Date of Award

8-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Hydrogeology

Advisor

Falta, Ronald W.

Committee Member

Murdoch , Lawrence C.

Committee Member

Stevenson , D. E.

Committee Member

Brame , Scott E.

Abstract

Characteristic curves used in numerical multiphase flow simulators describe relative permeability-saturation and capillary pressure-saturation relationships for flow simulations. Characteristic curves are typically non-hysteretic; meaning they are monotonic functions of saturation and are limited to a single value for residual saturation. Implications of residual saturation are important for environmental, petroleum, and geologic carbon sequestration modeling. However, hysteretic characteristic curves predict that trapped residual saturation depends on the local saturation history. The use of hysteretic characteristic curves is critical to predicting the residual saturation and ultimately the mobility of a nonwetting phase such as supercritical CO2 or a nonaqueous phase liquid (NAPL). Previous hysteretic formulations often have discontinuous derivatives of relative permeability and capillary pressure at turning point saturations, which can cause numerical difficulties during Newton-Raphson iterations. A straight forward hysteretic model for nonwetting phase trapping is presented and assessed by comparison to both experimental and published simulation results. This constitutive model produces smooth, continuously differentiable relative permeability and capillary pressure curves at drainage-imbibition turning points, which eases numerical performance during the Newton-Raphson iteration technique used to solve the non-linear governing equations used to analyze multiphase flow. In addition, hysteresis is included in the characteristic functions without requiring any additional parameters. An assessment of the new model is made by simulating an experiment published by Johnston and Adamski (2005) that explored the relationship of residual- and maximum- non-wetting phase saturations using an undisturbed soil sample. Another assessment is made by comparing the results of the new model to an analysis by Doughty (2007) when simulating the injection and migration of a supercritical CO2 plume in a deep storage formation. The simulated results compare favorably and confirm that the new model can duplicate essential features of more complicated hysteretic models.

Share

COinS