Technology Update: Using Schematics for Managing Well Barriers

Abstract

Technology Update Well integrity and well barriers have been part of the exploitation for oil and gas for nearly a century, with the introduction of the blowout preventer (BOP) in the 1920s. The concept of creating well barrier schematics was inaugurated in Norway in 1992, long before the accidents on the Montara platform in 2009 and the Deepwater Horizon rig in 2010 elevated the global focus on well integrity. A Common Understanding Yet there are large variations in the industry’s perception of well integrity and well barriers, despite the daily use of these terms by drilling and well engineers. Well integrity is defined by the Norsok Standard D-010 (Rev. 4, 2013) as an “application of technical, operational, and organizational solutions to reduce risk of uncontrolled release of formation fluids and well fluids throughout the life cycle of a well.” The definition is so broad that engineers might prefer something that lends itself to a more practical, hands-on description. This is where the well barriers principle comes into play. If you ask someone what a well barrier is, you will get many different answers. However, it is possible to unify them on the concept of an envelope. The well barrier envelope is the physical system that prevents fluids from flowing unintentionally from the formation into another formation or to the external environment. The envelope is designed to contain this pressurized effluent. Barrier Envelope Principle The benefit of using the envelope principle is that we can create two independent envelopes, one outside of the other. We will have primary containment of the pressurized fluid, so that no matter where the pressure might escape through the primary barrier, there will always be a secondary containment behind the primary barrier as a backup (Figs. 1a and 1b). To be consistent and to avoid ambiguity, it is best to define the secondary barrier as the last line of defense rather than barrier No. 2.