PPSA Seminar

Ormen Lange is a deep-water (850-1,100m) subsea tieback development off the coast of Norway which produces natural gas and transports it onshore to a processing plant at Nyhamna. Gas to the UK is exported via the 1166 km 42/44-inch Langeled pipeline to Easington in the UK. The development, which been in operation since 2007, consists of 18 wells with 4 subsea templates connected to a 240 km 30inch production pipeline in a looped configuration to enable round trip pigging using gas from Nyhamna. Ongoing risk-based integrity assessment determined in line inspection (ILI) by intelligent pig was due to verify the actual integrity status of the pipeline and was undertaken in Q3 2023.

Challenges included:

• Significant deferment associated with shutting in production for pigging operations requiring flawless planning and execution.
• Multiple key stakeholders requiring to be satisfied the activity was being properly planned and executed.
• Very high amounts of solids expected due to a well sand screen failure which required to be removed prior to ILI.
• Large elevation profile change (1100m) during pig transit to and from the subsea templates and Nyhamna terminal with associated liquid hold up.

Given the challenges, this called for an innovative and progressive approach with all parties working together . The campaign would first start with a high velocity flush of the pipeline using dry gas. This was followed by a Pipeline Innovations’ Pathfinder foam bodied caliper pig which would be deployed to confirm piggability of the pipeline and give information on any potential accumulation of debris.The concern was that a large ‘mound’ of debris could cause a stuck pig; significant amounts of bypass were added as mitigations. Given this concern a cautious iterative progressive pigging programme, was carefully selected. This included the novel use of the ROSEN active cleaning tool which utililises a combination of high differential pressure and the Venturi effect to emit a high velocity jet of product in and around and in front of the pig. Detailed and comprehensive flow assurance modelling for MEG dosage, liquid buildup inbetween runs and pig velocity were applied to all runs. This report demonstrates the approach which utilised a progressive pigging approach and close team collaboration culminating in the flawless proving, cleaning and inspection of the Ormen Lange pipeline.

Pipeline systems experience a range of strain conditions along their length. These are either factored into the pipeline design as known operational strains or as strain resulting from additional external loadings that are potentially unknown during the design or construction phases. Detecting, monitoring, and understanding these additional strains in combination with operational strains are a key part of a pipeline integrity management program. Surveying with inertial mapping tools has been commonly used since the late 1980’s for accurate measurement of bending strain, which unfortunately only provides a part of the picture.

Development of the ILI axial strain measurement tool (AXISS™) was to fulfil pipeline operators’ need for axial strain measurement in combination with available bending strain information to enhance their geohazards risk management programs.

After an extended period of comprehensive field testing and validation, supported by a number of partner customers, Axial Strain Inline Inspection transitioned from a developmental to commercial service more than 10 years ago. Since then, over 25,000 kms (about 15,534.3 mi) of data has been collected with many high strain locations successfully identified and mitigated. And, while axial strain inspection is now established as a proven and important tool for a pipeline operator to assess geohazards and other strain related threats, that experience has provided key insights as to where the current technology strengths lie and of course where we need it to go next to provide the level of information truly needed to optimize our full understanding of strain in the assessment of pipeline threats.

This paper gives a detailed overview of some of those experiences discussed, examples of the applications of the technology, case studies and the types of strain events identified. Secondly, and importantly, this paper provides key insight into the latest developments of the technology that will address the remaining unmet needs of the geohazard and stress engineers tasked with establishing firstly a complete picture of pipeline strain condition and secondly allowing them to effectively optimize any mitigation measures or repair programs.

With the critical role natural gas plays in our energy infrastructure, ensuring the integrity of these pipelines is paramount. This is especially true of river crossings for which External Corrosion Direct Assessment is not possible, In-Line Inspection (ILI) has not been previously possible, and line conditions are not known.

This paper explores the limitations of conventional methods such as manual diving, sonar survey, and traditional free-swimming ILI tools, highlighting their shortcomings in effectively assessing the condition of pipelines at river crossings. Moreover, this paper will emphasise the risks associated with not knowing the integrity condition of the pipeline which include potential leaks, ruptures, and environmental hazards. These risks are heightened at river crossings, where the consequences can be severe and far-reaching.

In response to these challenges and risks, the paper will explore advancements in inline robotic inspection technology which are able to be deployed into and recovered from in-service natural gas pipelines through hot taps installed on the line. This method of deployment avoids shutdowns and service interruptions, while allowing the pipeline operator the ability to gather multiple data sets (visual, deformation, and internal/external metal loss) as the line crosses the river.

The paper will then explore case studies and success stories where robotic inspection technologies have been implemented, showcasing their ability to enhance safety, reduce costs, and minimize environmental impact. By embracing these innovations, operators of natural gas pipelines can proactively monitor and maintain the integrity of their infrastructure at river crossings, ensuring efficient operations and safeguarding the environment for future generations.

In order to begin decommissioning of a12Km Methanol pipeline, firstly the product had to be safely displaced to >99% water. The pipeline configuration is 2 x 6” twin parallel lines > 8” > 16” > 8” > 24” > 12” > 10” > 8” > 6”. Conventional flushing was it estimated may result in the loss of up to 80% of the product (line volume ~1000m3).

Methanol has a commodity spot price, which fluctuates daily (price 18/06/24) $357/m3 meaning up to ~$286K could be lost in the process. Also making for a significant amount of high hazard waste (methanol in water is still flammable to <20% concentration).

In order to mitigate these risks a 40 tonne slug of ice slurry was successfully injected into the line chased by water reducing the interface and increasing product recovery / optimizing waste disposal.

As a result the recovery of on spec product was 670m3 (67%) slightly off spec (still saleable product) was 22% (220m). with the rest of the methanol (11%) being dispersed in 320m3 of flush water.

This is to date the World’s largest single continuous delivery of ice slurry.

A case study for a 14” In Line Isolation Plug, the first use of the technology on Equinor’s Gudrun Platform.

Working to a very tight schedule, STATS modified an existing design to mitigate the risks of precision pigging to the only available, short section of pipe . A controlled pigging operation was essential, and multi-technology tracking was deployed to verify the plugs’ location prior to setting.

The plug provided a fail-safe leak tight double block and monitor isolation, enabling the successful in-situ repair of an ESV during Gudrun’s summer shutdown, keeping the gas pipeline pressurised, saving time, cost and environmental benefits of reduced flaring.

The paper details the development and application of a subsea chemical storage and pumping system required as part of an inline inspection (ILI) operation on a 42” x 890 km gas export pipeline.

The system incorporates subsea storage for 95,000 litres of Tri ethylene Glycol, high flow flushing pumps, high pressure test pump, flow and pressure monitoring, a data logging system, along with mechanical, hydraulic and data ROV interfaces.

The inline inspection requires the installation of a 42” temporary PLR to facilitate launching of a cleaning pig and intelligent Magnetic Flux (MFL) pig from the subsea pipeline manifold to the onshore Liquefied Natural Gas (LNG) plant.

The subsea chemical storage and pumping system removed the need for a subsea downline connecting the support vessel to the high-pressure gas pipeline and enabled large volumes of chemicals to be injected into the pipeline with no risk of gas flow back to the vessel.

In the early 2000's, the research group in DNV (Norway) developed an ILI technology for the inspection of dry gas pipelines (without using a liquid batch). The technology has subsequently been used to inspect over 10,000 miles of operational gas and liquid pipelines around the world.

The authors are presenting a review of lessons learned during the deployment of this innovative technology and reflecting on the advantages and limitations. A summary is presented of validation work completed through pull testing. Field validation is also considered and presented.

Several different use cases are considered; the first being the deployment of acoustic resonance ILI for the baseline inspection of new construction gas pipelines. In particular, a series of newly constructed long-distance gas transmission pipelines that have been inspected using acoustic resonance ILI.

Further, the tools have shown remarkable flexibility in the field of difficult-to-inspect pipelines. Notably, large diameter variations and bidirectional inspections have been performed, as well as very long gas pipeline inspections. Influence of wax on the inspection data is reviewed.

A summary of completed work will be of value to all offshore pipeline operators of challenging pipelines, demonstrating challenging pipeline inspection projects which have been completed successfully.

Despite advancements in ILI technology over the last half century, inspecting small diameter pipelines utilizing ILI tools continues to be a challenge.

Most small diameter pipelines were designed and built without consideration for ILI tool passage. Even so, those that were, may have fittings installed or have operational conditions that do not allow for an ILI tool to navigate the pipeline.

Regardless of developments such as microprocessor computational power, memory density, sensor technology, engineering design, modelling software and rare earth magnetics, applying these advancements in small-diameter ILI tools remains a challenge largely due to space constraints. As a result, many small diameter pipelines have been labeled as ‘unpiggable’.

This paper will describe the design parameters used to develop a new system to overcome the challenges and present several case studies showing real-world applications of this new system.