Subsea pipelines are vital for transporting offshore oil and gas. Accurate surveys are crucial to understand the pipeline location, burial depth, exposure, and any suspensions. In shallow landing zones, pipelines are vulnerable to tides, waves, and frequent fishing activities. Conventional survey vessels can’t operate here due to shallow depths, leading to a lack of data.
This is where USV come in, with their shallow draft, high flexibility, low fuel consumption, high automation, and no need for onboard personnel, making them perfect for these conditions.
In April 2024, OceanAlpha deployed an L25 USV equipped with a 3D scanning sonar and a sub-bottom profiler. Controlled remotely from the headquarters, the USV surveyed a shallow landing area, mapping terrain and obstacles around the pipeline and checking its route and burial depth.
The survey area is relatively shallow, with a maximum flow rate of 4 knots, and includes a mix of exposed and submerged reefs, which makes it quite complex.
After launching from the dock, the USV was remotely piloted to the survey area 14 kilometers away and successfully surveyed 2 kilometers of subsea pipeline.
The 3D scanning sonar and sub-bottom profiler data results met all required standards. The survey showed water depths around the pipeline ranging from 0 to 8.6 meters, with complex changes due to scouring and maintenance. They marked the gravel area boundaries and surrounding submerged reefs, and the sub-bottom data clearly showed the pipeline’s burial depth.
This project showcased how the L25 USV provided an efficient, economical, and safe solution for underwater survey operations, revolutionizing how we conduct subsea pipeline inspections.