Critical Elements Extraction from Flowback and Produced Water: From Lab to Field
Bibliographic record
Abstract
Abstract Flowback and produced water (FPW) from multi-fractured horizontal wells (MFHWs) are possible sources of critical elements (CE) from unconventional hydrocarbon reservoirs. The objective of this study is to compare temporal variations of CE (Li, Mg) concentrations in FPW at lab- and field-scales, with examples from prominent Canadian unconventional hydrocarbon plays. A secondary objective was to evaluate whether CE could be extracted (i.e. ‘leached’) from reservoir rocks by FPW. Quantifying elemental leaching is important for reserves evaluation and identifying the relative importance of mechanisms contributing to CE enrichment in FPW (e.g., fluid mixing vs. fluid-rock interaction). High-temperature (150 °C), high-pressure (2200 psi) fluid-rock interaction experiments were conducted on three crushed-rock Montney (siltstones/sandstones) and Duvernay (organic/clay-rich shales) samples with variable composition, fabric, and reservoir quality. Time-lapsed fluid analysis (+30 days), using spectroscopy and ion chromatography (ICP-OES/IC) enabled observations of Li and Mg concentration profiles at the lab-scale. Lab-scale Li and Mg concentration profiles were then compared to post-fracture Li and Mg concentration profiles from multiple MFHWs completed in the Montney and Duvernay formations (public data). At the lab-scale, maximum measured Li concentrations for the Montney and Duvernay samples were 0.27 mg/L and 0.53 mg/L, respectively. Maximum lab-scale Li recoveries were significantly (about two orders of magnitude) smaller than those measured in the field (28-72 mg/L for the Montney wells, 26-54 mg/L for the Duvernay wells). This could be attributed to the 1) dominance of the fluid mixing mechanism in the field, relative to fluid-rock interaction, 2) variable rock-water mass ratios at lab and field scales, and/or limited (initial) content of Li in the analyzed samples, amongst other factors. Lab-scale Li and Mg concentration profiles exhibited similarities to and discrepancies with those observed in the field. Notably, larger Li concentrations (up to twice) were associated with lower pH, in agreement with field observations. Interestingly, lab-scale Li and Sr concentrations appear to co-vary for the Duvernay FPW, in agreement with field observations, suggesting the possibility of using Sr as a ‘proxy element’ for predicting Li anomalies in the Duvernay FPW. Quantifying temporal evolution of CE concentrations in FPW is essential for evaluating the feasibility of CE recovery from MFHWs and the selection of optimal Li extraction technologies over the well lifetime. This study provides the first-time comparison between lab- and field-scale temporal variations of CE concentrations in FPW for the purpose of evaluating CE extraction from unconventional hydrocarbon reservoirs.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".