Nanoscale Gravity Sensors for Monitoring CO2 Storage

Fundamental to the safe and efficient management of storage of CO2 in geological formations is the ability to monitor the position and amount of CO2. Existing monitoring techniques, although effective at detecting the presence of CO2, have limitations in their ability to make quantitative measurements in the subsurface. The feasibility of using gravity for monitoring of fluid movement in the subsurface has been established through an extensive series of time lapse imaging of water injection into a gascap using surface deployed gravimeters at the Prudhoe Bay oil field in Alaska. However, the depth of rock between the surface and the intervals of interest limits the resolution of the measurements. Greater resolution could be achievable if sensors could be deployed down a borehole adjacent to zones of interest.
The key challenge for borehole gravity sensors has been the development of sensing mechanisms with the necessary resolution and low drift that are capable of miniaturisation. In this project an innovative gravity imaging system is being developed that is capable of imaging a CO2 plume, which can be deployed down reservoir boreholes and which has a resolution similar to surface deployed instruments. This is being supplemented with a new miniaturised gyroscope capable of providing enhanced estimates of 3D position.