Estimating Aquifer Properties from High-resolution, Time-lapse Fluid Thickness Measurements at the Sleipner Carbon Capture and Storage Project, North Sea
Abstract
At the Sleipner carbon capture and storage (CCS) project in the North Sea, approximately 1 Mt yr-1 of CO2 is stored at 1000 m depth. Once in the subsurface, the CO2 rises buoyantly through the saline reservoir. Time-lapse seismic images have revealed that the CO2 is trapped in 9 distinct horizons within the reservoir. Recent re-interpretation of the time-lapse seismic images has allowed measurements of the thickness of CO2 in the shallowest (9TH) layer to be obtained with 0.5 m resolution. These snapshots of the spatial distribution of CO2 at different time-steps provide the information needed to understand the flow of CO2 in the subsurface, and extract high resolution spatial information about the aquifer sampled by the top of the CO2 plume. The spreading of CO2 along the variable topography of the aquifer-cap rock contact is well approximated by a porous gravity current. Simple forward models show that the majority of the observed propagation of the CO2 in the Sleipner field can be described by buoyant flow along a variable topography. Using this relatively simple gravity current model, the depth-integrated reservoir and fluid properties and their spatial variation throughout the aquifer are estimated using an inverse technique based on the flow of a porous gravity current and constrained by the seismic observations. We test our results by forward modelling the flow of CO2 in subsequent years using our estimates of the aquifer permeability structure and caprock topography. The results of this inverse technique are used to interrogate the key physical processes responsible for the observed shape and extent of the CO2 layer at Sleipner. Understanding the relative importance and influence of these physical processes on the migration of CO2 in the subsurface has important implications for the appraisal of future CCS sites.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.H31D1412C
- Keywords:
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- 1829 Groundwater hydrology;
- HYDROLOGYDE: 1835 Hydrogeophysics;
- HYDROLOGYDE: 1849 Numerical approximations and analysis;
- HYDROLOGYDE: 1873 Uncertainty assessment;
- HYDROLOGY