Persistent Unmanned Surface Vehicles for Well and Field Support
Authors: Leroy Francois 
Published: October 2011

This paper discusses the application of a wave energy harvesting unmanned surface vehicle (USV) as a platform for Well and Field Support. Acoustic telemetry between the surface and subsea systems and meteorology and oceanography (METOC) at the air-sea interface are key roles for the USV. The paper will review the concept of the USV, and present field tests of the technology in both acoustic gateway and METOC roles.

As subsea installations expand farther from manned platforms and undersea vehicles become more automated acoustic telemetry and navigation become more critical to successful operations. Likewise METOC data demands are significant for Well and Field development and operations. Typically these missions require fixed moorings, drifting buoys or expensive vessels. This paper presents an entirely new deployment approach. With persistent mobile unmanned platforms mobile communications and navigation networks are feasible and METOC data are more widely and affordably obtained.

This paper draws upon extensive field trials of the Wave Glider USV. The basic concepts of the vehicle and station keeping performance will be presented. The vehicle has endured high seas, open ocean transits and station keeping missions. Trials of acoustic telemetry and METOC deployments will be discussed.

Now that persistent USVs have come to market the economics of deploying acoustic networks above subsea systems have changed dramatically. New operational concepts are now viable. This paper will discuss the viability of subsea communications and navigation networks based entirely on unmanned vehicles. The same holds true for Improved operations at reduced cost can be expected as these concepts reach maturity.

This paper is related to one submitted to OTC 2011 (May/Houston). That paper is focused exclusively on acoustic systems (interaction between subsea and the USV). This proposed paper reviews that but expands upon it to include METOC roles.

Introduction: Unmanned Systems in Meterorological and Oceanographic (METOC) Offshore Support

The collection of accurate meteorological and oceanographic data is a vital component of of building weather forecasts and climate models. This information is widely used across industries such as agriculture, shipping, transportation, construction for operational considerations. The Offshore Oil and Gas Production industry has similar need for accurate data for its operations and often relies on collecting the data for specific operations or geographical locations. The weather monitoring and offshore productions have equaly benefited from the development and advances in measuring sensors and apparatus. The instruments now provide high resolution data and often for long duration. The instruments are often deployed either at the surface of the ocean, in the water column or on the seafloor. Their deployment is often supported by remotely operated vehicles (ROV) and now more commonly by autonomous underwater vehicles (AUV). The use of such robots has enhanced the productivity while improving safety in many aspects of operations.

In making METOC measurements, persistence over long periods of time provides the best grounds for accurate forecasts and models. Persistence over time cannot be delivered by manned vessels for obvious costs and safety considerations. Todate, the favored means of persisten data collection has been with the use of moored subsea or surface buoys or deployement of subsea platforms. Such instrumentation still requires costly and sometimes complexe vessel support for the initial deployment and subsequent maintenance schedules. The expansion of offshore drilling into deeper waters has compounded the difficulty and increased the risks with such operations. Recent autonomous vehicles have recorded long duration in missions sur as the Atlantic Crossing over 7300 miles [1] or a 279 days extended mission in the Pacific Ocean [2], but always in continuous motion forward and rarely in station keeping mode. Thus, in-situ measurments supported by unmanned systems, often come at the expense of duration of the measurement at the same location.