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Technical Paper: Beating the Marginal Well Performance in a Mature Field: San Francisco Field in Colombia

Society: SPE
Paper Number: 94987
Presentation Date: 2005
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Abstract

Mature fields represent a special challenge in terms of drilling, because the net present value of the wells compared to the well investment diminishes with the degree of maturity.  As the value diminishes, less and less time can be invested in reservoir studies to support field activities.  Special workflows are therefore required to allow for a screening of potential infill locations as well as a value assessment.

This paper presents the methodology and processes developed to define the infill drilling locations in the San Francisco field, as well as the execution and the results of the wells drilled, completed, and produced.  These processes were developed after an unsuccessful drilling campaign in 2001 to 2002 and have helped arrest the field production decline.

The San Francisco field is an example of a mature field producing under a mature waterflooding project, at water cut greater than 90% owing to the level of depletion, an unfavorable mobility ratio, and high reservoir heterogeneity caused by the estuarine depositional environment.

A multidisciplinary team was set up to end with recommendations to ensure the coherence of the San Francisco Field development plan and the establish the 2003 and 2004 Drilling Campaigns.  The workflow to identify drilling opportunities includes an analytical approach and a numerical simulation approach.

The analytical approach consisted of accounting for the well declines and the oil in place by sand and by area.  This allowed a definition of reserves block by block and assessment of the possibility of production acceleration through drilling.  A significant effort had to be given to the production allocation to support this workflow. 

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