Upscaling of Geomechanics in Heterogeneous Compacting Reservoirs
Bibliographic record
Abstract
Abstract Upscaling of properties for reservoir simulation has reached a stage of maturity and uses sophisticated techniques. In contrast, little work has been done on upscaling of mechanical properties for coupled modeling, and the geomechanical model is usually assumed to be representative (upscaled) without actually being subjected to the same rigor of process or scrutiny. Compacting reservoirs often contain fine sand-shale sequences on sub-grid scale (compared to flow modeling grid) and are typically represented in simulators by the net-to-gross (NTG) concept, while being ignored in geomechanical modeling. In this work, we present a method to upscale shales in the geomechanical component of a coupled simulation by computing dynamically changing equivalent moduli. The method is based on estimating the depletion of interbedded shales, coupled with analytical solutions for equivalent moduli under the assumption of uniaxial deformation. The technique has been verified by sub-grid scale simulations and requires geometric characterization of the shales but is relatively simple and can be easily implemented in coupled simulators. The analysis shows that the inclusion of the shales generally reduces computed compaction, with the controlling variables being NTG, dimensionless pressure depletion of the shales (which in turn depends on their flow properties) and mechanical properties of the shales. The approach developed was incorporated in the subsidence and compaction analysis over a complex offshore oil reservoir. The reservoir zone consisted of a number of intervals that included relatively undeformed as well as highly deformed layers, and on reservoir model scale had significant NTG ratios. A comprehensive study (based on coupled flow and geomechanics simulation) was conducted to evaluate well integrity, fault slip (reactivation) and compaction drive. A large full field model was built using data from a multitude of sources and production data was modeled and history matched, allowing us to estimate the magnitude of reservoir subsidence and the contribution of the NTG effect on predictions. The study presented here showed that in the absence of any consideration of the NTG effect, predictions (for compaction and subsidence) could be significantly overestimated. In addition, the method can be used to study the phenomena of "time-lag" of subsidence which has been observed in some 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".