Accurate assessment of remaining oil saturation and sweep efficiency greatly depends on the implemented monitoring program, which requires the integration of all available geoscience and engineering data, by effective analysis using statistical and reservoir simulation methods. This will allow improvedunderstanding of sweep, validation of recovery factor and identifying new development opportunities.

Comprehensive reservoir surveillance is also a critical factor for effective reservoir management in achieving optimal hydrocarbon recovery. Monitoring programs encompass the deployment of up-to-date reservoir saturation tools and techniques capable of delivering high-quality data. There are many complications to be considered such as mixed salinity environments, reservoir heterogeneities, tools with limited depth of investigation and mud invasion effects. These challenges must be considered for a successful reservoir saturation monitoring program. Therefore, the value established by an integrated program involves the use of the most efficient approach in analyzing the acquired saturation data and overcoming the field challenges.

This paper presents a comprehensive approach that was implemented on in situ data acquired from a carbonate reservoir that has operated continuously for several decades with pressure support from peripheral water injection. The technique capitalizes on the wealth of data acquired both from saturation and production logs. The prime objectives of this technique are to evaluate remaining oil saturation, remaining unswept oil column and displacement, and vertical/areal sweep efficiency. The strength of this methodology is the capability of efficiently quantifying and mapping remaining oil saturation. This helps in identifying "sweet spots" behind the flood front and thereby guiding future development activities for maximizing hydrocarbon recovery.

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