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.