Stratigraphy, Stable Isotopes, and Hydrocarbon Potential of the Aptian Shuaiba Formation, U.A.E.
Bibliographic record
Abstract
Abstract The Shuaiba Formation of the United Arab Emirates (U.A.E.), forms one of the most important petroleum reservoirs in the Arabian Gulf. Its reservoir quality is controlled by diagenetic processes that were active during early shallow burial to late deep burial. Detailed well log evaluation, petrographic and geochemical studies of carbonate diagenesis, X-ray diffraction, cathodoluminescence microscopy, and oxygen and carbon isotopic determinations from cores and an outcrop section allowed evaluation of the stratigraphic and depositional framework of the Shuaiba Formation, its diagenetic history, and the prediction of its local reservoir potential. The Shuaiba Formation consists of two informal and one formal members: the lower Shuaiba and upper Shuaiba members and the Bab Member, in ascending order. The Shuaiba ranges in thickness from 45 to 145 m, having accumulated in a wide range of depositional settings from shallow to deep shelf. The lithofacies identified within the Shuaiba Formation include peloidal skeletal algal packstone/grainstone; ooidal-peloidal grainstone/packstone; skeletal algal (Lithocodioidea) floatstone; intraclastic and coated packstone/grainstone and skeletal wackestone/ packstone. These facies were deposited during third-order depositional sequences, including two transgression system tracts (TST) separated by a highstand system tracts (HST). Diagenetic alteration of the original carbonate components proceeded through marine, shallow burial, and deeper burial settings related to stabilization of the carbonate matrix, cements, and rudist shells. Oxygen and carbon isotopes of calcific matrix have the least altered components of these rocks (av. δ180 = 5.7%o PDB; δ13C = +2.5 %o PDB), whereas the calcite cements occluding shell porosity and veins have more depleted isotopic values (av. δ180 = 8.8%o PDB;δ13C = +0.5%o PDB). The variations of oxygen and carbon isotopes reflect changes in the water-rock interactions and increasing burial. The carbonates of the lower and upper Shuaiba members have porosities between 12% and 32% and permeabilities between 1.0 and 160.0 md. The reservoir quality is highly affected by the diagenetic processes which include stabilization of metastable carbonate phases, cementation, dolomitization, stylolitization, and dissolution. The Bab Member, which was deposited in a basinal setting, is organically rich and forms substantial source rock in the eastern and northeastern parts of central UAE and is mature enough in deep troughs to generate and expel hydrocarbons to the 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 | 0.000 | 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) | 0.001 | 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".