Industry under a microscope: improving the reliability and sensitivity of inline inspection tools improves overall pipeline integrity
The oil and gas pipeline industry has been under close scrutiny for a long time. It leads the way as one of the most regulated industries in the world, and for good reason. With so many safety-related, social and environmental factors at stake, comprehensive regulation ensures rigorous standards for the design, construction, operation and maintenance of O&G pipeline systems.
Global economics and political activism also play a role in shaping today’s conversation about pipelines. In North America, public debates about the Keystone XL Pipeline have dominated much of the recent news, compelling operators to vigorously participate in the discussion and advocate their integrity management programs. Although Keystone has been put on hold, social capital can assist in getting projects of this magnitude on the radar again.
Through it all, much of the dialogue has focused on the industry’s commitment to protecting communities and the environment from risk by means of rigorous pipeline integrity management programs. As a result, the requirement for increased pipeline safety drives innovative research into improving the sensitivity and reliability of inline inspection (ILI) tools.
Most operators already deploy trusted inline technologies that detect structural deterioration and help maintain pipeline integrity. However, with pressure mounting from stricter regulation, increased operational costs, commodity price-driven budgetary pressure, and often limited available resources, operators face an increasing number of challenges, including vigilance from highly engaged consumer groups.
Although the pressure to perform is greater than ever, operators are responding appropriately with greater confidence in modern technologies to assist in the operation and monitoring of their pipeline systems.
Better ILI tools instill better confidence in containment
To have confidence in the pipeline, operators must have confidence in the capabilities of ILI tools to detect small anomalies that could lead to potential failures. They must also trust the reliability and interpretation of the data, knowing with as much certainly as possible that the depth, size and location of the pipe wall anomaly is correct.
Overall the news is good. Between 2002 and 2013, Canadian Energy Pipeline Association (CEPA) member companies were able to transport oil and natural gas with a 99.999 percent safety record. While that statistic sounds impressive, headline-grabbing pipeline incidents do occur, (in 2014 there were 122 natural gas and liquid releases) and when that happens, the repercussions can undo years of containment management trust and goodwill.
While the oil and gas industry boasts a remarkable safety record, a reliance on conventional tools limit the near perfect record. As much as the technologies have been refined, regulators have noted that inline inspections don’t pick up all defects, and expedient follow-through often depends on the people analyzing the data and planning repairs, a process that can take months.
“Despite their sophistication, the detection capabilities of inline inspection tools have limitations,” the US National Transportation Safety Board noted in its report on the 3.3-million-liter 2010 spill in Michigan.
Limitations of conventional ILI inline inspection technologies
The oil and gas pipeline industry has access to an extensive toolbox of technologies for robust integrity programs. Some tools address cracks or corrosion issues, while other tools focus on stress, pressure and product containment. Cost, resolution, reliability, data analysis speed – each technology has its own strengths and limitations, with no silver bullet as the single solution for collecting pipeline condition information.
For example, there is a strongly-held belief in hydrostatic testing as a reliable method to test a pipeline’s integrity. One of the earliest inspection techniques, hydrostatic testing determines if a pipeline can hold its operating pressure. A form of destructive testing, hydrostatic inspection involves purging the product, flooding the line with water, pressurizing it to a predetermined level and maintaining the pressure for a period. Based on the results, detected anomalies in pressure, volume and density can be a precursor to leaks.
Critics however, argue and have quite effectively demonstrated that the hydrostatic tests lack the ability to monitor ongoing corrosion or cracking and that the high pressure environment can exacerbate previously small defects, increasing risk of future rupture.
Smart pigs for detecting large cracks and corrosion
Unlike hydrostatic testing, which is often conducted on pipelines for acceptance testing or for pipelines recently rehabilitated, pigging is the more commonly accepted method of testing pipeline integrity.
While newer “smart” pigs have an excellent reputation for accuracy, their efficacy is often limited to detecting corrosion and cracking that exceeds the threshold for detection of the technology. Small corrosion pits and cracks, especially cracks grouped in a colony, can pose a challenge to most conventional ILI pigging devices.
The various ILI technologies are sensitive to axial or circumferential defects, and each has limitation for minimum aspect ratios or cross sectional wall loss area before the ILI tool can report the anomaly. It is also possible to have cracks and wall loss pits that are in close proximity to girth welds, long seams, and other features in the pipe, which can mask the defect, preventing the ILI tool from properly identifying and sizing. As a result, it is possible to have leaking cracks and corrosion pits that are too small to be sized and reported from conventional ILI.
Not all lines are piggable
Some pipes are more suitable for pigging than others. While most oil and gas transmission lines were built in long straight sections suitable for pig runs, sections with small diameter pipe and small bend radius pipe configurations can limit many ILI tools. Lines with expansion loops and miter bends, and in the case of natural gas lines, those with reduced port valves, are factors that can prohibit or restrict the traversing of inline tools.
Mass balance measurement and other leak detection tools
To make up for the limitations of conventional ILI technologies, operators often deploy measurement methods and leak detection technologies to complement their integrity programs.
Mass balance is a means of detecting leaks by measuring the mass of product entering the pipeline compared to the mass exiting the pipeline. The limitation for detecting small leaks is the sensitivity of the mass meters being used (2-4% accuracy for conventional orifice meters and 0.25% for turbine meters), and the fact that the product temperature and pressure changes as it moves through the pipeline.
While mass balance is a means to determine leaks, it is also recognized that making actual measurement of mass from volume (through a meter) at different temperature and pressure going in versus coming out of the pipeline, in real time, is difficult, and not very precise or sensitive to small leaks.
As a result, a leak has to release more product than the total tolerance of the mass balance system before a positive leak/release event is alarmed.
Acoustic leak detection
Minute cracks are often preliminary indicators of potential small leaks that produce acoustic emissions at levels often unrecognizable over background noise.
Acoustic leak detection can be conducted with geophones/hydrophones, comparators and acoustic fiber optic techniques, and each of these acoustic tools is subject to different background noise limitations to determine leak detection thresholds. Not only can these tools have limitations to prevent small leak detection, the expense from installing permanent acoustic systems may reduce the practicality of these technologies.
Emerging technologies on the horizon
To complement hydrostatic testing, conventional pigging tools, and leak detection technologies, the oil and gas industry is evaluating a growing number of emerging external confirmation of containment technologies. These include vapour-sensor systems, hydrocarbon-sensing cables that change in the presence of hydrocarbons, internal pressure wave based tools and fibre-optic based systems that detect temperature changes and acoustic signals associated with leaks.
While these technologies offer hope for more precise surveys, they have yet to be universally accepted or proven. Many are still under development and often require economically impractical installation requirements.
However, there is an innovative, multi-sensor ILI platform that has been used in integrity management programs since 2006, gaining the attention of major pipeline players who have tested the platform, which has now been used on over 25,000 kilometers of pipeline in total.
Introducing SmartBall® technology for Oil & Gas pipelines
To provide a realistic snapshot of a pipe’s condition, many proactive operators are deploying SmartBall technology, a free-swimming multi-sensor tool for long inspections of piggable and difficult to pig liquid and gas pipelines 4 inches and larger. This advantage makes the ball-shaped tool an excellent choice for traversing not just standard diameter pipes, but for smaller diameter liquid lines and for gas pipelines with loops and frequent sharp bends and heavy wall fittings.
During an inspection, the SmartBall sensors collect acoustic, pressure, temperature, magnetic and inertial data from inside the pipeline.
Primary applications for the SmartBall tool
SmartBall surveys can be conducted independently, at regular intervals, as part of a routine pipeline integrity management program, or as a value-add to inspection programs along with hydro-testing, ILI, or direct assessment.
The tool is launched and retrieved at existing pig traps and is tracked using proprietary acoustic receivers and/or Armadillo pig tracking boxes (AGMs). The location data from acoustic receivers and tracking boxes is used during data analysis to locate any anomalies.
SmartBall technology has three primary applications, and the multi-sensor tool can provide a variety of pipeline data.
1. Confirmation of Containment
Regular confirmation of containment surveys are an important part of integrity management as leaks are often a preliminary indicator of pipe failure.
Unlike conventional leak detection systems, confirmation of containment with SmartBall supplements these systems. The SmartBall tool directly passes leaks, and is therefore capable of detecting losses as small as 150 mL/min, which can be several orders of magnitude more sensitive than conventional methods.
SmartBall surveys can also complement regular ILI surveys by addressing potential pinhole anomalies that have aspect ratios below the reporting threshold of ILI systems.
2. Pressure and Temperature profiles
As the SmartBall is rolling and not sealing against the pipe ID, as conventional pigs do, the tool can also record precise pressure and temperature profiles. The SmartBall platform can be deployed in gas pipelines, where pressure and temperature profiles can be integrated into flow models to assess the points where water vapor may condense out of the gas.
The tool can also be used to assess the point where high temperatures from pump or compressor output may have affected the pipe coating, as well as in settings to validate and improve SCADA and mass balance systems.
3. Pipe Wall Assessment and Inertial Mapping
During inspection, the SmartBall Pipe Wall Assessment (PWA) tool collects magnetic data that can provide a screening of the pipe wall for stress resulting from features like large cracks, large wall loss, dents and points of excessive loading. The test can also complement hydrostatic testing, as it can survey the pipeline before and after hydro-tests to identify stress that is indicative of pressure reversals.
In addition, the SmartBall PWA tool can produce a girth weld and joint tally for the pipeline, as well as can confirm locations of bends and general geometry of the pipeline.
Helping operators make better decisions
Admittedly, SmartBall is not designed to compete with high resolution technologies like Magnetic Flux Leakage (MFL), which can provide detailed wall loss data.
What SmartBall can do is complement other integrity tools by providing additional data sets to ensure pipeline integrity. In a single deployment, it can detect anomalies associated with pinhole leaks and stress that doesn’t necessarily involve wall loss; e.g. geotechnical strains. It can also detect change in pressure and temperatures.
Ultimately, the SmartBall tool can help capture enough data to confirm the integrity of the pipe and give operators enough microscopic knowledge to make better, informed, risk-based decisions on the health of their pipelines.