--> Abstract: Ara Stringer Carbonate Modelling: A Case History, by Andrew Faulkner, Saima Fatma Sayyed, and Dietmar Mueller; #90077 (2008)

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Ara Stringer Carbonate Modelling: A Case History

Andrew Faulkner*, Saima Fatma Sayyed, and Dietmar Mueller
*[email protected]

The Ediacaran-Early Cambrian Ara Group intra-salt carbonates located in the South Oman Salt Basin are a unique hydrocarbon system, which currently produce oil and gas from the oldest (producing) reservoirs to be found. The depositional model, facies associations and subsequent diagenetic overprint of these reservoir units provide a challenge to reservoir description and static model construction. A field in southern Oman offers an excellent example of how these reservoirs are modelled. The first step is to capture the uncertainties in facies architecture and property distribution. The second step involves integrating these uncertainties iteratively with dynamic data to produce a robust reservoir model. The field was discovered in 1978 and was brought on stream in 1982. With ever increasing gas-to-oil ratio (GOR), additional oil production is constrained by the ability to handle the produced additional gas. A robust depositional model exists for the A4C Ara Group carbonate stringer. The reservoir zonation is based on sequence stratigraphic correlations that form the framework for the reservoir architecture and reservoir zones. Reservoir properties are highly variable. There is evidence for a porosity/depth trend, which may or may not be related to porosity reduction below a hydrocarbon-water contact. There is pervasive salt, anhydrite and bitumen plugging throughout the reservoir, however the effects of these plugging agents are localised. The A4C stringer exhibits an excellent relationship between facies and porosity, with porosity modelling biased towards facies, using facies transition simulation. There is no evidence of compartmentalisation, as confirmed by interference and formation pressure data, which exhibit good connectivity and communication between the wells. Flow units have been identified based on the integration of static and production log data. These have improved the history-match for the field and also our ability to predict production and GOR from the producing wells.


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