Multidisciplinary insights into the origin of natural gas from hydrocarbon generation and charging history of Permian dolomite reservoir in Sichuan Basin
Why this work is in the frame
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Bibliographic record
Abstract
Understanding the origin of natural gas in deep and ultra-deep reservoirs with multiple potential source rocks remains challenging due to the complex thermal evolution of hydrocarbons at high temperatures and multi-stage accumulation processes. This study investigates the origin of natural gas in deep hydrothermal dolomite reservoirs of the Maokou Formation, eastern Sichuan Basin , using hydrocarbon inclusion analysis, radiometric U-Pb dating of calcite cements, maturity modeling of potential source rocks, and constraints on reactivation periods of the nearby No. 15 Fault System. Results indicate an oil charging event at approximately 246.9 Ma, followed by two episodes of gas charging at 222.4 Ma and 175.2 Ma. Furthermore, the oil and gas charging events occurred synchronously with activities of the No. 15 Fault System, suggesting that its reactivation induced episodic hydrocarbon migration . Maturity modeling indicates that during the oil charging period, source rocks in the Qiongzhusi, Wufeng-Longmaxi, and first member of the Maokou formations reached the stages of dry gas generation, significant oil generation, and the threshold of oil generation, respectively. During the subsequent two-episode gas charging periods, the Qiongzhusi and Wufeng-Longmaxi formations progressed to dry and wet gas generation stages, respectively, while the first member of the Maokou Formation attained the oil generation stage. The hydrocarbon charging time and maturity history of potential source rocks indicate that: 1) oil in hydrothermal dolomite reservoirs predominantly originated from the Wufeng-Longmaxi Formation at approximately 246.9 Ma; 2) during the subsequent gas charging episodes, the Wufeng-Longmaxi Formation could contribute wet gas, while the Qiongzhusi Formation likely supplied cracking gas from kerogen and residual liquid hydrocarbon; 3) all oil in the hydrothermal dolomite reservoirs underwent thermal cracking to gas at approximately 110 Ma. This study indicates that gas pools in (ultra-)deep carbonate reservoirs of the Sichuan Basin have mixed genetic origins, with contributions from multiple sources. The multidisciplinary approach, combining direct dating of hydrocarbon charge events and simulation of hydrocarbon generation , proves robust and effective in identifying the origin of natural gas in (ultra-)deep reservoirs.
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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 | 0.001 | 0.001 |
| 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