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High-Resolution Sequence Stratigraphy of the Late Permian Khuff-C in Hawiyah, Ghawar Field
(1) Saudi Aramco, Dhahran, Saudi Arabia
Four high-frequency sequences make up the Late Permian Khuff-C in Ghawar, where each is bounded by well-defined sequence boundaries on core and logs. Each sequence is made up of a Transgressive Systems Tract (TST) and a High Stand Systems Tract (HST), separated by a mappable Maximum Flooding Surface (MFS). Systems tracts are made up of mappable, meter-scale shallowing-upward cycles, for a total of 32 cycles within the entire studied interval.
Khuff-C1 (KC1) is made up of 10 mappable cycles, where the TST of each cycle starts with flooding storm beds and restricted dolomudstones that shallow-up to a regional tidal flat cap. The MFS is totally dolomitized distal lime-mudstone, passing into cross-bedded grainstones. The HST is made up of prograding grainstone overlain by restricted lagoon and tidal flat mudstones.
Khuff-C Sequence 2 (KC2) consists of seven cycles and is defined by an initial transgressive set of restricted cycles with storm influenced facies deposited over the thick, extensive tidal-flat sediments of KC1, which extend field-wide across Ghawar. The middle cycles are made up of storm beds and intensely burrowed shallow sub-tidal pellet packstones, deepening to dominantly open marine lime-mudstone (MFS), and shallowing-up to sand-flat low angle cross-bedded to burrowed peloid packstones. The upper cycle is made up of shallow sub-tidal embayment lime-mudstone shallowing-up to breccciated Paleosol, which is the sequence boundary of KC3.
Khuff-C Sequence 3 (KC3) is made up of 10 cycles with four initial transgressive peri-tidal cycles of lagoonal dolomudstone capped by crinkly laminated to mud-cracked dolomudstone tidal flat facies. This is overlain by a back-stepping cycle-set of grainstone with their distal bryzoan lime-mudstone equivalent (MFS). The HST of KC3 is marked by shallow sub-tidal sand flat facies prograding over distal open marine lime-mudstone. KC3 is marked at the top by a paleosol which also extends across Ghawar.
Finally, Khuff-C Sequence 4 (KC4) consists of five mud-dominated cycles. The base of this sequence is bounded by a field-wide exposure surface of KC3. The TST is represented by transgressive peri-tidal to shallow sub-tidal cycles while the prograding grainstones and the anhydrite behind define the HST.