Depositional conditions and accumulation models of tight oils in the middle Permian Lucaogou Formation in Junggar Basin, northwestern China: New insights from geochemical analysis
Bibliographic record
Abstract
ABSTRACT Recent discoveries of huge tight oil resources in the middle Permian Lucaogou Formation within the Jimusaer sag in the Junggar Basin in northwestern China have aroused numerous studies on this unconventional petroleum system. However, depositional conditions of the source rocks and the accumulation models of the oils are still unclear because of the complexity of the petroleum system. In view of this, systematic geochemical investigations on 120 samples covering a whole variety of source and reservoir rocks in the Lucaogou Formation were carried out. Based on the results, two types of depositional conditions were identified for the five sections of source rocks (denoted A–E), with sections A, C, and D deposited under hypersaline and reducing conditions, and sections B and E under brackish and relatively oxidizing conditions. Oil-source rock correlation results demonstrated that four groups of oils (denoted 1–4) with distinctive geochemical signatures from the formation finally accumulated in three relatively independent subsystems (labeled Sub-I to Sub-III). Groups 2–4 oils (Sub-II and Sub-III) originated solely from interbedded mudstone, so the accumulation model is highly interbedded and nearby accumulation. Group 1 oils (Sub-I) are originated from the vertical mixing of hydrocarbons produced by multiple mudstone beds at greater depths followed by lateral migration, thus called vertical-lateral mixing accumulation model. This study highlights the importance of lateral migration in tight oil accumulation and will benefit future tight oil exploration in the Junggar Basin, such as the Permian Feng Cheng Formation, and other areas worldwide.
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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 | 0.001 |
| 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 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".