CORROSION CONTROL — Conlusion: Integrity management must include practiced failure plans

June 8, 2009
Reliance on integrity management policies, processes, and practices can lead to a false feeling of security.

Reliance on integrity management policies, processes, and practices can lead to a false feeling of security. An operator must have a systemic and rehearsed approach to urgent operational failures if it is to ensure a response that limits potential damage to the environment, as well as to its reputation and business.

Intelligent pigging has proven useful in assessing pipeline condition for both multiphase and oil transport lines. It sets a new baseline for future life predictions by corrosion modeling or growth extrapolations. Intelligent pigging, however, can miss defects, resulting in unanticipated pipeline leaks.

The first article of this series (OGJ, June 1, 2009, p. 54) concentrated on microbial-influenced corrosion (MIC) modeling and subsequent intelligent in-line inspection of Forties pipelines. This concluding article details a leak that occurred despite these efforts and the response to it.

Forties leak

An oily sheen on the sea surface on Apr. 4, 2008, disclosed a pipeline leak. Pipeline shut-in occurred immediately and a remotely operated vehicle inspection vessel mobilized to investigate the leak. The leak lay about 258 m downstream of the pipeline tie-in spool piece flanged connection at Forties Bravo. It displaced the sandy seabed near the leak hole, creating a 2-m deep hole.

This leak hole lies at the weld junction of the Forties Bravo to Forties Charlie 20-in. OD pipeline (Fig. 1).
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A diving support vessel and Plidco pipeline repair clamp mobilized to the leak site a few days later. Divers inspected the leak site and confirmed it as being at the intersection of the line pipe spiral weld and the circumferential butt weld between two pipe lengths, near the bottom of the pipe. Fig. 1 shows the leak hole.

Pipeline hydrotesting at 52.5 barg (1.5 x 35 barg) to confirm integrity of the pipeline at a further-reduced maximum allowable operating pressure of 35 barg followed installation of a repair clamp. The pipeline returned to operation for a short period Apr. 13, 2008, before the planned platform maintenance program and tie-in of the replacement pipeline a few days later.

Although the June 2007 in-line inspection identified metal loss at the leak site, the reported 24% of peak depth (3.05 mm of 12.7 mm nominal WT) was not seen as suggesting a risk of failure. Of the 8,181 internal metal loss features reported between 2% and 85% of peak depth, a total of 748 had peak depths of 24% or more. Identified corrosion mechanisms could not account for the loss of the remaining WT from 76% (9.65 mm) to zero between June 2007 and April 2008.

The inspection tool’s stated minimum pitting detection capability was 7 mm diameter, although it might also detect slightly narrower pits. Reduced detection capability occurs at welds, though this is not specifically stated in datasheets. Automatic feature recognition and sizing software size the vast majority of features. The larger features are subject to additional manual sizing, increasing the confidence they were accurately sized.

The metal loss reported at the leak site was not initially subject to manual sizing, but manual sizing following the leak yielded no change in assessed metal loss dimensions at the weld. PII confirmed the absence of discernible, deep metal loss at the leak site during its reexamination of the in-line inspection trace.

The precise nature of the eventually failed defect at the time of the in-line inspection can no longer be determined for the Forties Bravo to Charlie pipeline. But in the absence of another credible cause, the leak was ascribed to an original weld defect combined with progressive deterioration due to internal corrosion, eventually removing remaining WT at the weld. The original weld defect likely consisted of a lack of side-wall fusion not large enough to have been detected by the original weld radiographs or to have failed the pipeline commissioning hydrotest at 193 barg.

At the time of the in-line inspection, the weld defect likely had the form of a near through-wall feature outside the detection capability of the in-line inspection system. A probable loss of containment lay outside the detection capability of the in-line inspection tool.

In-line inspections will generally provide reliable condition information for line pipe, in line with their stated capabilities. But their capabilities may not apply to certain pipeline features, including welds. Though in-line inspection can be part of a pipeline condition monitoring plan, it does not fully confirm integrity of a pipeline. A residual risk remains of failure due to defects, including metal loss features, outside the detection capabilities of the in-line inspection tool.

Rapid response

Complacency or over confidence in modeling, analysis, risk-based inspection, and intelligent pig programs can hinder swift operational response to failures. Fostering an operational ability to launch an intensive engineering effort is paramount to achieving a positive outcome when a pipeline fails. Apache faced two scenarios for response and in both cases showed what can be achieved when decisive leadership focuses on operational problems.

The first scenario was responding to the original findings of the intelligent pig run of June 2007 on the PL55 Forties Bravo to Forties Charlie multiphase pipeline. The quantity, nature, and severity of the defects, the future life-extension requirements of the pipeline, and a risked cost-benefit analysis undertaken by a small team within 3 days of receiving the intelligent pig data guided the decision to replace the pipeline. The replacement project started with no personnel, materials, or contracts in place. It required signing 12 new contracts and agreements, production of 108 specifications and procedures by Apache and its contractors, and 31vessel-days of installation work.

Successful completion of the project took 95 days, starting on receipt of an email from the intelligent pigging company, stating “we have identified some deep features” and ending with the final survey of the trenched, buried, and hydrotested pipeline ready for tie-in. Despite the fast-track nature of the project, pipeline installation took place within 1 day of the original base line schedule produced 6 days into the project.

Beside being executed swiftly, the project complied with the full legal requirements of and support from the Department of Business, Enterprise, and Regulatory Reform and the UK Health and Safety Executive. Execution delivered all normal safety requirements, exceeded required specifications, and occurred on budget and without accidents. This speed of delivery is an achievement when compared with the last pipeline replaced in the Forties field in 1994, which cost more to install and took more than 2 years to complete.

The new Forties Bravo to Forties Charlie multiphase pipeline is designated PL2496.

Installation of this clamp as repair to the weld junction of the Forties Bravo to Forties Charlie pipeline took a total of 6 days following detection of the leak (Fig. 2).
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The second scenario for an operational response came 2 weeks before decommissioning the original Forties Bravo to Forties Charlie pipeline when the platform reported a small slick. Repair entailed the installation of a clamp by divers in 6 days: 1 day for ROV vessel mobilization, 2 days waiting on weather, 1 day of ROV inspection, 1 day for diving-support vessel mobilization, and 1 day to install and test the clamp (Fig. 2).

Timely installation of this clamp prevented any additional environmental damage, allowed production of an additional 34,000 bbl of oil before decommissioning the line and enabled full decommissioning of the pipeline and suitable protection of the line following decommission and before recovery.

The employment of mission analysis and the requirement for a sense of urgency led to the fundamentally successful response operations. Mission analysis or maneuver theory is the military strategic and tactical philosophy of planning; utilizing surprise, speed, and economy of effort. This military battlefield proven method transfers well to the business environment.1 2 Maneuver theory requires aggressive, decisive, timely and well informed decision making supported by:

  • Porous, flexible, and rapid planning.
  • Devolved decision making.
  • Organization capability.
  • Initiative.
  • Trust, training, and competence.

Applying a sense of urgency evolves from recognizing time as a constraint on a project along with cost, quality, risk, and benefits. A sense of urgency, however, does not allow discarding or ignoring the process or discipline of project management. Time as a major constraint actually requires applying more discipline, structure, leadership, and clear risk-based decision making.

Apache’s key focus areas included:

  • Senior management commitment. Full commitment and support by senior management allows the operational staff to move forward with clear objectives and boundaries, enabling speedy decision making.
  • Leadership drive. Applying all the qualities and functions of leadership into the project management process from concept to closeout ensures implementation of command, control, and communication throughout the project.
  • Contractor-management interface. Understanding the contractors’ business at both technical and commercial levels but specifying only functional delivery criteria ensures performance, efficiency, and effective support of contractors in the delivery of their services. All key stakeholders should be involved and informed at project initiation and through its lifecycle to final commissioning and beyond.
  • Small, flat, focused internal teams. Keeping the project team tight reduces interfaces and accelerates communication. It also creates individual responsibility and commitment to delivery of the project, rather than relying on a process or committees to drive outputs.
  • Risk appreciation though knowledge and competence. Employing competent experienced staff and contractors ensures understanding the technical risks brought by the project and inherent risks at the worksite.
  • Configuration management. This process ensures all parties have the latest knowledge and understanding of project design.

Apache previously used this mission-oriented approach in a 2004 Forties repair: replacing the 12-in. OD Forties Echo export riser with a new steel riser in 84 days from a standing start and with an installation contractor other than that which had performed the initial installation.

Riser replacement entailed installing a J-tube on the end of a redundant mud outfall caisson, floating out a steel riser from Leith, UK, pulling and plastically deforming the steel riser up through the new J-tube and existing caisson, installing new spools subsea, and welding the riser into new topside piping.

References

  1. Pech, R.J., and Slade, B.W., “Business Maneuver: Exploiting Speed and Surprise as Key Elements,” Handbook of Business Strategy, Vol. 6, No. 1, p. 35, 2005.
  2. Pech, R.J., and Slade, B.W., “Maneuver Theory: Business Mission Analysis Process for High Intensity Conflict,” Management Decision, Vol. 42, No. 8, p. 987, 2004.


The authors

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Jonathan Marsh ([email protected]) is corrosion discipline leader for Ionik Consulting and JP Kenny Caledonia Ltd. in the UK. He has more than 20 years’ experience in the field of corrosion and materials, with the last 11 years in support of the oil and gas industry. He has an MS and PhD in corrosion science and engineering from Manchester University and has authored or coauthored more than 40 conference and journal publications.

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Phil Duncan (phil.duncan @ionik.net) is integrity discipline leader and deputy manager for Ionik Consulting and JP Kenny Caledonia Ltd. in the UK. He has worked in support of the oil and gas industry for more than 25 years and joined Ionik Consulting nearly 3 years ago following 14 years with Lloyd’s Register. He currently supports Apache North Sea as its Pipelines Competent Person and Hess Ltd. as subsea integrity technical authority as well as providing ad hoc support to a number of other global oil and gas operators.

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Mark Richardson is subsea projects manager with Apache North Sea Ltd. He has worked for Apache since their takeover of Forties field in 2004 and has project managed their largest topsides and subsea projects. He has an MS in offshore engineering, an MBA from Aberdeen Business School, and is a member of the Association of Project Managers.