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Impact of Diagenetic Anhydrite on Reservoir Quality of the Khuff Formation, Greater Burgan Field in Kuwait
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Seventh Arabian Plate Geology Workshop: Pre-Cambrian to Paleozoic Petroleum Systems in the Arabian Plate, Dec 2018, Volume 2018, p.1 - 5
Abstract
The Khuff Formation was deposited in shallow marine to tidal flat environments during Late Permian, directly after the Hercynian Orogeny. The porosity can classified into two categories: 1) Primary intergranular macroporosity of peloidal/ oolitic grainstone. 2) Secondary solution-enlarged porosity and jacked-open stylolite. The primary fabrics are completely dolomitized and replaced by subsequent anhydrite that dramatically reduce depositional porosity. Furthermore, vug- and fracture filling cementation of anhydrite occludes secondary porosity and close remnant pore spaces. There is no evidence of oil bearing from core data and reservoir quality is essentially negligible. Different types of anhydrite can be distinguished under a petrographic microscope including fine-grain “chicken-wire”, porphyrotopic, acicular-felted, lath-shaped, bladed and blocky anhydrite. Petrographic analysis determine that the precipitation of anhydrite coeval early diagenetic conditions related to evaporative concentrated waters in arid-region (e.g. environment enclosed lagoon or supratidal domain). However, Anhydrite also occur as precipitates of hydrothermal fluids after burial, showing association of stylolitic surfaces and pyrite nodules. It expected that the burial diagenesis cause migration and re-precipitation of anhydrite solutions into adjacent and up-dip strata. Therefore, this study suggests that the Khuff Formation away from crest part of Burgan field, where less fluid-rock interactions, provides better potential of hydrocarbon entrapment. This study present an example of destructive impact of burial diagenesis on world-class hydrocarbon province.