Characterization and origin of a dolomite reservoir in weathering crust: example from Ordovician in the Tabamiao Region, Northern Ordos, China

• Autores: Xianghao Meng, Youli Wan, Xiaoliang Bai
• Localización: Carbonates and Evaporites, ISSN 0891-2556, Vol. 33, Nº. 2, 2018, págs. 195-210
• Idioma: inglés
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• Resumen

  • A set of typical Ordovician paleo-weathering crusts have developed in the dolomite reservoir of the Ma5 section within the Tabamiao region, Northern Ordos, China. The paleo-weathering crust of the dolomite reservoir is divided into two parts: the Ma 5 5 submember, which contains the dolomite reservoir, and the karst reservoir, which contains all sequences above the Ma 5 5 submember. The main rock types in the Ma5 submember are dolomite with gypsum and muddy to micritic dolomite. The lithologic facies are fracture breccia, crackle breccia, mosaic breccia, chaotic breccia, and matrix-rich mosaic breccia, which reflect the degree of corrosion in the research area. The reservoir lithology is dominantly powder to finely crystalline dolomite. The sedimentary sequence was important in the development of the karst reservoir. The results of the present study suggest that the carbonate reservoir was formed by constructive diagenesis, including dissolution, dolomitization, and fracturing. In addition, intercrystalline pores, dissolution pores, and fractures developed within the weathering crust of the dolomite reservoir. Furthermore, the dolomite contains a significant amount of porosity, which promoted development of the dolomite reservoir and was mainly formed by intercrystalline dissolution.