In a nutshell
No launching or receiving facilities, lack of adequate propulsion, heavy wall thicknesses and offshore conditions – these are all challenges that can “easily” be overcome. But what to do when the cleanliness of a pipeline is the real issue? This article shows the value of choosing the right technology for the job and the need for adequate cleaning programs prior to in-line inspection activities. Cleaning and maintenance work can dramatically increase the efficiency of a pipeline, but it can also have dramatic effects on the success of other integrity activities.
Solidifying a new partnership in Sarawak, Malaysia, the ROSEN Group successfully tackled yet another bundle of pipeline inspections, including, in this case, a total of five pipelines: two transporting crude oil and one gas- and two water-injection lines spanning from the offshore platform to an onshore receiving terminal. One of the factors making these lines unique is, most significantly, their age: after more than 20 years in operation, they had never been subjected to an intelligent pipeline inspection. As a result, both the operator and ROSEN experts went into the project with little knowledge of what was to come. In addition, challenging offshore conditions meant restricted access for tools and personnel alike.
In order to ensure the best data-collection results and gain valuable insights into the pipelines’ integrity status, a decision was made to deploy ultrasound (UT) measurement technology. UT measurement technology is well accepted by the industry as an established method for quantitative wall thickness measurements and for the detection and sizing of metal loss features. It has been optimized to detect and accurately measure internal and external anomalies such as corrosion; lamination; gouging; pitting; narrow axial, preferential seam weld corrosion; and other metal loss features.
Additional advantages include the low friction forces the technology applies, its ability to detect both axial and circumferential features, and its “slender” nature – which makes it easier to negotiate the inside of the pipeline. In this case, UT was chosen as the most optimal inspection method, primarily due to the presence of high wall thicknesses. However, UT also presents a few disadvantages: the need for a liquid couplant and, a factor that is elemental to this case, the need for a very clean pipeline.
Combining the two factors asset age and technology choice, an aggressive cleaning program was required to ensure inspection success. The true challenge of this project became clear at this point, and it was only solidified when the initial two runs failed because the quality of the collected data was severely affected by the presence of heavy debris in the pipeline. This proved that the previously conducted routine cleaning programs had not been sufficient. The dedicated ROSEN team thus suggested the execution of an aggressive cleaning program encompassing a descaling pig, a bulldozer pig, and a heavy wire foam pig.
As each pig was sent through the pipeline, ROSEN experts monitored the amount of debris collected until zero debris was retrieved. This resulted in almost 20 cleaning runs to ensure the success of the subsequent inspection. Having removed more than 100 kg of iron ferrous sulfide from all five pipelines, not only was the inspection possible and successful, continued operation is now more efficient, and production can continue at an increased level, boosting both the service life and the performance of the pipelines.
Figure 1 – The importance of cleaning demonstrated in a 12" pipeline.
The launching and receiving of the cleaning tools and the subsequent inspection tools presented additional challenges that needed to be tackled, as the offshore conditions meant that neither a launcher nor a receiver was present, making it necessary to install temporary ones. Once the access points were made clear, propulsion became the next concern. The pipeline did not provide the minimum speed of 1 m/s required to carry cleaning tools or ILI tools, meaning a pumping system needed to be deployed. As is the case with most technologies, UT has parameters that provide the most ideal operating conditions. For this reason, it was critical that the speed of 1 m/s would be achieved in order to ensure the collection of high-resolution data. In addition, in the gas pipeline inspection, the UT measurement required a liquid couplant to gather data; therefore, the pumping system was once again implemented using treated sea water. ROSEN experts chose to use treated sea water to avoid any future integrity threats to the pipeline.
Numerous challenges arose in the short two-week time frame in which this task was completed. From access to propulsion to negotiation of tools, various types of solutions had to be delivered. Although the solutions in this particular case all seemed to focus on the operational aspects of the inspection, the ultimate goal is always to collect the highest-quality data possible in order to gain insights into the assets’ integrity status; this was achieved. Looking back on the project, we can say that the importance of cleaning programs and the correct choice of measurement technology are vital. Regular pipeline cleaning cannot only prepare a pipeline for upcoming in-line inspections and, therefore, prevent failed runs, it also can dramatically increase the performance of an asset.