Assuring Integrity of CO2 Storage Sites Through Ground Surface Monitoring (SENSE)

Abstract

The ultimate goal of SENSE is to offer storage site operators a cost-effective monitoring option that can form part of an effective site assurance/monitoring program and feed into workflows for an early alert system to detect unexpected changes in the subsurface.The SENSE project has four demonstration sites for monitoring technologies and developing concepts and procedures. These sites are both onshore and offshore. The onshore sites include In Salah (Algeria) and Hotfield Moors (UK). For these sites, the project will use satellite data to explore the response of the surface to pressure changes in the subsurface. Algorithms for automatic satellite data processing to facilitate quick access to ground elevation data for site operators are under development at the British Geological Survey (BGS) and Norwegian Geotechnical Institute (NGI). The offshore sites include Bay of Mecklenburg (Germany) and the Gulf of Mexico (USA). In addition, the SENSE partners have requested access to data from the Troll Gas Field, the North Sea, to study its subsidence due to production-related pressure reduction. The Troll Gas Field is located next to the storage site considered for the Norwegian Long Ship project, and its data will provide a good understanding of the geomechanics of the area.In this paper, we present the work on the In Salah and the Bay of Mecklenburg sites. New InSAR data from the In Salah are used to evaluate the ground movement during the post-injection period and thus to assess the behaviour of the storage site after completion of the injection phase. Bay of Mecklenburg is an offshore site for field experiment to inject a gas underground, build-up pressure, uplift the seafloor and measure the resulted uplift. The first field campaign at the Bay of Mecklenburg was completed in late 2019. It provided both gravity cores from the seabed and geophysical data acquisition for characterizing the shallow subsurface layers. The gravity cores were characterized for physical and mechanical properties. The material properties were used for simulating injection and response of the seafloor to induced pressure. Geomechanical 2D and 3D simulations show that the reservoir may sustain very low overpressure before it fails. Hence, this magnitude of overpressure may create a seafloor uplift of about a few millimeters to a couple of centimeters. The monitoring techniques are therefore being designed to capture uplift in this order of magnitude during the injection operation.

Cross-domain fusion in smart seafloor sensor networks

“…Extending injection rates towards a degree sufficient to contribute to global CO2 emission budget requires the implementation of novel, cost-efficient monitoring strategies since current reservoir performance and leakage detection monitoring builds on three-dimensional (3D) seismic surveying, which can only be repeated in multi-year intervals and are difficult to scale. However, cost-efficient fiber-optic cable and seafloor lander-based monitoring techniques are currently in development [12]. These allow continuous monitoring of seafloor deformation as proxy for fluid migration in the underground, but require repeated ground truthing using seismic data and need to be calibrated by geomechanical and fluid flow simulations [12].…”

“…However, cost-efficient fiber-optic cable and seafloor lander-based monitoring techniques are currently in development [12]. These allow continuous monitoring of seafloor deformation as proxy for fluid migration in the underground, but require repeated ground truthing using seismic data and need to be calibrated by geomechanical and fluid flow simulations [12]. These data domains are highly uncorrelated and require cross-domain fusion to enable actual data fusion and mining.…”