Athens Group’s Daniel Marquez discusses why new 20K control systems require a new approach to specification, acquisition, operation and maintenance procedures.
Acquisition, operations, and maintenance procedures used on current generation BOPs may not be appropriate for 20K BOPs. Photo by Daniel Marquez onboard a drillship operating in Angola.
As the industry moves closer to the deployment date for the first blowout preventers (BOPs) rated to withstand pressures of 20,000psi (20K), there is a notion that these new BOPs are “the same thing, just bigger.” While technically correct, this vastly underestimates the true impact of this new technology on the entire drilling system. Ensuring successful drilling campaigns with 20K well control systems requires a new approach to specification, acquisition, operation and maintenance procedures.
A higher pressure rating requires thicker bodies and bigger rams, which lead to an increase in weight. OEMs may need to implement changes to material characteristics and design parameters to mitigate the weight increase, but the increase in size also impacts the BOP control system in terms of control fluid pressure, flow rate, and volumetric capacity. Additional sensors and software will be required to monitor and control the more complex system.
The design impact extends to other equipment on the rig that interfaces with the BOP, including the riser system, choke manifold, tensioners, riser handling, BOP handling, pressure testing equipment, and contingency systems such as capping stacks. The 20K BOP is now an integrated system of equipment, controls and supporting infrastructure. Ensuring this new system meets the safety and performance requirements of the drilling campaign requires a new approach to the processes that define the way equipment is operated and maintained, as well as the competencies and skills of individuals in charge of the equipment.
The BOP is essentially a “last layer of protection” safety system. Safety is a function of quality, and systems quality is provided through effective systems engineering. Therefore, the new paradigm must be rooted in well-established systems engineering principles. This means the industry must recast the traditional BOP lifecycle from an equipment acquisition focus to an integrated systems engineering focus.
Reliability, availability, and maintainability in the 20K BOP lifecycle are all contributors to safety.
Systems engineering is a comprehensive “people, plant and process” approach that aims to maximize the three fundamental quality attributes of reliability, availability, and maintainability (RAM) from a system rather than component level. Based on the American Petroleum Institute Standard 689 (International Standards Organization document 14224:2006) Collection and Exchange of Reliability and Maintenance Data for Equipment:
Reliability, sometimes referred to as “dependability,” measures the ability of a system to perform its intended function, within stated conditions, for a specified period of time. This is often seen stated as a probability, “the system is 99.9% reliable” or as mean time between failure (MTBF).
Availability, sometimes referred to as “uptime,” measures the ability of a system to be in a condition to perform its intended function at the instant in time when it is required. This is often seen stated as a percent uptime (inverse of non-productive time, or NPT).
Maintainability, sometimes referred to as “serviceability,” measures the ability of a system to be retained in, or restored to, a condition where it can perform its intended function. This is often seen stated as a mean time to repair (MTTR).
20K BOP lifecycle.
While the lifecycle of a 20K BOP may appear similar to existing BOP designs, there is one critical difference: there is no operational history from which to derive lessons learned and best practices. Reactive compliance based on proven-in-use experience is no longer sufficient to ensure operations meet performance and safety requirements. Therefore, it is imperative that the industry proactively establishes a systems-based framework that can articulate the impact of new technology, evaluate the inherent risks, and develop effective design, test, maintenance, and operation protocols.
There are several points on a systems engineering based lifecycle where we can positively impact the RAM of the 20K BOP system. To illustrate this, consider an example scenario.
During a systems engineering based factory acceptance test (FAT), the behavior of the ram locking mechanism is not consistent as the supply pressure is increased. At certain pressures, the ram fails to lock. A review of the design indicates that the problem is not unique to the unit under test, and that the problem could potentially exist in units already deployed to the field.
This scenario demonstrates how a systems engineering based approach can have a significant positive impact on system RAM. The fact that this particular defect was missed in prior development testing and FATs is a result of test plans that do not take a systems approach. In the example above, a requirement for the system to lock at all valid pressures was not adequately validated in the design, nor was it fully tested before the release of the mechanism to the field. A FAT which is based on systems engineering principles establishes direct traceable ties from requirement to test and ensures every requirement is validated in design and verified in test.
The example highlights another key element of the systems engineering approach, which is early and effective stakeholder involvement. A systems-based series of failure modes analysis, requirements verification and design validation milestones involving all stakeholders would have identified and eliminated the ambiguous locking pressure requirement well before delivery. Early stakeholder involvement in systems-based verification and validation milestones is the single most effective way to ensure RAM requirements will be met.
Once testing is complete and the equipment leaves the manufacturing facility, the ability to modify the system is limited. The FAT is essentially the last opportunity to identify issues in the design and increase the system reliability prior to delivery. Afterwards, the lifecycle switches focus from reliability to maintainability. The various levels of testing during the Integration stage of the lifecycle (i.e., pre-commissioning, commissioning, system integrated test, and acceptance) determine the inherited quality level of the design. It is also during this stage that preventive maintenance inspection test programs (PMITP), critical spare inventory management (CSIM), management of change (MOC), training and competency requirements, and other rig-specific processes are defined.
The collective operational framework for the rig is what defines the maintainability of the system. Competent resources, sufficient spares for the entire well control system and the necessary support infrastructure to move, position and access the BOP stack lead to minimum MTTR and high maintainability. Operational frameworks that do not consider the entire system including the maintainability of the extensive support infrastructure can render an otherwise functional BOP inoperable for long periods of time.
It should be no surprise now that we can have a positive impact on the availability of the system during the operation stage of the lifecycle. By this point we should already know the inherited reliability of the system and the specific processes we need to follow to ensure the system is available. It is during this stage that we also need to measure the system uptime and how long it takes to repair it when it fails. However, even if we track these metrics, implement the most comprehensive PMITP programs and contingency protocols, and keep our spare parts inventory stocked, we are limited to impacting only the availability and maintainability of the system; the reliability has not changed because the design has not changed.
The aforementioned lack of operational history makes communicating new lessons learned and operational metrics to the OEM critical for the continuous improvement of 20K BOP well control systems. It is the operational feedback that drives improvements in reliability of future designs. Stronger relationships with the OEM, especially during the operational phase, will be essential for the identification of recurring issues, development of engineering bulletins and product notifications, and help with troubleshooting and remediation strategies.
In summary, a more rigorous systems engineering approach to the specification, acquisition, operation and maintenance of 20K BOP well control systems can ensure safe and successful drilling campaigns despite the current lack of operational history from which to derive lessons learned and best practices. This new approach requires a higher level of cooperation and communication between the OEM and the end user throughout the entire system lifecycle to ensure end user requirements for system safety, quality and performance are verified through appropriate testing, and maintained through improved systems operational frameworks. A systems engineering approach to the specification, acquisition, operation and maintenance of 20K BOP well control systems can positively impact the safety and integrity of any drilling campaign.
Daniel Marquez is a staff consultant at Athens Group with over nine years’ experience, specializing in well control equipment design, risk assessment, verification, operation and maintenance. Marquez also develops tools and provides guidance on regulatory requirements, industry standards, rig quality management, and best practices. He holds a BS in engineering from Texas A&M University.