Tanker loading/unloading lines are unique pipeline assets in the oil and gas industry. In many cases, these pipelines connect shore-based installations to a subsea pipeline end manifold (PLEM). The PLEM is connected to the surface buoy by subsea hoses. The mono-buoy is then connected to the tanker using ﬂoating hoses to accomplish the loading or unloading process. As these lines are the point of export and/or import of hydrocarbons, and in most cases there are no alternative means, they are often deemed a critical element in an operator’s network.
In Asia Pacific, a 40” loading line connecting to a subsea PLEM for transporting crude oil from a local tank farm to sea-going vessels was in need of inspection. The client had initiated a modification of the existing PLEM which would require that part of the pipeline be raised and placed on a structure above the water line. This places significant strain on the pipeline which could further damage existing features. In order to ensure that this modification could be carried out safely, more knowledge concerning the current integrity status of the line was essential. This project presented challenges associated with accessibility, negotiability, and propulsion, specifically:
- Single access to the line from the tank farm area
- Propulsion of the tool in both directions
- The tool had to stop five meters before the wye piece connected to the PLEM
In order to combat the various challenges presented in this case, the ROSEN team utilized the various elements from the Toolbox to customize the optimal solution for the customer. The solution package contained the following elements:
- Bidirectional low-friction 40” MFL unit
- High-resolution MFL technology
- 1.5D back-to-back bend passage capabilities
- Pumps controlling a propulsion medium of treated salt water
- Electronic Tool Detector III (EPD III) read-out consoles
- EPD subsea antennas placed on the pipeline for permanent and undisrupted communication
MFL technology was chosen because it provides ideal measuring performance and it is less susceptible to debris in the pipeline. As the MFL unit traveled through the pipeline, and approached the PLEM, it was detected by the subsea antennas. The salt water pumps, through which the ﬂow was controlled, successfully stopped the tool within 5 m of the wye piece. The ﬂow was then reversed and the inspection tool pushed back to the launcher/receiver station. In spite of unforeseen environmental inﬂuences, such as multiple typhoons, the project was completed as scheduled. The collected data ensured a detailed integrity assessment of the entire pipeline. In fact, multiple anomalies were observed within the critical 500-meter zone before the PLEM. With this detailed information, the client was able to make informed decisions to avoid any incidents.
Minimized Risk Exposure: This solution, oﬀering 100% coverage in one pass, not only saves operational cost, but also oﬀers the highest probability of anomaly detection, allowing the operator to engage in an asset integrity management program.
Increased Uptime: Inspecting loading lines must occur in a timely and efficient manner due to their vital positioning within distribution networks. The solution applied in this case oﬀers a quick turnaround time as well as a robust and proven technology to ensure downtime is minimized.
Lifetime Extension: The current market situation calls for an even sharper focus on the care of existing and aging assets in the oil and gas industry. In the case of this particular loading line, the main reason for conducting this inspection was to provide required information to ensure the safe rehabilitation of a vital component.