Operational Risk: Stepping Beyond Bow Ties
This paper presents the multiple-physical-barrier (MPB) approach to operational (or process) risk, an extension of the common bow-tie technique for identifying risk. Bow ties identify a variety of different types of barriers and help communicate safety principles that link causal factors and subsequent actions to a specific event. By narrowing the focus to physical barriers and by developing success paths that enable each barrier to perform its safety function, the MPB approach moves further toward a systematic approach to operational-risk management.
Introduction—Operational Risk, Bow Ties, and Physical Barriers
Operational Risk. One of the more elusive issues in the upstream oil and gas industry is the understanding of process safety or process risk—especially how it overlaps with industrial (or personal) safety—and the types of tools needed to assess and manage it. An important part of this hinges on the role that barriers play in the analysis and what constitutes a barrier. Some companies consider training to be a barrier, others consider certain meetings to be barriers, and still others consider safety procedures themselves to be barriers. Indeed, there is scarce practical agreement between companies as to how process risk is assessed, managed, and communicated. As a result, there can be similarities, but, ultimately, no two process-risk assessments from different companies look the same.
Several different barriers are shown in the bow-tie diagram in Fig. 1. Barrier types there include the well-control program, mud checks, fill-ups, and escalation barriers.
Bow-Tie Analysis. Bow-tie analysis has been widely used in the offshore oil and gas industry as a technique for communicating safety issues and safety control measures. Bow-tie analysis is event based; it seeks to tie causal factors and subsequent actions to a specific event, such as a kick. Bow-tie diagrams help teams better understand the sequences that can lead to serious process or operational risks. They also identify mitigating actions that can be taken to reduce the consequences of a major event.
The MPB Approach—A Pathway to Success
The MPB approach was developed with the help of collaborations from the upstream oil and gas industry. It takes a step beyond bow ties toward a more-direct and -systematic understanding of operational risk so that operators can design their operations to be successful. In so doing, risk is systematically identified and evaluated and can be incorporated into the management system to help ensure the safety of offshore operations.
This paper posits that operational risk stems from the breech, removal, or failure to properly install or maintain a required physical barrier. If all required physical barriers are in place and effective, then there will be no operational safety incidents. If all of the cement-plug barriers, fluid-column barriers, and blowout-preventer barriers had been effective, there would not have been any of the major accident events in the Gulf of Mexico, including explosions, loss-of-well-control events, and major environmental spills. Operational risk is fundamentally about establishing and maintaining MPBs.
Physical barriers are designed, constructed, operated, and maintained to ensure that they can perform under adverse conditions. In many cases, multiple physical barriers are required so that, in case one barrier fails, another is in place to achieve the safety function (e.g., contain hydrocarbons). More broadly, the MPB approach reflects the concept that the number of physical barriers should be commensurate with the risk of the associated activity.
The focus of the MPB approach lies with two leading questions:
- What are the physical barriers required for the operation at hand?
- What is needed to ensure that these barriers succeed in meeting their safety functions?
These questions marry principles from two very different industries (nuclear and maritime). The focus on physical barriers that is foundational to the nuclear safety industry and the ability to diagram and trace how critical systems function (e.g., performance qualification standards) form a key part of training for engineers in the US Navy and the US Coast Guard. Both perspectives were adapted, and templates were developed to diagram this approach as a success path.
It is this understanding of success paths, especially when applied to the physical barriers, that paves the way toward systematically elucidating the risks. It is important to visualize what must be successful in order to understand what can fail. In effect, this approach is designed to increase operational awareness with the aim of managing operational risk more effectively.
This success-path model is straightforward and provides a number of benefits including
- It is a systematic mechanism for getting at the root cause of operational safety risks that can lead to major accidents. The top-down approach starts at the highest levels first and then enables drill-downs to whatever level of detail is needed to identify the safety problem or match the available data.
- It provides a risk-informed communications framework for communicating with rig workers, senior executives, regulators, and everyone in between. Rig workers can identify their roles within the success paths and readily understand how their actions are integral to maintaining the success of the barrier. At the other end of the spectrum, for example, executives are sometimes faced with making decisions regarding new technologies, and key details may not be fully understood. This approach is well-suited to bring them up to speed in many of the technical details.
- A success-path approach enables decision makers to understand the key points required for success and then participate in the discussion about risks and safety. Further, it provides a consistent and rigorous basis for defending the decisions that have been made, whether to senior executives or third parties. The foundations of this approach have been demonstrated to hold up in legal situations.
- It also serves as an important training tool that enables students to grasp the key operational safety issues. Each physical barrier can be systematically analyzed to provide the foundation needed to manage the operational working environment safely.
The value of the MPB approach is that it steps beyond the bow-tie analysis techniques by placing the focus directly where the risk is—namely, on the physical barriers, their safety functions, and the success paths (both automated and human) that are needed to ensure the success and safety of the operation.
The hierarchy of physical barrier, safety function, and success path is not a coincidence. This chain of cause-and-effect logic forms the basis of operational-risk management for a system, a rig, a well, or a facility. Ultimately, however, it is the role of the operational plan or management system to call out strategies for maintaining the success paths.
The MPB approach is sufficiently intuitive for everyday use yet powerful enough for large-scale integration. When it comes to process (or operational) safety on offshore oil and gas facilities, the devil is in the details, but the MPB approach guides its practitioners to find and identify those details systematically. The benefits are not only for the practitioners but also for guiding the entire operational team on a path toward intuitively understanding the safety implications of their roles and implementing a successful operation.
This approach also positions operational-risk management to be quantified at some point in the future. When reliability quantification is incorporated, the safety significance of any component, system, or set of human actions can be compared and evaluated numerically.