A Call for Standards in the CO 2 Value Chain Neerup, Randi; Løge, Isaac A; Helgason, Kári ...
Environmental science & technology,
12/2022, Letnik:
56, Številka:
24
Journal Article
Understanding of the processes which take place within a reservoir during and after CO2 injection is essential for successful selection of a storage site for carbon capture and storage. Flow regimes ...that occur when CO2 is injected into a geological formation control how much CO2 can be effectively injected and stored in the formation. This paper presents an experimental investigation of the scaling laws which describe CO2 injection into saline aquifers. Quasi two-dimensional experiments were performed in initially water-filled glass-bead packs to demonstrate the influence of gravitational, viscous and capillary effects on the vertical flow of CO2. The properties of fluids used in the experiments are analogous to the properties of CO2 and brine at possible reservoir conditions. Experiments are performed for a range of dimensionless capillary and CGR numbers which may describe conditions at existing storage sites. The use of dimensionless numbers links the laboratory experiments with the field scale observations and hence these numbers can be applied for the screening of potential storage sites. The experiments represent gravity and viscous unstable floods with fractal-like fronts. The gravity effects were more pronounced in cases with a low injection rate and high permeability, causing less brine displacement. Higher injection rates caused more fingering and increased total displacement.
Within the Skagerrak-Kattegat region up to 14 Mt of CO2 can annually be captured from power and industry sources. To establish a CCS infrastructure in the region it is necessary to identify and ...characterize potential CO2 storage sites. Initial screening of the region has revealed large aquifers in the Upper Triassic Gassum Formation. In dynamic simulation studies 250 Mt of CO2 were injected into the Gassum Formation over a period of 25 years. Identification and analysis of parameters that affect CO2 storage capacity were performed. Parameters important for the migration speed and the dissolution rate of CO2 in open dipping aquifers were investigated by a series of simulations on generic tilted reservoir models.
The Atzbach–Schwanenstadt gas field has been investigated in the CASTOR project with respect to its suitability for safe, long-term underground CO2 storage.
Storage capacity of the reservoir has been ...estimated to 14.5 million tonnes of CO2. Potential nearby CO2 sources emit together about 300 000 tonnes of CO2 per year. Assuming that reservoir would be filled up until its initial reservoir pressure the available storage capacity would be sufficient to store all CO2 produced during the next 48 years. Results from the reservoir simulation of the storage showed that during 30 years of injection 8.2 million tonnes of CO2 could be stored. A CO2-EGR effort in the field could in theory increase gas production and therefore enlarge the available storage capacity for CO2. However, none of the conducted reservoir simulations could prove that CO2 injection would enhance gas recovery at the Atzbach–Schwanenstadt field. CO2 breakthrough to the production wells is very quick and occurs almost immediately after start of injection. The fraction of CO2 in produced gas increases rapidly and this limits production of the clean gas. Compared to the simulation with no CO2 injection, EGR cases give lower production of the clean gas. Therefore use of CO2 for the enhanced gas recovery is not recommended for the Atzbach–Schwanenstadt field.
The long-term storage simulation shows that reservoir pressure stabilizes shortly after injection stops. During the period of 1500 years after the end of injection only 10% of injected CO2 will dissolve in the immobile reservoir water. In a scenario of potential leakage four abandoned wells were selected to mimic leaking wells. Simulation results show that if CO2 reaches the abandoned wells, and this would lead to leakage, as much as 5.6% of injected CO2 could escape from the reservoir during a period of 1500 years.
In this paper an integrated workflow is described for risk assessment within CCS. IFPEN, SINTEF and TNO joined forces to define a comprehensive and transparent risk assessment methodology. The tools ...developed in these institutes are thereby integrated. The workflow can be applied to proposed carbon storage sites. Starting with a qualitative analysis and scenario definition potential risky scenarios are defined. These are subsequently investigated in a quantitative way, either by so-called fast models or by fully developed numerical codes. The scenario analysis includes modelling of the reservoir and caprock behaviour, well integrity evaluation and migration path analysis. The important item of sensitivity analysis is addressed by probabilistic means. Finally, the consequences of potential surface leakage are addressed in this suite, resulting in a clear picture of the risks at a specific site/time. The presented methodology is tested on a real offshore gas field.
Storage of CO2 in deep saline formations is currently the most promising option for mitigating the impact of climatic changes. Therefore, it is important to understand flow processes and distribution ...of forces acting on injected CO2. To demonstrate the influence of gravitational, viscous, and capillary forces on the flow of CO2, special experiments were designed. Laboratory experiments and numerical simulations were performed, where fluid representing CO2 was injected into a 2D porous medium saturated with fluid representing brine. Two sets of fluids characterised by different interfacial tension (IFT) were tested. Results demonstrate that at increasing injection rate viscous forces become stronger, leading to a higher total displacement of brine. Such performance is preferred at field scale, since it facilitates dissolution and residual trapping of CO2. Gravity effects were more pronounced in cases with low injection rates and high permeability and are demonstrated by lower volumes of the in-situ fluid displacement. Therefore, reservoirs giving low influence of gravity forces are more suitable for CO2 storage. The high-IFT fluid system had an IFT corresponding to the value of CO2–brine systems at possible reservoir conditions. However, the fluid flow in the laboratory model was dominated by capillary forces. This kind of behaviour is less likely to be observed at field scale as it is a result of the much smaller volume of porous system used in the laboratory compared to the volume at the field scale. The low-IFT fluid system resembled better field scale flow behaviour. The laboratory experiments were also modelled using a numerical reservoir simulation software. While modelling of observations from high-IFT system was challenging, simulations for low-IFT displacements showed accurate reflection of experiments.
•Experiments that model CO2 flow in porous medium were performed on 2D model.•Effects of capillary, viscous, and gravity forces in fluid flow were demonstrated.•One of the experimental fluid systems had properties analogous to CO2–brine system.•Laboratory experiments were modelled using numerical reservoir simulation software.•Reservoirs with low gravity and high viscous forces were found more suitable for CO2 storage.
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