Fines Migration and Compaction in Diatomites and a Micromodel Investigation of Oil Sand Reservoirs
Abstract/Contents
- Abstract
- Unconventional resources have increasingly displaced conventional petroleum production through the development of thermal enhanced oil recovery schemes. This report studies two of these unconventional resources – the diatomaceous reservoirs of California and the oil sands of Alberta. The aim of these experiments is to investigate: - the effect of hot water flooding in diatomaceous cores with emphasis on the visualization, observation and modeling of fines migration, pH evolution and effluent ion concentrations, - the effect of compaction on the permeability of outcrop core data, and - the transportation of chemicals in the mobile water phase in oil sands micromodels. The effects of high temperature flooding in diatomaceous cores were studied through coreflooding at different temperatures several field and outcrop diatomite cores with simple NaCl brines of varying pH’s and salinities. The effect of temperature on fines migration was studied by the use of time-lapse CT scanning and the permeability reduction was modeled using the maximum retention function. Permeability reduction was seen at high temperatures for all tests confirming the importance of temperature in the elution of fines in reservoirs. It was found that the electric force from the DLVO theory governs the fines detachment and that the permeability reduction is more sensitive to salinity than pH. The point at which increased fines concentration is observed coincides with an increase in the range of oscillations in an averaged area in the CT images. Effluent brine analysis confirms that silica dissolution is an important factor in hot waterflooding with all of the tests indicating that silica dissolved in increasing quantities with increasing temperatures, even producing precipitates at 150-200 oC. This process leads to the general decrease in the effluent pH. Ionic exchange was also observed that is consistent with the Hofmeister series with cations of high valency and smaller hydrated radii displacing sodium. Boron was detected at high temperatures that may lead to incorrect values of the water saturation derived log values due to their neutron absorbing properties. The tests were not able to unambiguously determine the existence of gadolinium. The effect of confining pressure in the permeability of diatomaceous cores was investigated by repeated loading and unloading of outcrop cores at different intermediate pressures and at different temperatures. With increasing net effective stress, severe permeability degradation was observed with a noticeable acceleration at about 600 psia. Mercury porosimeter measurements indicate that this may be due to pore collapse. Almost no permeability recovery was detected when the core was unloaded. Significant creep was observed with significant permeability reduction resulting from a constant applied confining pressure. A slightly earlier permeability reduction was observed for the high temperature cases but no significant material differences in the primary compaction curves were detected between 25 oC and 100 oC for the outcrop diatomite samples tested in this study. Micromodels were filled with bitumen at different oil saturations and flooded with UV-dyed water and UV-dyed water containing 2% Neodol. This led to the visualization of water mobility inside partially saturated bitumen micromodels that were water-wet. Pore-filling effects, snap-off, and blob migration were the primary mechanisms of water movement. It was found that a mobile water phase is required in order to transport chemicals to the bitumen, leading to the production of normally immobile bitumen. This verifies the possibility of reservoir reconditioning when mobile water is present.
Description
| Type of resource | text |
|---|---|
| Date created | June 2013 |
Creators/Contributors
| Author | Lagasca, John Reuben |
|---|---|
| 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
- Lagasca, John Reuben. (2013). Fines Migration and Compaction in Diatomites and a Micromodel Investigation of Oil Sand Reservoirs. Stanford Digital Repository. Available at: https://purl.stanford.edu/nj305wd5416
Collection
Master's Theses, Doerr School of Sustainability
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