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Reservoir analysis of a CO₂ sequestration site: experiment-guided field scale modeling
Oduwole, Similoluwa
Oduwole, Similoluwa
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2022
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Abstract
The concentration of carbon dioxide (CO2), a naturally existing constituent of the atmosphere, started to rapidly increase from 1800 onwards, marking the beginning of the industrial revolution period. The highest CO2 concentration measured since NOAA started measurements of atmospheric CO2 was reported in May 2021 – atmospheric CO2 increased from 330 ppm in 1958 to 419 ppm in 2021. CO2 is important to monitor because it presently accounts for 80% of the total greenhouse gas emission by the USA. Heat radiated from the Earth is trapped within the troposphere by greenhouse gases, leading to undesirable global warming effects. The Intergovernmental Panel on Climate Change (IPCC) therefore encourages a ‘net zero’ human-caused CO2 emission by 2050 and a reduction of the present atmospheric CO2 content through geosequestration.
Geosequestration is the storage of CO2 in geologic formations. This process requires guided transport to and safety assessment of geologic formations to ensure permanent retention of the injected CO2. Although CO2 saturation maps derived from 4D seismic data have been used to monitor fluid saturation and pressure effects during CO2 injection, they provide no detail of the interactions between CO2 and the components of prior reservoir fluid which influence field processes. Thus, saturation estimates from 4D seismic data are prone to errors based on a lack of knowledge about spatial and temporal fluid coverage.
This research provides a composite workflow to interpret a seismic map from ongoing sequestration into a depleted oil field, using reservoir simulation guided by experimental and well log data. The CMG-GEM reservoir simulation results are interpreted with a flow model to provide insights on the geophysical effects occurring within the formation.
This study shows that injection and producing wells in oil reservoirs respond differently to CO2 injection. It also shows that the mobility of oil components can better explain 4D seismic maps than typical fluid saturation models. Using the reservoir simulation saturation maps alone does not explain subsurface processes. Adding effects of changing fluid mobility of the different oil components from reservoir simulations allows us to better simulate 4D seismic response.
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