AUV gauges electrical potential of subsea pipelines offshore Japan

Japan’s Kawasaki Heavy Industries and French energy major TotalEnergies have completed a joint offshore verification test measuring the electrical potential of subsea pipelines during close-range inspections using an autonomous underwater vehicle (AUV).

The test was performed using what is said to be the world’s first AUV with a robot arm for subsea pipeline inspections, named SPICE (Subsea Precise Inspector with Close Eyes), in Japan, offshore Awaji Island, Hyogo Prefecture.

In a 2020 verification test, conducted under the Joint Technological Development Support Program for Offshore Oil and Natural Gas Fields of DeepStar and The Nippon Foundation Ocean Innovation Consortium, the 5.6-meter SPICE achieved stable pipe-tracking performance, demonstrating high capability as a platform for close-range subsea pipeline inspections.

Following this outcome, Kawasaki decided to launch a joint research project proposed by TotalEnergies to integrate the French company’s electrical potential measurement technology Light Touch Cathodic Protection (LTCP) with SPICE to make the AUV capable of measuring the electrical potential gradient of a pipeline allowing the detection of potential coating defects.

Starting in October 2020 and lasting through February 2021, the basic design was completed and integration simulations were performed. Beginning in August 2021, a more detailed design and modifications of SPICE were conducted to incorporate the LTCP.

According to Kawasaki, these preparations made possible the verification test off Awaji Island from 30 August through 2 September, resulting in the successful measurement by LTCP integrated with SPICE of the electrical potential of pipelines.

First, for this offshore test, simulated pipes and a corrosion protection system were placed on the seabed. SPICE performed the measurements using the robot arm with its newly-integrated measurement device to check the pipelines’ state of protection against corrosion inferred by the measurement of the electrical potential.

The outcome suggests that SPICE can achieve automation and reduce operational time in close-range subsea pipeline inspections currently performed by remotely operated vehicles (ROVs), including measurement of electrical potential, the Japanese company concluded.

“LTCP had demonstrated its repeatability of establishing the effectiveness of the cathodic protection system in a controlled test environment, and there was a need to deploy the technology in close proximity to the pipe under inspection. SPICE with the ability to deploy sensors at a controlled distance, enabled LTCP to demonstrate repeatable performance,” said Andy Gower, R&D Subsea Robotics Project Leader of Stavanger Research Centre at TotalEnergies.

“The potential for additional sensors to be deployed at the same time, should enable other non-destructive test sensors and techniques, providing enhanced data of aging pipeline and allowing integrity threats to be assessed with more detail. The future trend of subsea robotics is for highly maneuverable sensor platforms, and the performance of LTCP integrated with SPICE, provides an effective solution to determine the performance of the cathodic protection system in an operational context.”

Kawasaki received an order back in 2021 from the UK’s Modus Subsea Services for the first commercial model of SPICE, which will be an upgraded version of the one that was used for this verification test.

The company is currently working on production and tests for its commercialization.