Simplified One-Dimensional Model for Alkali Surfactant Polymer Floods
Abstract/Contents
- Abstract
- Alkali surfactant polymer (ASP) flood is a promising EOR technique that has been widely applied as a tertiary recovery process during the past years with potentially up to 30% OOIP incremental oil recovery. ASP floods combine the benefits of two interfacial tension reducing chemicals (alkali and surfactant) to improve microscopic displacement efficiency and a mobility control agent (polymer) to enhance macroscopic sweep efficiency. The modeling work, as part of flood design process, is critical to the success of field implementations. The existing ASP models in finite difference simulators account for several mechanisms associated with the three chemicals but such complexity makes them computationally expensive for field-scale applications. This research focuses on developing a simplified one-dimensional flow model for ASP flood processes. We study and compare ASP modules in UTCHEM and ECLIPSE. UTCHEM is a compositional simulator that accounts for complicated mechanistic models and phase behavior while ECLIPSE is a black-oil simulator and uses a simpler model where relationships between parameters are described via input tables. We demonstrate that the existing capillary number dependent relative permeability model leads to discontinuity in simulation results in both simulators. We also show that increasing viscous forces has an equal impact as reduction in interfacial tension on miscibility, and hence it is possible to develop a partially miscible flood at zero surfactant. Our simulation results indicate that polymer, which is generally described as a mobility control agent and has no impact on microscopic displacement efficiency, can significantly reduce residual oil saturation under certain flood conditions. We define a simplified 1-D ASP transport model by accounting for water viscosity dependency on polymer concentration and interfacial tension reduction as a function of surfactant concentration. We successfully calibrate our simplified 1-D transport model with UTCHEM and ECLIPSE results. We use the 1-D model to explore an alternative of making miscibility resulting from the surfactant a direct function of surfactant concentration and thereby making relative permeability independent of the capillary number and avoiding the discontinuity observed in UTCHEM and ECLIPSE. We define a correlation for miscibility factor and surfactant concentration using a simple empirical function. We compare oil recovery obtained from the existing capillary dependent method with the proposed surfactant concentration method. Our studies highlight that the impact of capillary number dependency of the relative permeability model on oil recovery can be large or insignificant depending on where flood conditions lie on the capillary desaturation curve. We study the impact of surfactant on phase viscosity, and hence on the characteristics of fractional flow curves. To obtain a fractional flow curve that approaches a unit slope straight line as miscibility develops, not only relative permeability but also phase viscosity become a function of the miscibility factor. We applied a power mixing rule to modify continuously the water phase viscosity as miscibility develops so that the viscosity ratio becomes one and the linear fractional flow curve is achieved at fully miscible condition. We compare results of the power mixing rule case with the case where viscosity dependency on surfactant is neglected. The observation indicates that phase viscosity dependency on surfactant has significant impact on flow characteristics even with presence of polymer and that the proper modeling of phase viscosity is critical to chemical design and optimization.
Description
| Type of resource | text |
|---|---|
| Date created | June 2013 |
Creators/Contributors
| Author | Thirawarapan, Chanya |
|---|---|
| Primary advisor | Kovscek, Anthony R. |
| Advisor | Thiele, Marco R. |
| Degree granting institution | Stanford University, Department of Energy Resources Engineering |
Subjects
| Subject | School of Earth Energy & Environmental Sciences |
|---|---|
| Genre | Thesis |
Bibliographic information
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Preferred citation
- Preferred Citation
- Thirawarapan, Chanya. (2013). Simplified One-Dimensional Model for Alkali Surfactant Polymer Floods. Stanford Digital Repository. Available at: https://purl.stanford.edu/nh189kp7009
Collection
Master's Theses, Doerr School of Sustainability
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