Mitigation of Reservoir Souring by Nitrate in a Produced Water Re-Injection System in Alberta
Why this work is in the frame
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Bibliographic record
Abstract
Abstract We report the reduction in levels of H2S in produced gas and water using nitrate treatment in an oilfield in Southern Alberta that is under produced water re-injection. Approximately 4,500 m3/day of water is injected, primarily produced water supplemented with make-up water from the outfall of a municipal waste treatment plant. The reservoir is 30-40°C. Calcium nitrate was continuously applied at 150 ppm (as nitrate) into the injection water at a central water plant and distributed to injection wells field wide. A biocide, acrolein, was also applied in weekly batches to treat the injection lines and prevent nitrate-fed biofilm accumulation. After one month of treatment, H2S in the produced gas from one gathering system dropped from an average of 170 ppmv to 110 ppmv (average 3.4 kg/day to 1.8 kg/day). This represents an approximately 50% reduction in produced H2S in the gas. A corresponding decrease in H2S in the produced water was observed. One problematic well maintained an H2S level of approximately 800 ppmv. To treat this well, a nearby injector was started on a weekly treatment of a single batch of calcium nitrate dosed to approximate 600 ppm, based on a seven-day production rate. Sulfide levels in the problem well dropped significantly and over the subsequent 18 months there has been on average <15 ppmv H2S in the produced gas.
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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 it