Gravity sensors could aid hunt for new oil and gas deposits

Gravity sensors designed for satellites and adapted for use underwater could aid the hunt for new oil and gas deposits.

Researchers at Aberdeen University are converting technology originally developed for use in space so it can scan the seabed to detect changes in gravity, caused by the different density of oil and gas compared to the surrounding rock.

Airborne surveys already use conventional accelerometer gravity sensors to find hydrocarbon deposits, but deploying the more sensitive new technology closer to the seabed using underwater robots could help locate much smaller reserves.

‘The technology itself is compact, robust and low power so it already has inherent advantages for subsea use,’ lead researcher Prof Charles Wang told The Engineer.

‘But subsea is actually more challenging than space because the pressure is much higher and there is also a greater autonomous requirement. You can control the sensor with microwaves in space but in the sea no radio waves can get through to it.’

Traditional sensors measure how gravity affects the movement of a mass on a spring or suspended by magnets, based on principles of classical mechanics. But the new technology, referred to as a cold atom trap, makes use of quantum physics.

Rubidium atoms are cooled to temperatures of near absolute zero until they begin to behave more like waves, effectively acting like a laser beam. Their movement is also affected by gravity in a way that can be measured more accurately than normal lasers.

The technology is so sensitive it could even be used to find faults in underwater pipes, said Wang. ‘It can find gravitational anomalies that could be due to structural failure. We would provide a non-obtrusive technology that could potentially cause much less disruption than traditional methods.’

Wang and his team developed the cold atom trap in a project with the Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory in order to improve satellite gravity sensors used to study the substructure of the earth’s crust.

The researchers worked with subsea specialist Fugro Subsea Services and Trident Underwater Engineering (Systems) to create a proof-of-concept underwater device and are now looking to develop the lab-tested system into a prototype for ocean use.