--> Abstract: Predicting Reservoir Quality in the Ara Stringer Reservoirs, South Oman Salt Basin, by Zuwena Rawahi and Xiomara Marquez; #90077 (2008)
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Previous HitPredictingNext Hit Previous HitReservoirNext Hit Quality in the Ara Stringer Reservoirs, South Oman Salt Basin

Zuwena Rawahi* and Xiomara Marquez
PDO
*[email protected]

Hydrocarbon production from exploratory wells penetrating the Neoproterozoic-Cambrian Ara stringers in the South Oman Salt Basin (SOSB) have had variable results due to a heterogeneous pore system, multiple evaporitic cements and bitumen plugging. Ongoing sedimentary and diagenetic work, integrated with geochemistry and the structural evolution of the SOSB, showed that Previous HitporosityNext Hit enhancement is controlled by multiple dissolution events. The present-day Previous HitporosityNext Hit distribution is predominantly secondary, formed by dissolution in the deep burial environment. Pore-reducing processes started with the formation of Previous HitreservoirNext Hit bitumen, followed by anhydrite and then halite cementation. Two types of immobile non-pyrolisable bitumen can be distinguished petrographically and are thought to have precipitated from migrating or trapped hydrocarbons. The first bitumen phase occurred as thin rims, lining and partially filling secondary inter-crystalline and stylolite-related pores. It was observed in the earliest developed inter-crystalline secondary pores, suggesting migration soon after early burial replacement dolomitisation and a first dissolution event. The second phase of bitumen was observed as droplets in large dissolution vugs and is associated with microfractures, saddle dolomite and late diagenetic calcite. Mobile, pyrolisable bitumen has not been observed in thin section; its presence is indicated by geochemistry data. Other important pore-occluding phases are halite and anhydrite cementation. Preliminary results indicated that although cementation is abundant, its extent at Previous HitreservoirTop scale can be laterally limited, and locally, trends can be mapped. Bitumen plugging is difficult to predict due to its multiple origins, this requires a better understanding of the relative timing of generation, expulsion and charge events.

 

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain