Application of dynamic positioning techniques to working class remotely operated vehicles (ROVs)

There are three principal reasons for the increase in the use of remotely operated vehicles (ROVs) to replace divers for subsea operations in offshore oil and gas production during the past several years. First, there has been an increased emphasis on safety. Second, an ROV and its associated support vessel can be leased for about one third of the day rate cost of that associated with divers to perform the same function. And third, hydrocarbon production is taking place in water depths greater than that accessible by divers. This replacement of divers by machines to accomplish more complex tasks has resulted in the development of more sophisticated intervention equipment and more powerful ROVs. The increase in the complexity of the subsea work coupled with more powerful vehicles has placed greater burdens on the ROV pilot. Much of the fatigue could be reduced by supplying the pilot with better information and control. With a fully developed real time navigation system, a representation of the structure could be displayed on a video monitor with the ROV shown as a moving icon on the screen. A snail´s trail from the ROV icon could also be displayed indicating the location of the umbilical. The navigation task is then reduced to monitoring the video representation and verification of position by observing compass heading, and television or sonar displays. Two specific areas which have been addressed are looked at in the paper: the design of a SONAR-CAD Navigation Package and the implementation of a dynamic positioning system used in conjunction with the Marquest Group EXACT system