Decision criteria for updating test intervals for well barriers

Abstract

In this paper, we discuss whether or not the decision-making process regarding test intervals for well barriers should adopt the same decision criteria as those recently suggested for safety instrumented systems (SIS). We conclude that the criterion suggested for halving the test intervals for SIS is also appropriate to use for well barriers. The criterion for doubling the test interval for SIS is, however, not considered appropriate, as it does not give sufficient weight to the uncertainties. A new type of criterion for doubling the test interval for well barriers that better reflects the uncertainties is suggested.

Keywords:

• well barriers
• test interval
• decision criteria
• uncertainty

Acknowledgements

The paper is partly based on work performed in the research centre DrillWell (Drilling and Well Centre for Improved Recovery). The authors acknowledge the Research Council of Norway, ConocoPhillips, Det norske oljeselskap, Statoil, Talisman, TOTAL and Wintershall for the financing. We also acknowledge the financial support from the Norwegian Research Council’s PETROMAKS 2 program. We would like to thank Professor Jan Terje Kvaløy at the University of Stavanger for valuable suggestions. We also acknowledge many useful comments and suggestions from two anonymous reviewers.