ROV Pipeline Inspections & Repairs in Subsea Environments
Riley Kooh | June 6, 2022
What is an Oil Rig?An oil rig/oil platform refers to an offshore structure dedicated to the extraction and processing of natural gas or oil. These structures operate nearly identically to a land-based oil drill, however offshore platforms require additional features to function at sea. These include heliports for transportation onsite, living quarters for crew members, and cranes for moving equipment to and from work boats.
The process begins with a 3D seismic survey to identify the location of oil and gas deposits. Once located, wells are drilled thousands of meters for collection, and pipelines are installed to transfer the retrieved oil and gas to processing facilities. Oil tankers can also be used as a primary method of transportation. Once the crude oil or gas is refined into usable fuels, the byproduct is then distributed to filling stations or directly to customers.
Depending on the depth, length, or size of operation, there are a variety of structure styles that can be used for offshore oil and gas.
Fixed PlatformsIdeal for shallow depths, fixed platforms are directly attached to the sea floor. A steel leg design typically is attached to the sea bed via piles or footings, however it is also possible for concrete legs to rely on their weight alone for stability. Fixed platforms are generally chosen for long-term projects where it makes sense to construct a permanent structure.
Self Elevating PlatformsSelf Elevating Platforms are similar to fixed, however they have the benefit of added mobility. Rather than being permanently fixed to the ground, self elevating rigs have built-in moveable legs that can be raised or lowered to temporarily set up a drilling station. Since the rig still operates on physical legs, self elevating platforms are also limited to shallow waters.
Semi-Submersible PlatformsOnce operations require working at depths over 500 meters, platforms that attach to the seafloor are no longer economically viable. A semi-submersible platform uses ballast pontoons to elevate the operating deck far above the water level. The name “semi-submersible” relates to the fact that a portion of the hull structure can be submerged for stability through wave loadings.
Diagram of semi submersible (left) vs. drillship (right)
Drillships, as the name suggests, are large vessels capable of offshore drilling operations. Capable of drilling thousands of meters, drillships offer benefits in portability as well as deep sea operation. Traditionally, drillships were also capable of mooring, however in modern practice, drillships have evolved to use advanced positioning systems to hold station. These systems will control the ship’s thrusters to combat natural forces, however stability is less in comparison to other drilling platforms.
Drilling BargesA drilling barge, similarly to a drillship, floats on top of the ocean surface rather than mooring to the seafloor. Alternatively to a drillship, barges are not pilotable, making it necessary to tow these large floating platforms from place to place. Barges are generally only used for shallow or onshore drilling, since the hull is required to be brought to rest on the seafloor once positioned.
Interested in learning more about all the current offshore platforms? Check out our full article here
Why are Regular Offshore Oil Pipeline Inspections Important?Pipelines made prior to the early 1970s are often considered as aged or old pipelines. Their metallurgical constituents and external corrosion coating effectiveness lower quality in comparison to pipelines of today. According to a recent report from the U.S. Department of Transportation, in 2022 there are still millions of miles of pre-1970s pipe mains being used today.
Many aged structures have suspected weak points and smaller leaks that over time become larger, creating worsening conditions for the structure. Leaks can be massive and catastrophic, garnering a lot of unwanted negative attention. Having an issue like Deepwater Horizon or Exxon Valdez has obvious environmental degradation, public backlash and safety compromises.
By implementing dedicated procedures of regular inspections, issues like suspected weak points or small leaks can be addressed before escalation. Building a consistent portfolio of inspection reports allows for effective asset status monitoring and more economical forecasting of routine repairs. As an end-state, this will result in higher efficiency and increased safety for everyone involved, as well as surrounding areas.
Using ROVs in Subsea Pipeline Inspection and RepairUnderwater ROVs are rapidly becoming the standard for inspections of submerged structures. Highly maneuverable and capable of diving far beyond the capabilities of human divers, ROVs can be used for a variety of GVI, CVI, or DVI inspections. Depending on the working depths or conditions, different classes of ROVs may be required.
Work Class ROV A work class ROV is used for ocean floor exploration and inspections at immense depths that divers are unable to reach. Capable of diving thousands of meters, these massive vehicles require full topside power generation and crane systems for deployment.
Light Work Class ROV A light work class ROV is similar to work class, but at a slightly smaller form factor. Ideal for moderate to deep depths; the ROV is deployed from ships in lieu of divers to explore. It can be used during inspections to make repairs. Large extensions, such as laser scanners or specialized inspection devices and sensors, can be added on.
Observation Class ROV An Observation Class ROV is small in size and easily deployable by hand. They are often used for pre dive checks, conducting visual inspections, and can be equipped with sonar and custom sensors, for versatile applications.
Micro or Mini ROV The micro or mini ROV is the smallest class, often used for simple inspections of hard to reach areas at shallow depths, such as pipe systems and submerged infrastructure. These lightweight and portable devices are easily transported and can still maintain impressive depths up to nearly 700ft.
For optimal economic viability and ease-of-deployment, any pipelines at depths of 1,000ft or less can make use of observation class ROVs. These models generally range between $10,000 - $100,000 USD depending on the features and balance excellent inspection footage with portability. While ROVs may be unable to conduct most repairs, they are an excellent cost-effective tool for monitoring the entire lengths of pipelines. Operators can safely conduct and record inspection footage directly from the platform or off of a small rhib boat.
Aside from pipelines, ROVs can also aid in rig inspections. In open-ocean conditions, free diving can potentially be perilous, making ROVs the ideal solution for quick, safe, and effective underwater inspections. They are commonly used to inspect Hulls, Risers, Legs, Moonpool, Water, Cooling and Ballast Tanks, as well as sea chests.
Benefits of ROV Ownership Over Contracting for Offshore Oil Pipeline Inspection & RepairOwning an ROV not only offers the clear long-term cost benefits over consistently contracting out inspections, it also provides the benefit of control. Coordinating timelines between external companies can be frustrating at best, and catastrophic in a worst-case scenario where a response is needed immediately. Additionally, internal staff are better suited to make informed decisions during visual inspections rather than a contractor with no familiarity of your structure.
Owning an ROV, especially an observation class, also opens up the door for much more frequent inspections. Deep Trekker ROVs set up in as little as 30 seconds, making it feasible to drop in for rapid inspections of a minor concern. Inspections can be day or night, and go on for as long or as short as needed without worrying about tallying costs. Ownership also enables custom reporting of important data for building an inspection history portfolio.
Adversely, inspection companies owning ROVs is a viable option for safer operations and maintaining competitive costs. Being able to have live video feed to show customers with location systems or imaging sonar can be the key differentiators between competitors.
Interested in reading more about the pros & cons of ROV ownership?
The Deep Trekker Difference for Submerged Offshore Pipeline Inspections
Dive to Depths of up to 1,000ftDeep Trekker ROV models are capable of diving up to 1,000ft with full functionality. In past decades, inspections at these depths would have only been possible through massive work-class ROVs like Dimitri Rebikoff’s ‘POODLE’ or the U.S. Navy’s ‘Cutlet’. In modern practice, Deep Trekker’s REVOLUTION or PIVOT ROVs can accomplish these tasks while being deployable by a single operator inminutes.
Extended Mission Times with Hybrid Power or Field Swap BatteriesDeep Trekker has long-been a key name in battery operated ROVs. This design allows for superior portability and rapid setup times, but some may have concerns about extended mission times. Deep Trekker’s REVOLUTION or PIVOT both come with a spare battery set and incorporate a field swap design. With roughly 3-5 hours of battery life per charge, operators can rotate battery sets for endless operation if needed.
Alternatively, for long-term projects where portability may not be beneficial, select models can be integrated with direct power for endless operation.
Rapid Response and DeploymentThe ability to conduct underwater inspections at a moment’s notice is greatly beneficial in maximizing efficiency as operators can quickly respond to potential issues. When answers about a submerged structure are required immediately, being able to deploy in minutes becomes exponentially more valuable.
Advanced StabilizationThe revolving head of Deep Trekker’s REVOLUTION ROV allows operators to rotate the camera, manipulators and sonar all while station holding in moving water. Combined with auto-depth features and active yaw stabilization, a Deep Trekker ROV provides extremely smooth camera performance for accurate surveys.
Integrated High Definition CamerasEquipped with a 4k camera and LED lights, Deep Trekker ROVs provide users with a high quality, live view of the submerged infrastructure they are inspecting. In addition to the real-time view, pilots can take photos and videos for further review and documentation.
Easy to Use and MaintainDeep Trekker ROVs are made with the user in mind. Operators can enjoy the simplicity of unpacking just one or two carrying cases and deploying in minutes thanks to battery power and intuitive engineering. The innovative magnetic coupling at the seals reduces the need for extensive training on how to maintain the ROV, since oiling and/or greasing is not required.
Enhanced Safety and CostConsistently hiring dive teams to conduct underwater inspections not only comes at a punishing monetary cost, but also puts platform workers at unnecessary risk. According to the National Library of Medicine, 228 SCUBA divers died as a direct result from diving in 2019. While ROVs can fill in for divers for a variety of inspections and surveys, repairs may require a dive team. Having an ROV on deck can be extremely beneficial to deploy alongside divers as a method of topside communication.
As always, our team of experts is available to answer any questions you may have. If you’re looking to upgrade your offshore inspections and lower recurring costs, reach out to get your customized quote today.
Industry Related Articles
NASSCO PACP Certification and Inspection 101
August 9, 2021
Established to provide a standardized way of documenting features and defects...
Sonar Systems: All You Need to Know
April 6, 2021
Sonar systems have many applications, but what should you know? This guide...
Water Storage Tank Inspection and Maintenance 101
February 22, 2021
Read on for our step by step guide to basic tank inspection and cleaning with...