Understanding lateral and vertical fluid variations in the Pliocene sandstone reservoirs in the eastern South Caspian Basin
Bibliographic record
Abstract
ABSTRACT The South Caspian Basin hosts more than 600 onshore and offshore oil and gas fields characterized by large variations in fluid properties impacting field development and nearby exploration efforts. A total of 32 surface and downhole fluid samples collected from six distinct Pliocene sandstones in an offshore anticline field in the eastern South Caspian Basin were analyzed (gas, light- and midrange–fraction composition, biomarkers, and bulk and gas compound-specific carbon isotopes) to investigate the processes controlling the fluid properties at the field scale. Sampling and sample handling methodologies enabled preservation and recovery of representative light-end compositions. Lateral fluid property variations within the main productive sandstone reservoir (API gravity from 36.8° to 53.4° and gas–oil ratio from 544 to 947 SCF/bbl) were found to result from the combined effects of biodegradation, water washing, and a light charge contribution, the latter having the predominant impact on the observed fluid properties variations. Ongoing migration of higher-maturity fluids generated deeper in the South Caspian Basin or evaporative fractionation, which likely affected fluids in the deeper sandstones, may be responsible for the contribution of a volatile enriched charge to the shallow reservoirs. A comparison based on source and maturity diagnostic parameters with Pliocene reservoir oils from the western South Caspian Basin is consistent with a similar reservoir filling history but more complex migration pathways for the eastern South Caspian Basin reservoirs.
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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 | 0.000 |
| 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 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".