Well Abandonment—A "Best Practices" Approach Can Reduce Environmental Risk

Abstract Wells are drilled and completed for a typical production life of 15 to 20 years. After a well is depleted, it must be abandoned so that the permeable intervals penetrated by the wellbore are isolated. For an abandonment to be successful, it must stabilize the wellbore and its associated annuli until geologic forces can re-establish the natural barriers that existed before the well was drilled. The isolation of the hydrocarbon-bearing intervals, overpressured intervals, uncemented annuli, and any freshwater intervals penetrated by the wellbore is critical to successful abandonment. The abandonment plan must be based on the types of fluids contained in reservoirs and the well's mechanical condition at the time of abandonment. Government regulations for well abandonment are minimal guidelines for abandonment, and should not be considered finite answers to environmental safety issues. This paper describes "best practices," concepts and techniques that operators should consider during abandonment planning, that will help ensure effective isolation within the wellbore.