Independent verification found to improve HP/HT safety

Changes in drilling environments have brought about the need for more robust equipment that can operate safely in demanding conditions.

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Luiz Feijo
ABS

Changes in drilling environments have brought about the need for more robust equipment that can operate safely in demanding conditions. Recent ultra-deepwater drilling has encountered reservoirs that present high-pressure/high-temperature (HP/HT) environments in which temperatures reach as high as 400°F (204°C) and pressure can be as great as 20,000 psi (1,379 bar). These HP/HT reservoirs present significant challenges because the drilling and production equipment that is currently available is designed for lower pressures and temperatures, typically 15,000 psi (1,034 bar) and 200°F (93°C).

While improved capability is necessary to address the challenges, developing effective HP/HT equipment does not necessarily require the development of new technology. It is possible for current technology to evolve to cope with a more exacting operational environment.

HP/HT conditions

The complexity of HP/HT designs is a direct result of the range of factors that impact operations. From a materials perspective, a comprehensive understanding of physical properties and robust analysis of the potential failure mechanisms active in HP/HT and subsea conditions is necessary for satisfactory equipment design validation and verification.

To operate in such a harsh environment, material selection includes evaluation of the temperature, chemistry, manufacturing procedures, the properties of the selected material and anticipated interactions, exposure to the environment (seawater, wellbore, drilling and completion fluids), general and localized corrosion, erosion, elastomers, the design life, in addition to creep that often occurs at high temperatures.

It is evident that there are challenges, but the potential for new designs is tremendous. New tools and equipment could open the opportunity to drill wells that today are not drillable.

For industry to move safely into this technology frontier, it is critical for all of the unproven technologies and applications to undergo a technology qualification process that fully evaluates the design efforts and assumptions.

Validation

To that end, industry is working to determine the best advanced analysis methods from the existing body of knowledge as well as codes and standards. These methods require detailed equipment design verification that can give assurance to regulatory officials and operators that the technology qualification process addresses all of the appropriate failure modes and that hazards associated with HP/HT operations are fully identified and mitigated by appropriate procedures.

The US Bureau of Safety and Environmental Enforcement (BSEE) now requires an independent third-party (I3P) verification process for HP/HT equipment.

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In creating this requirement, BSEE has taken a lifecycle approach to safety that begins with a design review, followed by verification of mechanical integrity. The process includes initial assessment of the design review, prototype testing, and a list of requirements for service that includes documentation required by BSEE.

I3P work has to be done by qualified organizations or individuals with the necessary expertise and independence to provide appropriate guidance. As important as the verification is, the avoidance of any conflict of interest is equally critical for the effective execution of the verification process.

I3P in action

The I3P process involves two phases: verification and validation.

During the verification phase, the I3P conducts an independent assessment of the material selection, design analysis methods, and calculations in accordance with the plans generated by the equipment manufacturers and verifies that all reasonable, potential modes of failure have been identified.

During the validation phase, the I3P verifies that the design validation tests provided are carried out appropriately to evaluate equipment for the identified potential modes of failure. The tests must be witnessed to confirm that they were performed successfully and that they achieved the expected results. The I3P also verifies the equipment fabrication process, inspection, and quality control procedures to be used during manufacturing.

Verification challenges

The mandated verification and validation provides critical guidance from I3P organizations. The industry is learning how to apply the advanced analysis methods used in the process for detailed equipment design verification. It is vital that the design analyses performed are accurate and complete and that they provide a high degree of confidence for each stakeholder.

One of the challenges in HP/HT operations is environmentally assisted cracking and fatigue cracks, which are dominant failures in HP/HT designs. Standards specific to HP/HT drilling equipment designs are still under development. Because of the lack of field data, designs are evaluated from first principles. Functional production, inspection, and quality standards also need to be developed.

Enabling advancements

ABS is working with original equipment manufacturers that are addressing these challenges as they develop new designs for HP/HT applications and is contributing to safety by verifying and validating that the designs follow the guidelines per all applicable API and ASME codes and standards.

One of the objectives is to establish a baseline for ongoing efforts in standardizing the certification process of HP/HT materials and manufacturing processes for global applications. The knowledge gained by the development projects will be instrumental for the classification society certifying materials for HP/HT equipment as certification requirements are developed with the goal of improving safety on deepwater drilling and production units and in preventing environmental incidents.

As a classification society, ABS continues to work with industry to safely move into new frontiers. Ongoing efforts are targeting continuing improvement of I3P services that cover every aspect of the BSEE requirements.

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