Monviro 4D gravity surveying technology for accurate CCS monitoring

Carbon capture and storage (CCS) is essential for achieving emission reduction targets. While CCS is not an alternative to electrification or renewable energy sources, it is a necessary tool for removing emissions from sectors that are hard to decarbonise. However, CCS involves environmental risks such as CO₂ leakage, and accurate monitoring solutions are needed to ensure the safe injection and sequestration of CO₂.

Monviro delivers surveying technology for 4D gravity measurements at the seafloor. The data collected shows subtle gravitational changes in subsurface conditions, which is important for the safe planning and implementation of CCS. For example, the technology maps fluid movements, quantifies mass changes in the subsurface, and maps reservoir properties such as permeability.

The Monviro solution generates highly accurate data, orders of magnitude better than what can be obtained by ship or airborne gravity measurements. Acquisition of 4D gravity provides direct measurements of mass change, facilitating more quantitative interpretation than seismic monitoring in this regard. The technology also provides seafloor subsidence measurements with an accuracy of a few millimetres, which is crucial for monitoring the evolution of the pressure plume during injection.

The 4D gravity solution costs down to 10 per cent of a seismic survey, thanks to simpler instrumentation, lower vessel costs and a shorter turnaround time from data acquisition to application.

Moreover, 4D gravity is a passive method of measurement, making it completely safe for the environment, including for fish and marine mammals.

The Monviro solution is flexible as well. Apart from small concrete fundaments, no permanent instrumentation at the seafloor is required. The survey region can therefore be expanded based on the evolution of the CO₂ plume.

Reliable, cost-effective methods for measurement, monitoring and verification (MMV) of CO₂ storage are needed to meet regulatory requirements and ensure that CCS can become a viable industry.

Monviro’s target market is CCS operators, with a special focus on offshore applications for CO₂ injection, both in depleted gas fields and in deep saline aquifers. Originally developed for the oil and gas industry, the technology is well proven and has been used to monitor the CO₂ plume at the Sleipner gas field.

Other potential applications include monitoring the stability of the bathymetry around seafloor installations such as communication infrastructure or offshore wind turbines.