomite, and laminated microbialite dolomite. Seven lithofacies association and two third-order sequences are identified
in the Xiaqiulitage Formation, reflecting the overall transition of tidal flat subfacies to inner platform shoal subfacies from
bottom to top. (2) The reservoir spaces are dominated by matrix dissolution pores, vugs (dissolution cavities), and
intergranular fractures within breccias. The columnar stromatolitic dolomite and thrombolitic dolomite exhibit the best
physical properties, followed by grain dolomite, with the overall characteristics of moderate-to-high porosity and
moderate-to-low permeability. A comprehensive evaluation indicates that the reservoir properties are optimal in Member
1, Member 2, and Member 6, while Member 5 ranks slightly lower. (3) The dolomite was formed during the early
diagenetic stage, and reservoir development is primarily controlled by the combined effects of sedimentary microfacies,
unconformity surfaces, and high-frequency sequences. The reservoirs can be classified into two types: unconformity-karst
dolomite reservoirs and inner mound-shoal dolomite reservoirs. This research provides critical support for evaluating
favorable exploration zones in the Cambrian dolomite plays of the western Tabei area, and offers reliable evidence for
hydrocarbon reservoir assessment, particularly in the Xiongying region. |
