Summary
An offshore carbonate oil field in the Arabian Gulf is exhibiting asphaltene
deposition inside the tubing of production wells completed in one of two main
producible limestone reservoirs. This problem significantly reduces well
profitability because of production loss and frequent asphaltene-removal jobs
(solvent soaking). Furthermore, future full-field enhanced-oil-recovery (EOR)
development--namely gas injection--is now planned and might have a risk of
enhancing the asphaltene problem. Therefore, comprehensive study has been
carried out not only to establish less-frequent and more-effective remedy than
the current action but also to evaluate a future risk of gas injection.
The study was initiated with careful review of the fundamental measurements
of asphaltene properties collected during the 20 years of production
history--saturates, aromatics, resins, and asphaltenes (SARA); asphaltene
contents; and asphaltene-onset-pressure (AOP). Subsequently, the mathematical
modeling analysis using those properties was incorporated into the study for
better understanding/predicting of asphaltene-precipitation behavior. This
paper describes the integration/optimization of the
asphaltene-precipitation-envelope (APE) modeling on the basis of all available
laboratory data, and consequently suggests representative APE. The APE-model
validity was evaluated by comparison with actual observation data in the
problematic reservoir.
On the basis of the mathematical models established, several sensitivities
(i.e., mixing with injection gas and blending oils produced from the two main
producible reservoirs) were investigated to assess impacts of the future EOR on
asphaltene risk from the subsurface and surface points of view. Several types
of injection gas were examined, and their risks were compared and identified.
Consequently, the surface-facility design was adequately modified and optimized
in order to minimize asphaltene risk influenced by gas injection.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
25 February 2010
- Meeting paper published:
20 October 2009
- Revised manuscript received:
8 July 2010
- Manuscript approved:
12 October 2010
- Published online:
9 May 2011
- Version of record:
1 June 2011
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