This paper addresses limitations of the skin concept as a parameter to diagnose and compare well performance and its impact on current success criteria used in sand control. Based on simple models for radial, hemispherical and linear flow, and supported by field examples from high rate gravel packed North Sea oil wells, this paper concludes that the skin concept is in many cases inappropriate in comparisons of inter-well performance. Since well interventions can introduce pressure drops controlled by intrinsic properties of the intervention, independent of formation permeability, it follows that added skin effects can reflect properties of the formation and not of the intervention alone. It is therefore possible that phenomena observed and documented in the petroleum literature concerning well behavior can reflect problems with the methodology instead of problems with the wells.

Limitations of the productivity index (PI) as a parameter to judge well performance are also addressed. Finally, alternative methods are discussed to analyze gravel pack performance and compare completion success.

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