Gulf of Mexico riser inspections using a self-propelled ultrasonic solution

Author : Fernando Perez, ROSEN Group

Inspecting offshore risers using in-line inspection technology is a complex operation with inherent risks. However, it is a particular challenge if the risers were not built with standard pigging facilities, such as launchers and receivers, or if the operating conditions do not allow for pigging operations.

In 2024, a major operator in the Gulf of Mexico experienced such challenges when inspecting its risers and therefore approached ROSEN for an alternative in-line inspection solution. The company operates multiple offshore assets in the Gulf of Mexico. These assets include two risers considered to be at risk from external corrosion in the splash zone. As a result, the operator required inspections of the risers for potential corrosion at the splash zone down to the seabed in order to take action to ensure the safety and longevity of these critical offshore assets.

The project presented several challenges that tested ROSEN’s technical capabilities and operational resilience. Conducting operations offshore inherently adds layers of complexity due to the remote location, the harsh environmental conditions, and the need for specialized equipment and logistics. Additionally, free-swimming solutions were not an option because the client preferred to avoid using external equipment such as pumps and vessels for fluid circulation. This constraint required a more innovative and self-sufficient approach. With only one access point available, ROSEN needed to ensure efficient deployment and retrieval of the equipment without compromising the integrity of the inspection. The pipeline’s risers have an exceptionally heavy wall thickness, making ultrasonic testing (UT) technology the ideal approach to ensure the accurate detection and assessment of potential corrosion. Finally, the absence of launching and receiving facilities on the platform meant ROSEN had to devise innovative methods for inserting and extracting the inspection tool.

Given these complexities, ROSEN utilized its wide range of technologies to formulate an ideal approach, selecting the most suitable propulsion elements and the best measurement technology for the asset while ensuring sufficient failsafe elements for the inspection tool itself.

A tethered, self-propelled inspection tool was chosen, capable of independently navigating through the risers without relying on liquid or gas propellants. This tool could be inserted at the platform entry point, eliminating the need for subsea modifications. It would then crawl to the seabed endpoint, where it could be stopped and pulled back by a winch system located on the platform without the need for supporting equipment subsea. This solution allowed the inspection to be carried out without removing the product from the risers and without any subsea work, which minimized potential environmental risks.

Figure 1: Crawler inspection UT tool

The tethered crawler inspection tool (Figure 1) comprised a UT scanner module, a crawler unit for tool propulsion and an odometer segment; it was followed by the trafo and interface units.

The inspection tool was connected to an umbilical winch and a computer system to communicate with and control the inspection tool as it navigated the risers (Figure 2). During operation, the inspection team closely monitored and controlled the tool's movement from the topside. The UT data collected could be viewed live, allowing the on-site analyst to adjust components such as sensor gain to enhance data quality. Additionally, the analyst could perform additional passes over areas of concern to ensure a thorough inspection.

Prior to offshore deployment, ROSEN conducted a rigorous blind-test demonstration at a specialized engineering facility to validate the tool's detection and sizing capabilities. This test was critical in proving the effectiveness of ROSEN's solution under controlled conditions before taking it to the challenging offshore environment. In this demonstration, the engineering facility provided a controlled environment that simulated the heavy wall thickness and other specific conditions of the platform's risers. The crawler successfully detected and accurately sized various anomalies, proving its ability to deliver precise and reliable data. The success of this blind test provided the customer with the confidence that the inspection tool would perform as required in the actual offshore operation.

Figure 2: Complete tool equipment

The inspection was successfully completed in May 2024, providing the client with critical data on the condition of their risers. This project not only demonstrates ROSEN’s capability to handle complex offshore inspections but also reinforces the company’s position as a leader in self-propelled inspections. As a precedent for future offshore inspections, the project shows ROSEN’s ability to develop and implement tailored solutions that can overcome even the most formidable challenges while highlighting the significant role of technology in modern offshore inspections.

Advanced sensor technology, such as the ultrasonic testing (UT) sensors used in ROSEN’s custom-engineered crawler, enables precise detection and measurement of pipeline anomalies. These sensors can penetrate thick pipeline walls and provide high-resolution data, which is essential for an accurate assessment of pipeline conditions. Moreover, the development of self-propelled crawlers represents a major advancement in inspection technology. Unlike traditional methods that rely on external equipment for propulsion and navigation, self-propelled crawlers can move independently within the pipeline. This capability is particularly valuable in challenging environments where deploying external equipment is impractical or risky.

Working closely with the client, ROSEN was able to develop a solution that met their specific needs and addressed the unique challenges of the inspection. This collaborative approach ensured that the solution was not only technically sound but also practical and feasible within the constraints of the offshore environment. Innovation was at the heart of this project. From designing a custom-engineered crawler to conducting comprehensive preplanning activities and simulations, the team continually pushed the boundaries of what is possible in offshore inspections. This commitment to innovation allowed ROSEN to overcome the numerous challenges and deliver a successful outcome for the client.