Gravitude As

Trond Espedal

Bjarte Fagerås

John Even Lindgård

Yngve Rusås

Lars Hille

Hugo Ruiz

Remy Agersborg

Martin Vatshelle

Louise Wedderkopp Bjerrum

A system () for monitoring a field () under a body of water, wherein the system () comprises a reference station () and a plurality of permanent seafloor sensors (). Each permanent seafloor sensor () is fixed relative to a seafloor () on or at the field (). The seafloor sensor () further has a nearby survey station () sufficiently distant to ensure that a movable sensor () visiting the nearby survey station () does not disturb measurements from the permanent seafloor sensor (). The distance is sufficiently close to ensure that the offset (&#x394;p, &#x394;g) from a value provided by the permanent seafloor sensor () is constant or can be modelled, e.g. to account for changes in the pressure/depth relation due to changes in water density. Each seafloor sensor is associated with a unique drift function d(t) at least comprising a drift rate (a). Thus, each permanent seafloor () sensor provide an output that is corrected for drift at any time between calibration surveys. The system may be used for permanent monitoring of a seafloor.

System and method for monitoring a field

A device () for performing measurements on a seabed (), comprises a chamber () containing a sensor () and a fluid () at a constant temperature and at an ambient pressure. This removes the need for calibration in large ranges of both pressure and temperature. In addition, this eliminates the need to wait until the sensor () has achieved ambient temperature, and thereby achieves a desired accuracy of the recordings from the sensor while decreasing the operation time. The device preferably comprises an insulating layer (), an internal temperature stabilising device () and a circulating device () to ensure a constant temperature and low temperature gradients within the chamber (). The pressure within chamber () may be equalised to ambient pressure by a pressure inlet ().

Device and system for performing measurements on a seabed

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Fyllingsdalen, Norway

Trond Espedal