A Stability Criterion for the Negative Compressibility Problem in Geothermal Simulation and Discrete Modeling of Failure in Oil Shale Pyrolysis Process
Abstract/Contents
- Abstract
- This report includes two distinct parts: `A Stability Criterion for the Negative Compressibility Problem in Geothermal Simulation` and `Discrete Modeling of Failure in Oil Shale Pyrolysis Process`. The first part analyzes the negative compressibility problem in geothermal simulation, which was conceived and preliminarily analyzed by K. Coats in 1980. He found that although a fully implicit scheme is applied, a conditionally stable behavior still happens in some processes with a real `negative compressibility`, such as the steam flooding process. In analogy to the nonlinear compressibility designed by Coats in a single block steam/water problem, we derive a linear compressibility from the linearized pressure equation. We analyze the behavior of these compressibilities and convergence under different timestep size and initial guesses. Different from Moncorgé and Tchelepi`s argument that the unstable behavior in negative compressibility problems relates to the different sign of linear and nonlinear compressibility, we find that the instability is a more direct result of negative pressure value generated during the iterations. Based on this analysis, a new timestep criterion is proposed, and an improved algorithm is developed. Then, we verify this algorithm in a one-dimensional test case, where the cold water injects into a fully saturated steam reservoir. In the second part, we develop a workflow to translate the actual rock tests to a well-posed simulation problem for using lattice and discrete element hybrid model (L-DEM) developed by R. Affes (2015). In this report, we provide a complete example of the conventional triaxial rock strength test using this workflow. Then, the results are compared with experiment data to validate the model. The lattice/discrete element hybrid method is flexible and extendable for modeling failure in oil shale pyrolysis process. To model the entire oil shale pyrolysis process, a coupled thermo-mechanical-fluid dynamic modeling is needed, and it will be based on the extension of L-DEM.
Description
| Type of resource | text |
|---|---|
| Date created | March 2016 |
Creators/Contributors
| Author | Wang, Yifan |
|---|---|
| Primary advisor | Tchelepi, Hamdi |
| 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
- Wang, Yifan. (2016). A Stability Criterion for the Negative Compressibility Problem in Geothermal Simulation and Discrete Modeling of Failure in Oil Shale Pyrolysis Process. Stanford Digital Repository. Available at: https://purl.stanford.edu/kz462sg7849
Collection
Master's Theses, Doerr School of Sustainability
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