Best Practices in DFIT Interpretation - Comparative Analysis of 80 DFITs in the Canadian Montney Shale Play
Bibliographic record
Abstract
Abstract Current practice for conducting minifrac or diagnostic fracture injection tests has been changing with time. The Alberta Energy Regulator (AER) has a pressure and deliverability testing directive that has guidance on those tests. This guidance was updated in late 2021. Many operators from the Canadian Montney shale play submit minifracs to AER, 80 of these minifracs were summarized statistically in this paper. Closure, reservoir pressure, and permeability were the main analyzed parameters in the paper scope. Requirements for pressure and deliverability tests are set out by this newly updated directive. Industry uses minifrac in horizontal wells with multistage fracture treatments when developing unconventional reservoirs. Closure, initial reservoir pressure is commonly being determined with the common well test. Holistic or tangent vs. compliance method are compared for closure pressure in this paper. Readers are eager to replicate results, so for After Closure Analysis (ACA) methods equations that govern the analysis are provided in detail. Published or commercially available holistic and compliance models are compared for closure pressure. Published or commercially available ACA Soliman and Nolte methods are compared for permeability and reservoir pressure. Horizontal wells in 80 unconventional shale field case studies are presented. The fact that the signature of closure pressure is not apparent is a significant finding. Similarity of closure pressure outcomes or estimates for tangent vs compliance is remarkable. Differentiation of reservoir pressure determination for either linear or radial flow are observed. Interpretation on net pressure impact is evaluated and ultimately differentiation on ACA permeability determination is assessed. Analogous shale plays operators in USA and current Canadian Montney Shale play operators will find practical and direct implications. To calculate effective fracture half length and optimize fracture design and well spacing accurate permeability values are needed. To design hydraulic fractures with geomechanics applications accurate closure pressure values are essential. To conduct Rate Transient Analysis (RTA) for resources and reserves assessment in similar unconventional shale plays accurate initial reservoir pressure as an input is fundamental. Comparing analytically closure pressure methods in unconventional shale plays is novel. In addition, practicing engineers or well testing interpreters will find the comparison of different after closure analysis relevant.
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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 | 0.013 | 0.036 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.010 | 0.011 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.005 | 0.001 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".