Predicting Accelerating Subsidence Above the Highly Compacting Luconia Carbonate Reservoirs, Offshore Sarawak Malaysia
Bibliographic record
Abstract
Summary Sarawak Shell Berhad has a number of offshore gas fields that produce from the Luconia carbonate formation, which can exhibit high-compressibility pore-collapse deformation. Recent accelerated subsidence has been observed at several of these fields, which extrapolates to final subsidence values well above previous estimates. This paper describes a geomechanical study involving core work to determine if the Luconia formation compressibility is sensitive to brine flow from the rising aquifer and a 3D geome-chanical finite-element model developed to predict future subsidence and lateral movements for the F23 platform. Compaction tests were performed on the Luconia core from three different gas fields. Tests on twin plugs were conducted—one plug undergoing a standard uniaxial zero-lateral-strain compaction test, while its twin has several pore volumes of simulated-formation brine flowed through it (at virgin in-situ stress conditions) before the compaction loading. Four sets of compaction tests on twin plugs were completed. The higher-porosity samples showed characteristic pore-collapse behavior consistent with previous measurements on Luconia mouldic limestone core. No sensitivity to brine flow was observed. In-situ compaction logs in the field also do not show increased compressibility in sections flooded by the rising gas-water contact (GWC). The geomechanical model uses a relatively simple structural model comprised of four layers—two overburden formations, the Luconia carbonate and one underburden formation. A nonlinear deformation model for the Luconia formation captures the accelerating pore-collapse response observed in the core and in-situ compaction measurements. The model is calibrated to GPS-measured platform subsidence and is consistent with measured core- and field-compaction properties. The results predict that platform subsidence rates with depletion would level off, with a maximum subsidence of 18.5 ft +/− 1 ft at an abandonment pressure of 300 psi. Platform subsidence in the two years following the work continues to follow the predicted values. This work illustrates the importance of integrated geomecha-nical core testing, field-monitoring measurements, and modeling to accurately predict compaction and subsidence effects in highly compacting environments.
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 | 0.003 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".