Online Journal for E&P Geoscientists

Al Rashid, Samir H.^*1
(1) Saudi Aramco, Dhahran, Saudi Arabia.

The Hanifa Formation in the eastern part of Saudi Arabia consists of a succession of carbonates deposited on the west flank of the Neo-Tethys Ocean. It consists of a lower Hawtah Member, of Early to Mid-Oxfordian age, and the upper Ulayyah Member of Late Oxfordian age. Both members represent third order sequences with each terminating in a shallowing upward, grainstone dominated lithofacies of reservoir significance. Semiquantitative micropalaeontological analysis of cored sections from eastern Saudi Arabian subsurface has revealed varying proportions of benthic foraminifera, bivalves, echinoids, calcareous algae, sponge spicules and stromatoporoid fragments.

 

The biocomponents are organized into stacked successions of palaeoenvironmentally significant biofacies that can be related to high frequency depositional sequences. A foraminiferal biofacies repreents a shallow lagoon, a foraminiferal-Clypeina biofacies represents a deep, low energy lagoon and a sponge spicules biofacies represents an intrashelf basin setting. The most restricted intrashelf basin is represented by abiotic, laminated mudstones and associated submarine evaporates.

Successive palaeoenvironmentally-controlled biofacies represent retrograding and prograding trends related to sequence-linked marine transgressive and regressive events across a southerly deepening basin margin that spans shallow lagoon to intrashelf basin environments. The study has provided a high-resolution sequence framework for the Hanifa to provide intra-reservoir correlative events of flow-layer significance.