Simulation Study of Cap Rock Performance in Saline Aquifers
Abstract/Contents
- Abstract
- Climate change due to greenhouse gases has become an international concern, and is gaining public acceptance. One of many solutions to reduce green house gases is the sequestration of carbon dioxide (CO2). Proven storage sites are depleted oil and gas field reservoirs, however many large point sources of CO2 are not located near these fields, and the cost to build the infrastructure necessary to transport CO2 long distances is expensive. An alternative solution is to store CO2 in saline aquifers that are located at proper depths and temperature. Saline aquifers are abundantly located below the surface of the earth. These potential storage sites also need to have an adequate seal in place to prevent the CO2 from escaping the reservoir, which if it were to leak to a potable water aquifer can cause significant environmental and health concerns. The focus of this study is a sensitivity analysis to understand the properties the cap rock must have relative to the storage reservoir (saline aquifer), to be a successful candidate as a potential geologic storage site. The study is conducted using the numerical simulator TOUGH2. The simulations examine single injection well of 1 Mt per yr of CO2 for a period of 30 years and observed for another 30 years while the pressure buildup dissipates to near it’s pre-injection level. For this sensitivity study the depth of the storage reservoir is 1.5 km to ensure adequate overburden pressure needed for CO2 to be in its supercritical state. Caprock and reservoir parameters evaluated include the caprock and aquifer permeability, capillary entry pressure of the seal, and the thickness of the storage reservoir and the cap-rock. Performance of the cap rock is evaluated based on the retention of CO2 in the storage reservoir, penetration of CO2 into the cap rock, percentage of CO2 that leaks through the cap-rock, pressure build-up in the storage reservoir, pressure build-up in formation above the cap-rock and the plume size of the CO2. The results of this study conclude that the pairing of seals and reservoirs in geologic storage sites can be determined by the reservoir permeability and the contrast of the seal permeability for the dimensions of the geological storage site used. The permeability of the reservoir is the dominant factor in a successful geologic storage site; it determines the pressure build-up and the size of the plume. The permeability of the seal prevents the migration of CO2, in its supercritical phase or in saturated brine. A contrast of four to five orders of magnitude can mitigate the risk of CO2 leakage. The displacement of brine is influenced by the dimensions of the geologic storage site and the pressure build-up during injection. However, there are some anomalies that arise in high permeability reservoirs, larger amounts of CO2 saturated brine in a large plume increase the amount of CO2 displaced and can cause an increase in pressure during post-injection. The study provides guidance for what makes a suitable seal for a geological storage reservoir.
Description
| Type of resource | text |
|---|---|
| Date created | August 2011 |
Creators/Contributors
| Author | Reyna, Israel |
|---|---|
| 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 |
Bibliographic information
Access conditions
- Use and reproduction
- User agrees that, where applicable, content will not be used to identify or to otherwise infringe the privacy or confidentiality rights of individuals. Content distributed via the Stanford Digital Repository may be subject to additional license and use restrictions applied by the depositor.
Preferred citation
- Preferred Citation
- Reyna, Israel. (2011). Simulation Study of Cap Rock Performance in Saline Aquifers. Stanford Digital Repository. Available at: https://purl.stanford.edu/rg807hs4203
Collection
Master's Theses, Doerr School of Sustainability
View other items in this collection in SearchWorksContact information
- Contact
- brannerlibrary@stanford.edu
Also listed in
Loading usage metrics...