Design and Construction of 150-hp ROV for Subsea Production System and Workover Support

ABSTRACT A high powered remote work system was recently designed and built for undersea cable system support which represents the next generation of remotely operated vehicle (ROV) which will be required for Subsea Production System and Workover Support. The paper will provide the details of the design, development, and testing program. INTRODUCTION As subsea production system designs have evolved it has become increasingly evident that the magnitude of the tasks which could be performed by remote work systems for the most efficient installation, long term maintenance, and workover support is beyond the capabilities of most of the existing remotely operated vehicles (ROVs) in existence today. Many of the components which may require replacement over the life of a field in a subsea production system (SSPS) are much too large to be readily accommodated by most of the remote work systems presently in use. The approach to compensating for this mismatch between the relative size and power of existing remote work systems and the corresponding SSPS components has resulted in most cases in overly complex, expensive running procedures and SSPS hardware. A high powered remote work system, the Hydratm AT 1850 CRS, was recently produced for undersea cable systems support which represents the next generation of remotely operated vehicles (ROV) which will be required for subsea production system installation, maintenance, and support. In the configuration for support of subsea production facilities the system is called the Hydratm AT SPS. Rated in its nominal design for 1850m operations, the system design can be easily extended to 3000m and beyond. Its large size, heavy thruster based lift capability, electronic expandibility, and work package accommodation features can greatly increase the efficiency of SSPS support operations and reduce the cost and complexity of SSPS facilities. TECHNICAL DESCRIPTION The Hydratm AT SPS design is based on the Hydratm series of remote work systems which include the following:Hydratm 1000Hydratm2500Hydratm AT 1850Hydratm AT 1850 CRS The cornerstones of the design of these systems are redundancy and reliability. Each of the successive designs in this family of systems provided increased capabilities, improved performance, and improved reliability through a series of technical innovations and operator diagnostic aids. The Hydratm AT SPS is a 150 hp electrohydraulic remote work system. It is designed to be launched and retrieved from the worksite in either of two operational modes depending in the application and the design of the SSPS:utilizing a subsea deployment system; orFree-swimming. For SSPS designs where a vessel is moored overhead or for TLP support, the subsea deployment system provides the best option by minimizing the likelihood of the remote work system umbilical becoming entangled with the risers and/ or tendons. The subsea deployment system is equipped with 200m of neutral tether connected to the vehicle to provide ample excursion distance. For SSPS support where lengthy excursions are required and there are no risers or tendons in which to become entangled the free-swimming mode is the preferred option.