Lab Investigation of EOR Potential for a Stack Pilot
Bibliographic record
Abstract
Abstract Laboratory studies of unconventional reservoirs are faced with considerably more challenges than those of conventional reservoirs. The assessment of Enhanced Oil Recovery potential in unconventional reservoirs (UCR EOR) in particular needs to address the characterization of static and dynamic properties given the tightness of the rocks, available sample size and simulation of EOR under elevated pressure and temperature conditions. This paper summarizes a laboratory study designed and performed for a potential EOR pilot utilizing cyclic gas injection (Huff-n-Puff) in the Sooner Trend Anadarko Canadian Kingfisher (STACK) shale play in Oklahoma. The lab study focuses on characterizing the rock-fluid interactions as well as upscaling key parameters for the field-scale modeling and simulation. A systematic approach was followed in the design of a laboratory program specific to the characteristics of rock/fluid interaction and the proposed injection scheme of a cyclic gas injection pilot. Digital Core Analysis (DCA) incorporating micro CT, SEM and FIB-SEM analyses were performed in order to determine basic petrophysical properties at micro scale, with capillary pressure and relative permeability curves simulated digitally. Porosity and relative permeability end points were also measured on preserved STACK core plugs. Minimum miscibility pressure (MMP) measurements of field separator gas and STACK crude oil was performed with a rising bubble apparatus (RBA). Finally, a huff-n-puff experiment was designed and performed within a custom pressure cell to study the recovery efficiency at the existing core sample scale. Digital Core Analysis (DCA) has been shown to reliably produce petrophysical properties for tight STACK cores. Laboratory miscibility pressure measurements were conducted at reservoir conditions (4,500 psi and 183 °F) using field crude samples and the associated gas composition. Seven injection/production cycles were applied to a re-saturated standard core plug with oil production observed and measured in the effluent. Cyclic injection continued until no further oil could be visually observed in the effluent. A customized 2-stage drawdown was incorporated to provide input for the recovery process. The total recovery after seven cycles reached 82 %OOIP. This work provides the first rock and fluid analysis integrating digital and traditional approaches for assessment of EOR potential in unconventional reservoirs such as those found in the STACK. This systematic approach presents properly designed and executed laboratory experiments without leaving out key formation and fluid variables. This workflow can be applied in similar UCR EOR studies to lay a solid foundation for appraising UCR EOR potential and providing reliable inputs for upscaling to the field level studies.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".