Electrical Impedance Tomography
Abstract/Contents
- Abstract
- Three-dimensional Electrical Impedance Tomography (EIT) is a technique that has the potential to provide estimates of reservoir saturation at multiple scales by determining the resistivity distribution within the subsurface. In theory EIT is well suited for researching geothermal systems due to the large contrast in resistivity between the liquid and vapor phases. Here in our initial laboratory investigation we have applied the EIT technique to measure the saturation distribution within a core. The initial EIT experiment presented here used a Berea sandstone core with 48 electrodes attached in three rings of 16. The core was open to the atmosphere with saturation occurring by natural imbibition and desaturation by evaporation. The voltage potential field was measured by applying a direct current pulse across the core and measuring the voltage potential at all electrodes, essentially applying the 4-wire resistance technique over all electrodes in turn. The result was a data set that embodies the resistivity distribution within the core, and by inversion the resistivity distribution was reconstructed, which allowed for the inference of the saturation. The data processing was accomplished by utilizing the EIDORS toolkit which was developed for application to this nonlinear and ill-posed inverse problem. The procedure utilizes a finite element model for forward calculation and a regularized nonlinear inverse solver to obtain a unique and stable inverse solution (Polydorides et al. 2002). Experiments have indicated EIT is a viable technique for studying the displacement characteristics of fluids with contrasting resistivity, and is capable of detecting displacement fronts in near real-time. The current system is also a quantitative technique able to measure saturation distributions accurately between 20% < Sw < 65%. These limitations were imposed due to connate water connections to the electrodes and ion mobility effects caused by the DC voltage source. It is anticipated that the applicability of EIT will increase to Sw= 100% with the implementation of an AC voltage source.
Description
| Type of resource | text |
|---|---|
| Date created | June 2006 |
Creators/Contributors
| Author | Stacey, Robert W. |
|---|---|
| Primary advisor | Horne, Roland N. |
| Degree granting institution | Stanford University, Department of Petroleum Engineering |
Subjects
| Subject | School of Earth Energy & Environmental Sciences |
|---|---|
| Genre | Thesis |
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Preferred citation
- Preferred Citation
- Stacey, Robert W. (2006). Electrical Impedance Tomography. Stanford Digital Repository. Available at: https://purl.stanford.edu/gp257mc2364
Collection
Master's Theses, Doerr School of Sustainability
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