Impact of Solvent Loss During Solvent Injection Processes
Bibliographic record
Abstract
Abstract Only 5 - 15% of the oil in Lloydminster heavy oil reservoirs is recovered during cold heavy production with sand (CHOPS). Solvent injection processes are being explored as a means of recovering the heavy oil remaining in the reservoir after CHOPS has been completed. Solvent retention becomes a main concern for the process economics. This paper evaluates the relative importance of different solvent retention mechanisms and how solvent can be recovered from the reservoir so that solvent injection processes (e.g. cyclic solvent injection (CSI), Vapor Extraction Process (VAPEX), thermal solvent, and steam-solvent) can be economically viable. In particular, CSI is a promising post-CHOPS follow-up process. Sources of solvent loss / retention include: Solvent trapped in the reservoir due to surface and interfacial forces including adsorption and capillary pressureSolvent vapor (free gas or trapped bubbles) in porous mediaDissolution in un-recovered oilDissolution in formation water or thief water zonesOther possible sources such as:Lack of confinement of injected fluids; especially important for post-CHOPS reservoirsHydrate formationPrecipitated asphaltenes Three experiments were performed to estimate solvent losses due to different retention mechanisms. In these experiments, gaseous propane was injected into a sand pack to a pressure of 750 kPag and then depressurized (at an ambient temperature of 21 °C) in 100 kPa steps to 50 kPag. The propane produced at each depressurization step was measured. The sand packs used in the experiments were: Sand pack initially saturated with water ("wet pack")Dry sand packSand pack initially flooded with water and then with dead Husky Edam oil The experimental results showed that there was significant propane retention in unproduced oil and as solvent gas. However, little propane adsorption occurred on the sand as it had a small surface area due to an insignificant amount of clays being present in the test packs. Solvent adsorption in a reservoir can be significant if there is a considerable amount of clays with a large surface area. It may be particularly high when shale is present. Propane concentrations in the produced water from the wet pack were similar to literature values. Solvent loss in water was small due to the low pressures involved in the test. However, solvent loss in water will be significant if the solvent dissolves into the formation water at high temperature (for liquid solvent) and/or high pressure especially if there is a significant water source to sweep away the dissolved solvent or the water causes hydrate formation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".