Equinor: Custom Solution for an Extreme Subsea Pipeline

Equinor required a baseline surveyMeasurements, inspections, or observations intended to discover and identify events or conditions that indicate a departure from normal operation or undamaged c… of its new Polarled gas pipeline as part of the commissioning process. When working with gas pipelines, inline inspections (ILI) identifying corrosionThe deterioration or degradation of a pipeline caused by chemical or electrochemical reactions with its environment. Corrosion is a significant concern as it ca… are typically completed with magnetic flux leakage (MFL)A type of non-destructive evaluation used on inline inspection (ILI) technology in which a magnetic field is induced in the pipe wall to detect, classify, and c… technology due to the absence of a liquid coupling medium.  However, MFL depth sizing accuracyThe accuracy with which an anomaly dimension or characteristic is reported. is reduced in direct proportion to the pipe wall thickness. This pipeline has a varying wall thickness range of 28.9 mm to 37.5 mm (1.1" to 1.5") which meant that ultrasonic technology (UT)Systems used in non-destructive testing that utilize sound waves to detect, identify, and measure anomalies within a pipeline integrity test or management progr… offered a solution which was up to 80% more accurate for depth sizing. UT inspectionThe systematic process of visually examining, testing, or monitoring pipeline components to assess their condition, integrity, and compliance with regulatory re… was feasible as prior to operation, the pipeline was filled with treated seawater.  Polarled is the first pipeline on the Norwegian continental shelf that crosses the Arctic Circle which brings both operational and environmental challenges. 

The Polarled pipeline is 482 km (299 miles) long and 36" in diameter running from Nyhamna in western Norway to the Aasta Hansteen field in the Norwegian Sea. The key operational challenge was that the ILI tool could not be pumped in one go. A series of cleaning pigs were first launched into the line, 25 km (15.9 miles) ahead of the tool but they could not be recovered by the subsea receiverAn ancillary item of pipeline equipment, with associated pipe work and valves, for introducing a cleaning pig or inline inspection (ILI) tool into a pipeline (l… at the same time as the intelligent pigAn instrumented device used for inspecting the internal condition of pipelines. It is a vital tool in pipeline integrity management, providing valuable data abo…. Due to variability in weather conditions Equinor needed the tool to remain powered while waiting for extended time periods. 

To meet this requirement, a modified ILI tool with 470 hour battery life was required, well in excess of the actual expected run time of 270 hours. The main environmental challenge related to the ruggedness of the tool. The field waterAn inorganic compound of hydrogen and oxygen. Used in non-destructive testing as a penetrant and as a medium for testing. depth is 1,260 m (4,133 ft 10") at Aasta Hansteen. This depth combined with the pressure in the line gives an expected operating pressure of 170 bar (2,465 psi). Normally, intelligent ILI tools are certified to 120 bar (1,740 psi) so this required a robust redesign, additional testing and assurance to meet these enhanced limitations.

• Customization to overcome operational and environmental challenges. The project was designed and delivered to meet the operational specifications of this undersea pipeline. A customized tool was fully certified to the harsh operating environmentSurroundings or conditions (physical, chemical, mechanical) in which a material exists. The environment plays a significant role in pipeline design, constructio… to ensure safe operation and a trouble-free project. 

• An exacting dataset to more accurately monitor future corrosionThe deterioration or degradation of a pipeline caused by chemical or electrochemical reactions with its environment. Corrosion is a significant concern as it ca…. This baseline inspectionThe systematic process of visually examining, testing, or monitoring pipeline components to assess their condition, integrity, and compliance with regulatory re… with UTSystems used in non-destructive testing that utilize sound waves to detect, identify, and measure anomalies within a pipeline integrity test or management progr… was collected with the highest accuracy available today. Not only is the pipeline ready for operation but the operatorAn entity or organization responsible for the operation, management, and maintenance of a pipeline system. The operator is entrusted with ensuring the safe, rel… now has the inputs required to improve integrityThe capability of a pipeline to perform its intended function safely and reliably throughout its life. It includes a range of factors, including the structural … management over the lifetime of this strategic asset. Given the accuracy of the data, the baseline manufacturing defects are now known and corrosion growth can be confidently monitored. 

• Excellent project execution and first run successRefers to the completion of a process or operation that achieves the desired outcome or meets the required specifications without the need for any rework, modif…. This carefully designed and meticulously planned inspectionThe systematic process of visually examining, testing, or monitoring pipeline components to assess their condition, integrity, and compliance with regulatory re… was completed with a first-run success. This was important, not only due to support team costs but also due to the oncoming winter and the short window available for the inspection.