In the current market climate, operators are looking for ways to extend the life of their existing assets beyond their original design life to reduce future capital expenditures.
A remaining life assessment through inline inspection is a key component when looking to extend the life of a pipeline. ROSEN was challenged to provide an inspection solution for a pipeline in the North Sea to support its life extension.
The 16” pipeline had not been inspected during its 20-year operating life due to challenging pipeline construction, operating conditions and lack of infrastructure. The particular challenges included:
· Deployment of inline inspection technology into the multiphase medium while keeping the system online
· The impact of pipe-in-pipe construction on the pipe saturation for MFL technology
· The effect of low operating pressures (15 – 20 bar) on ILI tool dynamics
· Corrosion-resistant alloy (CRA) cladding and heavy-walled sections (> 25 mm)
· ILI electronics’ functionality in the high-temperature production fluid (> 75°C)
· No pig trap or tie-in at receiving platform
· Limited external inspection data to appraise pipeline condition
· Wax and hydrate formation risks during normal operating conditions
· More than 100 m3 of sand predicted to be deposited in the line
· Limited liquid handling capability at receiving platform
In order to define the inspection goals, ROSEN performed a hazard-based risk assessment to prioritize the pipeline integrity threats and to ultimately predict the expected damage mechanisms. A flow assurance simulation with OLGATM was also employed to predict the likelihood of wax, hydrate, and water formation as well as sand deposition to define pipeline cleaning and liquid handling requirements. Through developing an in-depth knowledge of the client’s operating regime, ROSEN was able to propose a methodology to overcome erratic tool velocity as a result of low pressure by temporarily modifying operating conditions. The performance requirements for cleaning and inspection were then used to perform an initial technology screening and propose a number of viable inspection technology options. These options were then appraised in the context of the available topside infrastructure to propose the optimum cleaning, inspection, and infrastructure solution. After analyzing the costs, benefits, and risks, ROSEN proposed a dual magnet MFL/IEC combination tool as the optimum solution to enable inspection of the high-threat locations while keeping the system online.
ROSEN’s combined expertise in pipeline risk and integrity assessment, infrastructure design, pipeline operations, and inspection technology enabled an integrated approach where technology recommendations were clearly linked to integrity and operational drivers.
The pigging feasibility study provided reliable and cost-effective confirmation of the pipeline’s piggability. Thus, it enabled engineered solutions to be proposed with confidence, removing any uncertainty, and consequently reducing risks during further project phases, including inspection execution and post inline inspection integrity assessment.