The Use Of Unmanned Remote Controlled Vehicles For Offshore Inspection And Work Tasks

Abstract

Abstract The underwater inspection of offshore platforms, pipelines, marine risers, and support platforms, pipelines, marine risers, and support equipment is a fundamental task associated with the offshore oil industry. For many years these tasks were performed by divers operating from the rig platform or from a pressurized habitat situated on platform or from a pressurized habitat situated on the ocean floor. However, the search for new oil fields has forced operations into more remote locations and into deeper and more hazardous waters. This increases the diver risk factor wad influences the economics of using manned inspection systems. Since the introduction of remote controlled vehicles in 1974, developments in their design and production have dramatically increased the production have dramatically increased the cost-effectiveness of the systems for offshore inspection and work tasks. There are many reasons that an RCV system is economically advantageous for inspection of offshore platforms and pipelines, for location and retrieval of debris, and for monitoring of offshore construction, exploration, and production operations. These reasons include the production operations. These reasons include the RCV's virtually unlimited endurance, its compactness and maneuverability, and its ability to operate in sea states hazardous to men. In addition, RCV's are now equipped with low light level TV cameras, sonar search equipment, automatic depth and altitude controls, wire rope cutters, and manipulator arms with various mission-related tool attachments. During the past 4 years, over 20 remote controlled vehicles have been logging field experience worldwide. This field experience, combined with extensive laboratory research and design analysis have contributed to refinements in the system which maximize its applicability to offshore tasks and continue to increase its cost-effectiveness. For example, one RCV inspected the whole of Chevron's Ninian Platform in 5 days, when 10 days were allotted to inspect only 25% of the massive concrete structure. Similarly, an oil company has estimated that $1.5 million were saved in one year by using the RCV instead of divers to perform inspection and simple work tasks. This paper draws upon such actual RCV operations in the North Sea, Gulf of Mexico, South America, and Southeast Asia and discusses their application to similar offshore operations in the Middle East. New inspection and work techniques made possible by RCV's are discussed; examples of cost-effectiveness are given; and projections for future developments in the field are offered. I. THE ECONOMICS OF OFFSHORE INSPECTION In 1974, a new concept in offshore structure and pipeline inspection was introduced—the remotely controlled unmanned vehicle (RCV). Until the RCV's introduction, video inspection was usually done with guidewire deployed television systems or diver-held systems. Depths were generally not prohibitive, and inspection was usually done only for work verification or damage documentation. As drilling depths increased and structures got older, the need for regular inspection at greater depths became apparent. The large costs involved permitted economical application of higher permitted economical application of higher technology equipment such as the RCV. The RCV-225 is the dominant vehicle system currently being used offshore. Over 20 units have logged approximately 35,000 operational hours in the North Sea, Gulf of Mexico, South America, and Southeast Asia. The vehicle is about the size of a medicine ball and is equipped with a sophisticated low light level TV camera system. It is rated for 2000 meters depth though it is normally supplied with cable sufficient for 400 meters operational depth. Although the vehicle is designed to be launched from a submerged garage, it can be deployed by its small connecting tether from the deck of an oil rig or small boat for shallow water operations.