Pipeline reversals and conversions: case studies and best practices.
But the sudden abundance of oil and natural gas is putting pressure on North America's existing pipeline infrastructure, which simply cannot cope with this additional demand. This pressure is compounded by the fact that most of this new oil and gas production is happening in regions not currently served by the existing pipeline infrastructure (Figure 1).
Before the Marcellus boom, for example, Pennsylvania and West Virginia relied largely on natural gas from the western and southwestern U.S. In recent years, however, increased local production has resulted in a supply of gas that is more than sufficient to meet current local demand, with plenty left over to ship to other U.S. states and to Canada. Similarly, the recent oil boom in Canada has resulted in the need to ship large amounts of Canadian oil south to the vast refinery complexes along the Gulf Coast.
As a result of the increase in demand for North American oil and gas shipping, once-uncommon flow reversals and the reuse of existing pipeline assets have become fairly routine for operators, with large incentives being quoted, such as $10-15 million in additional earnings for just one pipeline reversal--Tesoro Logistics LP.
In recent years, for example, gas capacity shipped in pipelines has risen significantly along with the growth in shale production (Figure 2).
One of the most important aspects of pipeline reversals is risk assessment. Many of the pipelines undergoing reversals are older and were manufactured using outdated processes, materials or design elements that aren't acceptable by today's standards. Operators need to perform thorough assessments to determine how risks can change when an older pipeline is reversed or repurposed.
Due to a couple of well-publicized reversal failures, the public is all too aware of what can potentially go wrong with a pipeline reversal. In March 2013, a pipeline leaked about 200,000 barrels of oil near Mayflower, AR. In September 2013, a 20-year-old pipeline spilled over 800,000 gallons of oil in Tioga, ND.
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These failures often overshadow the many successful pipeline reversal over the years. Unfortunately, success stories rarely make headlines. But the truth is that, when completed carefully and after a thorough risk assessment, pipeline reversals can be safe and effective.
Longhorn Reversal, 2001
The original Longhorn Pipeline System comprised of 18-inch and 20-inch pipelines--was built to ship crude oil from Crane to Baytown, TX in 1949 and 1950. In 1998, the line was converted to refined products service with the addition of pumps, terminals and new pipeline segments to transport product from Houston to Odessa and El Paso.
To manage and reduce risks, Longhorn Partners Pipeline went above and beyond the requirements at the time and followed industry best practices for conversion. In 2001, Longhorn Partners (later Magellan Pipeline Company) began a project to again reverse the flow of the Longhorn Pipeline, from Crane to Houston, to transport crude oil.
Looking again to best practices, Longhorn produced the Longhorn Mitigation Plan, with 40 mitigation commitments covering management programs, risk-management processes and integrity issues.
Centennial Conversion, 2001
This huge project involved converting 700 miles of 50-year-old, large-diameter pipeline running from South Texas to the Midwest. The pipeline was built to transport natural gas, but when demand for natural gas declined and demand for petroleum products increased, the joint owners of the pipeline--CMS Energy, Marathon Ashland and TEPPCO--began a conversion project.
The project began with major reviews of the pipeline's condition and history, including:
* Laterals and connections
* Piggability and line cleanliness
* Right-of-way conditions
* Existing threats, such as corrosion or mechanical damage
* Potential threats, such as fatigue
* Equipment required for conversion
* Inline inspection (ILI) and hydrotesting
As a result of this thorough planning, the Centennial Pipeline owners completed the conversion while ensuring maximum pipeline integrity and performance, and minimal customer interruption.
Enbridge Line 9 Reversal, 2014
Enbridge, Canada is planning to reverse an existing oil line, Line 9, between North Westover, Ontario and Montreal, Quebec. The plan is similar to the Longhorn reversal as this will not be the first time this line has been reversed: Line 9 was originally built in 1976 to supply Quebec refineries with western Canada crude oil.
In 1998, the line was reversed to take imported oil from the United Kingdom, West Africa and the Middle East. Now that western Canadian oil is cheaper than the imports, Line 9 will be reversed again.
What's also interesting about this reversal is the amount of public communication involved in the project that Enbridge made information available to the general public. Available information includes a website (http://www.enbridge. com/line9), as well as a brochure detailing the how, when and why of the reversal.
Of course, these are just a few examples of recent projects. Figure 3 shows the reversed and repurposed pipeline has been steadily increasing since the late 1990s.
What Do Regulators Think?
In an effort to establish best practices and safeguard against failures on reversed and repurposed pipelines, regulatory organizations worldwide are beginning to release standards and recommendations. In the U.S., the Pipeline and Hazardous Materials Safety Administration (PHMSA) has issued guidance on pipeline flow reversals, product changes and conversion, alerting U.S.-based operators of the potential impacts.
Though the new guidance is not prescriptive, except when the cost to make these changes exceeds $10 million, PHMSA strongly encouraged operators to submit a comprehensive written plan before beginning a conversion or reversal. PHMSA also advised operators to review their existing integrity plans and be prepared to demonstrate how any additional or increased risks are mitigated.
In addition to issuing new guidance, PHMSA suggested some pipelines are simply not candidates for reversal or conversion, including:
* Grandfathered pipelines with incomplete test or historical data.
* Low-frequency electric-resistance-welded (ERW), lap-welded and unknown seam-welded pipelines.
* Pipelines with a history of failures.
* Pipelines with a design factor of greater than 72% specified minimum yield strength (SMYS).
* Conversions involving volatile liquids.
The recent PHMSA guidance provides valuable recommendations for reversing or repurposing a pipeline.
Canada's National Energy Board (NEB) doesn't have regulations pertaining to reversals or conversions, but there is a thorough review process that considers all stakeholders, garners their objections, and allows the operator to demonstrate compliance through publicized mitigation strategies.
The main issue appears to be that the reversal calls into question the original need and current design of the pipeline. This is largely a political/economic argument, but it has recently generated media attention.
In the United Kingdom, for the revalidation or uprating of a pipeline under the Pipeline Safety Regulations, the operator must provide technical and safety justifications to the UK Health and Safety Executive (HSE) to demonstrate that the pipeline and associated facilities are "fit for purpose." Though not a reversal or re-utilization regulation, the HSE clearly spells out the considerations that would also apply to those types of projects.
Despite a few well-publicized failures, there have been many successful pipeline reversals and conversions, and organizations worldwide are compiling guidelines for safety and best practices. So, what are the lessons learned? What approaches and practices can help ensure the safe completion of such projects?
Most successful case studies share a few common elements:
* Threat assessment: A valuable way to assess all the risks--and how they would change under the new operating conditions--is to conduct a thorough threat assessment and develop a mitigation strategy.
* Documentation review: Gathering documentation sounds relatively easy, but the paperwork for older pipeline often gets lost or destroyed. Material records seem to be the most valuable, as they provide information about pressure rating. If no documentation is available, it's now possible to conduct in-situ positive material identification (PMI) without expensive laboratory testing.
* Inspection: Once threats have been assessed, it is important to determine the criticality of the defects that may exist. Inline inspection is by far the best practice, with technology such as the multiple dataset (MDS) inspection platform able to detect and characterize most anomalies.
* Communication: Keeping all stakeholders informed becomes an absolute imperative. Enbridge's Line 9 reversal is a good example of how social media can be used to communicate project benefits and confront issues.
* Laterals and Connections: The majority of guidance and case studies relate to the main transmission pipeline. But it's important to remember the connections that may not suit the new service. In this case, reconnections may be necessary. Hot tapping and bypass can ensure that this can happen without disruption to customer connections.
Preparation is Key
Probably the most important element in pipeline reversals and conversions is proper preparation, including testing and inspections that can help determine whether the pipeline is fit for the job. There are several inspection and testing methods available; each can help provide a more complete picture of the pipeline.
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Hydrostatic Testing: Hydrotesting was introduced over 60 years ago. It was developed as a direct response to failures in the 1960s resulting from air- or product-based pressure tests. Though hydrotesting offers some advantages over air or product testing, this method has several drawbacks.
While hydrotesting is considered to be the final test for the strength of a pipeline that may be undergoing a reversal or conversion, it is disruptive and does not offer a full picture of potential issues. Hydrotesting really only gives an assurance of integrity on the day testing is conducted. Defects that are close to failure may not be detected during testing, meaning that they will remain unaddressed until they fail at some point in the future.
Inline Inspection (ILI): This is an extremely valuable tool in proving pipeline integrity. There are many tools available for the assessment of a variety of defects, and as computers, storage, and batteries have improved, these tools have only gotten better.
Today, MDS tools (Figure 4) can help operators address multiple threats at one time. Running these tools is becoming common practice for integrity management and is almost a requirement for line reversals or conversions.
Positive Material Identification: Paper-based records for older pipelines are often misplaced, lost or destroyed. What may seem disastrous becomes manageable thanks to new methods that use a combination of in-situ strength and chemical-composition tests to determine a pipeline's material properties. These methods can be linked to sensors on ILI tools using a low field magnetic array to determine material changes.
Leak Detection: Leak detection becomes more important when pipelines change service, especially when the line is carrying new product. Historically, most leaks have been detected by the general public, but there are now more sophisticated solutions available that use fiber optics or airborne survey equipment to detect leaks before they become public incidents.
Until recently, many operators looked at leak detection as a last barrier of defense. After recent failures, though, there has been a push for zero loss, which means moving to safety standards more focused on personal safety and--much more importantly in the oil and gas arena--process safety. Hence, detection and mitigation are preferred.
Emergency Preparedness: Though every step can, and should, be taken to mitigate all threats, there are some situations that just cannot be foreseen (so-called "acts of God").
To guard against the unexpected, emergency-response plans and equipment need to be well-thought-out. For example, one major finding from a recent incident in the Gulf of Mexico was that the emergency-response plan was inadequate and crisis-management training was lacking. In all cases, ensure that every threat is considered in advance. Do not rely on one barrier to prepare for the worst.
Key to Safe Reversals
It is not uncommon to find 60-year-old pipelines operating in excellent condition--as long as they have been maintained, inspected and repaired as required.
Materials, welding, construction, operations, maintenance and emergency-pre paredness knowledge have all improved in the half-century since many of these lines were installed. But if we continue to make improvements and leverage new and better materials and technology, there is no reason that these pipelines can't last another 50 years in their converted form. P&GJ
By Mike Kirkwood, Director of Transmission Market Development, T.D, Williamson, Tulsa, OK
Mike Kirkwood, Ph.D., has more than 25 years of experience in the nuclear, power generation, water, and oil and gas industries. He is a SME in all forms of structural integrity, specializing in pressurized pipelines, and is the author of numerous papers on pipeline integrity, risk, inspection, and repair and rehabilitation.
Figure 3: Pipeline Reversals and Conversions reversals conversions 22 COMPLETED 4 18 (1997-2014) 23 PLANNED 20 1 (2014-2017) Source: Energy Information Administration
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|Author:||Kirkwood, Mike; Williamson, T.D.|
|Publication:||Pipeline & Gas Journal|
|Date:||Sep 1, 2015|
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