An Experimental Study of CO2 Exsolution and Relative Permeability Measurements During CO2 Saturated Water Depressurization
Abstract/Contents
- Abstract
- Dissolution of CO2 into brine is an important and favorable trapping mechanism for geologic storage of CO2. There are scenarios, however, where dissolved CO2 may migrate out of the storage reservoir. Under these conditions, CO2 will exsolve from solution during depressurization of the brine, leading to the formation of separate CO2 phase. For example, a CO2 sequestration system with a brine-permeable caprock may be favoured to allow for pressure relief in the sequestration reservoir. In this case, CO2-rich brine may be transported upwards along a pressure gradient caused by CO2 injection. Here we conduct an experimental study of CO2 exsolution to observe the behaviour of exsolved gas under a wide range of depressurization. Exsolution experiments in highly permeable Berea sandstones and low permeability Mount Simon sandstones are presented. Using X-ray CT scanning, the evolution of gas phase CO2 and its spatial distribution is observed. Additionally, we measure relative permeability curves for exsolved CO2 and water based on mass balances and continuous observation of the pressure drop across the core from 12.41MPa to 2.76MPa. The results show that the minimum CO2 saturation at which CO2 bubbles mobilize is from 11.7%~15.5%. Exsolved CO2 is distributed uniformly in homogeneous rock samples with no statistical correlation between porosity and CO2 saturation observed. No gravitational redistribution of exsolved CO2 is observed after depressurization. Also, significant differences exist between the relative permeability of exsolved CO2 and water and the relative permeability derived from steady-state core flooding experiments. Specifically, low relative permeabilities of both CO2 and water are measured, even when the CO2 saturation is as high as 40%. The large mobility reduction is considered the result of disconnected gas bubbles in this two-phase flow system. This feature is also thought to be favorable for storage security after injection.
Description
| Type of resource | text |
|---|---|
| Date created | June 2011 |
Creators/Contributors
| Author | Zuo, Lin |
|---|---|
| Primary advisor | Benson, Sally M. |
| Degree granting institution | Stanford University, Department of Energy Resources Engineering |
Subjects
| Subject | School of Earth Energy & Environmental Sciences |
|---|---|
| Genre | Thesis |
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Preferred citation
- Preferred Citation
- Zuo, Lin. (2011). An Experimental Study of CO2 Exsolution and Relative Permeability Measurements During CO2 Saturated Water Depressurization. Stanford Digital Repository. Available at: https://purl.stanford.edu/xm613qd8168
Collection
Master's Theses, Doerr School of Sustainability
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