Optimal Voidage Replacement Ratio for Viscous and Heavy Oil Reservoirs
Abstract/Contents
- Abstract
- Historically a voidage replacement ratio (VRR) of 1 is assumed to be optimal for oil recovery regardless of whether recovery is occurring from an unconventional heavy oil reservoir or a conventional oil reservoir. That is, it is assumed that of all scenarios, the most oil recovery occurs when the amount of fluids injected into the subsurface equals the amount that comes out. Recently, work has been published that analyzed both field and core-scale data to conclude a VRR of 1 is suboptimal for certain kinds of viscous and heavy oil reservoirs. We seek to understand the conditions under which a VRR of 1 is suboptimal using simulation models. On core-scale models, we tested the sensitivity of the optimal VRR to the curvature of our relative permeability relationships, the critical gas saturation, the chemistry of our oil, the permeability distribution of our model, high and low permeability streaks, permeability cul-de-sacs, the reference scale at which we compare results, and our three-phase model. Realistic relative permeability curves based off rock and fluid interactions observed in the literature were developed and used in the majority of our simulations. We have found that gas mobility is an influential parameter in determining the optimal VRR. The heterogeneity in our model also influenced the optimal VRR to a lesser extent. Using a geological model of a deep-water, channelized reservoir, we observed at reservoir-scale the influence of heterogeneity and connectivity on the optimal VRR. We found connectivity plays a large role in influencing the optimal VRR on a reservoir-scale. Our results confirm earlier observations made using our core-scale models. Flow simulations using the reservoir model show that gas mobility and reservoir connectivity have the most influence over the optimal VRR. As the gas mobility decreases and/or the reservoir heterogeneity increases, a VRR below 1 becomes more favorable. Using realistic oil properties and relative permeability curves, we found cases where a VRR below 1 is optimal. In order to predict the optimal VRR using numerical simulation, one must properly characterize the relative permeability curves of the reservoir fluids and the connectivity of the reservoir
Description
| Type of resource | text |
|---|---|
| Date created | June 2012 |
Creators/Contributors
| Author | Delgado, David Emilio |
|---|---|
| Primary advisor | Kovscek, Anthony R. |
| 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
- Delgado, David Emilio. (2012). Optimal Voidage Replacement Ratio for Viscous and Heavy Oil Reservoirs. Stanford Digital Repository. Available at: https://purl.stanford.edu/tm677hy5042
Collection
Master's Theses, Doerr School of Sustainability
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