A collaboration between Sonardyne International Ltd., Shell and ocean data services provider Liquid Robotics has seen the development of a Liquid Robotics Wave Glider autonomous marine vehicle configured for unmanned data retrieval from seafloor sensors. For the last three years, an array of Sonardyne's autonomous sensors has been recording pressure data for monitoring seafloor subsidence in a Shell-operated deepwater field. Now, using a Wave Glider fitted with a Sonardyne high speed acoustic modem, multiple data harvesting operations have demonstrated the capability to retrieve logged data on demand without the intervention of a conventional survey vessel.
Seabed settlement monitoring is a surveillance tool used to constrain dynamic reservoir models and is undertaken as a part of a comprehensive reservoir surveillance campaign. Changes to the seabed can often be subtle and slow to become apparent so surveillance technologies need to be both precise and repeatable in their measurements to stand any chance of detecting them.
The sensor logging nodes designed and manufactured by Sonardyne operate autonomously and are able to remain deployed for several years without intervention. Depending on the environmental parameters being investigated, a wide range of high precision sensors can be fitted including pressure (depth), temperature, inclination, sound velocity and conductivity. At remotely configurable intervals, each node wakes up, logs and time-stamps sensor data to its onboard memory before returning to standby mode until the next measurement cycle.
The data stored within each sensor node is available for recovery on demand at the surface via the integrated high-speed acoustic modem and during the early stages of the monitoring project, data was conventionally retrieved using acoustic modem technology onboard a vessel of opportunity. However, the new innovative Wave Glider removes the need for such a vessel as it is capable of remaining at sea for many months in all weather conditions, autonomously transiting between each node's location to collect data. "Using a Wave Glider to harvest data acoustically from seabed instruments is a highly economical, and sustainable way to monitor our production," said Paul Hatchell,Geophysicist in Shell's Areal Monitoring research team.
"This method not only significantly reduces the total cost of operations but it also removes the health and safety risks associated with sending a vessel and crew to sea," added Shaun Dunn, Global Business Manager, Exploration at Sonardyne.
"The collaboration to deploy an autonomous marine vehicle such as the Wave Glider means that we can offer clients such as Shell cost-effective and safe methods of collecting subsea sensor data in remote deepwater offshore fields." commented Sudhir Pai, Vice President Operations and Technology at Liquid Robotics Oil and Gas.