Geochemical characteristics and geological significance of produced water from coalbed methane wells in Junlian, Sichuan
Bibliographic record
Abstract
The geochemical characterization of coalbed methane (CBM) well drainage water contains rich information on the source of formation water, which can reflect the conditions of CBM preservation, and is of great significance to the study of CBM enrichment mechanisms and exploration and development. Taking 19 typical CBM wells in 9 groups of the Junlian block at the southern margin of the Sichuan Basin as the research objects, experimental tests of conventional ions, trace elements, hydrogen and oxygen isotopes of produced water were carried out, and the source of produced water in CBM wells was discussed in combination with the variation law of produced water conventional ions with drainage time. The results show that the Na++K+ ratio in the produced water of coalbed methane wells in Junlian block is more than 90%, and the TDS is 1203～143099 mg/L, the Cl− is 709～85700 mg/L, the \begin{document}${\mathrm{SO}}_4^{2-} $\end{document} is 12～3614 mg/L, and the \begin{document}${\mathrm{HCO}}_3^- $\end{document} is 24～4516 mg/L, which is unique characteristics of “high TDS, high Cl−, high \begin{document}${\mathrm{SO}}_4^{2-} $\end{document}, and low \begin{document}${\mathrm{HCO}}_3^- $\end{document}”. During the ten-year discharge period, Cl− showed a fluctuating decrease; \begin{document}${\mathrm{SO}}_4^{2-} $\end{document} was more stable at about 20-25 mEq/L in the early stage and began to fluctuate around 1500 d; and \begin{document}${\mathrm{HCO}}_3^- $\end{document} was the lowest. There are mainly three types of produced water in Junlian CBM wells: primary sedimentary water of marine origin, infiltrated water recharged by atmospheric precipitation, and mixed water, and the change of produced water shows a mixing process from infiltration of atmospheric precipitation to primary sedimentary water in both time and space scales. With the infiltration of atmospheric precipitation, the water type of produced water changes from Ca/Mg-Cl type to Na-SO4 type and then to Na-HCO3 type; the content of trace elements decreases gradually, among which Sr and B elements are more sensitive to the source of the produced water; the hydroxide isotope value of the produced water decreases gradually, and the hydroxide isotope fitting line is gradually close to the meteoric water line. Various geochemical indicators show that well G1-2, which is located in the axial part of the broad and gentle syncline, are better closed and produce mainly marine sedimentary water, while well G3, which is located in the flank part of the anticline, is poorly closed and the source is mainly atmospheric precipitation, and the rest of the wells are in between, which are a mixture of paleo-seawater and atmospheric precipitation.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 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".