Abstract

In the Kashagan field, a super giant offshore carbonate field, located in the North Caspian Sea, asphaltene risks have been continuously under evaluation. The previous work done by Yonebayashi et al. (2012)1  included asphaltene risk evaluation incorporating geology and geohistory. Work showed good correlation between fluid sampling location and experimental asphaltene onset pressure (AOP) detection at reservoir temperature. However, a boundary condition of asphaltene precipitation/no-precipitation had some range of uncertainty. The previous work focused at the reservoir temperature condition only.

This paper will present more detailed discussion of asphaltene risk by updating new AOP results, and it will capture range of temperature conditions (i.e. from reservoir temperature to surface operating temperature). For integrating these updates into the Risk-Matrix-Chart proposed in the previous work, geological heterogeneity of fluid sampling location will be taken into account. A study of numerical modeling, applying Redich-Kwong-Soave (RKS) cubic equation of state, treated the geological heterogeneity as variation of asphaltene content, and reproduced asphaltene precipitation envelopes (APE) which were well matched to overall trend of experimental AOP detection. To conclude, this work achieved to reduce uncertainty of asphaltene precipitation boundary at reservoir temperature, and showed a consistent shifting of asphaltene precipitation boundary by temperature range.

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