Hydraulic-fracturing induced seismicity in Alberta, Canada: Analysis and interpretation using dense local arrays
Bibliographic record
Abstract
Unconventional oil and gas development is associated with anthropogenic earthquake activity worldwide. In particular, hydraulic fracturing, which involves the injection of high-pressure fluids into the subsurface, has been observed to trigger induced seismicity in some areas. The Duvernay Formation in Alberta is a target of hydraulic fracturing and has experienced induced earthquakes up to magnitude 4.2. To study hydraulic fracturing-induced seismicity in greater detail, a local dense array of sensors was used to collect four weeks of passive seismic data over a 4-well pad. In this thesis, this dataset is processed and interpreted using a variety of techniques. Supplementary information, such as waveform data from broadband seismometers and an accelerometer that were co-located with the dense geophone array, is also used to aid the interpretation. In some cases, it is found that the magnitude-frequency distribution obtained from the monitored seismicity deviates from the expected power-law form associated with the Gutenberg-Richter relationship. In particular, the largest earthquakes, greater than Mw 3.0, are larger than statistically expected given the observed seismicity. Spectral analysis of a subset of events reveals complex source spectra. For example, some of the events show evidence of a double corner frequency and a source time function with multiple peaks. A detailed analysis of the timing of events relative to the hydraulic fracturing stages reveals that natural fracture networks within the Ireton Shale, overlying the target Duvernay Formation, provided permeable conduits for an expanding region of elevated pore pressure. Using simple diffusive modelling, it is shown that these fracture networks allowed pore pressure to perturb fault systems at distances of over 1 km, consistent with observations of fault activation during treatment. In two datasets that are used in this thesis, shear-wave splitting analysis of microseismic waveforms provides evidence for stress rotation near the largest faults. Integration of these investigations provides a basis for a new working model for induced seismicity in the Fox Creek, Alberta, area.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".