Well Integrity Management in Brown Fields

Abstract

Abstract Well integrity is a combination of several disciplines integrated into the different phases of the well lifecycle with ultimate objective to prevent well control incidents. The subject of this paper is about effectiveness of various well integrity monitoring techniques at different stages of the field life. It is based on actual Company lessons learned and recent experience in managing well integrity incidents, when all barriers got lost. Wellhead pressure monitoring is one of the most popular methods of well integrity surveillance. It is based on the double barrier envelope concept: primary barrier envelope is the one exposed to pressure; secondary barrier envelope is the one that will be exposed to pressure if primary barrier fails. Therefore, once the primary barrier fails, it is expected to observe pressure at surface as an indication of the failure. Therefore each well operator has internal fit for purpose wellhead pressure monitoring system. Some specific well categories might be monitored more frequently than another due to higher risks associated with these wells. Double barrier policy is a well integrity requirement well-known world-wide. This policy applies to wells with positive pressure at surface capable to flow naturally. This policy is the basement for wellhead pressure monitoring system. However, based on the latest Company’s well integrity experience, this system is applicable for green fields only, with brand new barriers installed and tested. In case of mature brown fields after several decades of production this system may not always work perfectly. It may happen that failure of the primary barrier envelope occurs in the wells with already failed secondary barrier envelope. In this case there is no any "grace" period to respond to the failure and we immediately get a well control incident reflecting in uncontrolled release of well media through failed barriers. Therefore at some point of field development the time comes when secondary barrier envelope is not reliable anymore and additional surveillance activity has to be implemented to ensure safe operating conditions in the fields. This paper warns well operators on the potential gaps in the well integrity monitoring that may lead to the severe incidents. Those gaps may not exist at the early stages of development but appears during the "transition from green to brown" field. The paper helps to recognize the period for activating additional surveillance techniques avoiding unnecessary OPEX impact. It also describes various surveillance techniques for secondary barrier envelope including leak detection, corrosion logging and pressure testing.