Late leaching under deep burial conditions: a case study from the Miocene Zhujiang Carbonate Reservoir, South China Sea [An article from: Marine and Petroleum Geology]

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Description:
The Zhujiang carbonates are the hydrocarbon reservoir rock of the Liuhua 11-1 field. They comprise three porous zones of around 20 m intercalated with tight zones, parallel to bedding. Thin-section, cathodoluminescence and stable-isotope data were combined with well-log information in order to investigate the origin and spatial distribution of the abundant porosity. The vast majority of pores in the porous zones was generated or overprinted in deep burial settings by late leaching. Two tight zones, however, lack this porosity, because of meteoric cementation and increased compaction and related calcite precipitation prior to late leaching. We propose that migrating corrosive fluids were diverted along bedding-parallel flow barriers of the tight zones and leached the intervals in-between (=the porous zones) thereby emphasizing the depositional pattern.