Petrophysical Characterization of Bioturbated Sandstone Reservoir Facies In the Upper Jurassic Ula Formation, Norwegian North Sea, Europe
Bibliographic record
Abstract
Abstract: A petrophysical study of bioturbated shoreface sandstone rocks was completed by mapping local variations in air permeability measured in core samples acquired from the Upper Jurassic Ula Formation of the Norwegian Central Graben. Analysis of the shoreface fabrics resulting from bioturbation was studied using arithmetic, harmonic, and geometric numerical modeling and analytical techniques. The arithmetic mean best illustrates samples dominated by high volumes of horizontal or subvertical burrows (50–80%). The distal Skolithos to proximal Cruziana ichnofacies is an example of a rock fabric that can be characterized using the arithmetic mean. The harmonic mean best exemplifies samples dominated by low volumes of vertically oriented burrows (10–50%). The archetypal Skolithos ichnofacies is an example of a rock fabric that can be characterized using the harmonic mean. At extreme volumes of bioturbation (90–100%), isotropic flow units begin developing irrespective of burrow orientation. Numerical models of Ophiomorpha in two different sedimentary bedding features (laminated sandstone and massive sandstone) show that single-phase fluid flow is influenced by parameters such as burrow permeability, burrow connectivity, and bioturbation volume. Spot-permeametry measurements show that the Ophiomorpha burrows have higher permeability values than the host matrix. In the laminated-sandstone models, horizontal shale laminae and low bioturbation intensities promote lamination-parallel fluid flow. At higher volumes of bioturbation, fluid flow becomes increasingly isotropic due to greater amounts of burrow interpenetrations across mud laminae. In the massive-sandstone model, no flow barriers exist. As such, low volumes of bioturbation result in only minor influences on fluid flow. At higher volumes of bioturbation, greater burrow interconnectivity occurs and results in an enhancement of vertical and horizontal burrow permeabilities. Based on the results outlined above, this paper emphasizes the impact bioturbation plays in helping improve reservoir quality in the Ula Formation. Perhaps more importantly, the effectiveness of the numerical models presented to characterize fluid flow in different bioturbated fabrics (e.g., archetypal Skolithos ichnofacies) highlights the fact that the fluid-flow results outlined in this paper can also be applied more broadly to different shoreface successions using ichnofacies knowledge alone.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 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 | 0.001 |
| 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".