Dual-Permeability Matrix–Fracture Corefloods for Studying Gas Flooding in Tight Oil Reservoirs
Bibliographic record
Abstract
Abstract Laboratory evaluation of tight oil production processes requires a unique coreflood apparatus that portrays both the tight rock matrix and fractures—a dual-permeability system. However, with some tight formations such as the Bakken having no available outcrop, full-sized actual cores are very difficult and sometimes impossible to obtain. In this study, a large-volume coreflood apparatus was developed to incorporate the detailed physics of ultra-tight, dual-porosity, dual-permeability flow in porous media. Also, large synthetic cores were made to represent the permeability, porosity, and mineralogy of actual tight reservoir rocks. To generate the desired dual-permeability system, fractures are simulated by creating sand-filled branched pathways in the large synthetic core. During a coreflood test, fluids are injected through the peripheral high-permeability belt into the tight matrix and recovered through the central fracture. This simulates the flow of matrix to fracture, or vice versa, seen in an ultra-tight reservoir. As well, either continuous gas/water injection or cyclic gas injection modes can be tested with the model. Two large-volume dual-permeability corefloods were conducted to study the effectiveness of immiscible field-produced gas flooding using recombined reservoir oil and synthetic tight cores. The corefloods simulated a practical field production sequence that included primary recovery (pressure depletion), injection of field-produced gas, pressurizing and soaking with this gas, and pressure depletion. The higher-recovery run produced 28.3% original oil in place (OOIP) including primary and tertiary (enhanced) processes. The dual-permeability corefloods demonstrated more representative performance of actual field operations than do traditional one-dimensional corefloods. The new matrix–fracture coreflood system better reflects the extreme permeability contrast between matrix and fractures that characterizes tight oil reservoirs. Therefore, history matching of its results using a numerical simulator is expected to provide much better representation in scaling up and predicting realistic field operations.
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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 | 0.000 | 0.000 |
| 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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".