Experience of a Reservoir Waterflood Failure and Remediation Treatment in the Stag Reservoir, Australia
Bibliographic record
Abstract
Abstract The Stag field operated by Apache Energy Limited is located on the North-West Shelf Australia. Waterflooding is used to maximise production rates and reserves recovery. An unusual failure of the reservoir occurred in late October 2000, between a subsea horizontal injector and a platform based horizontal producer, 2130 ft apart. In effect, a reservoir short-circuit was created between the wells. This reservoir failure circumvented the waterflood and had the potential to isolate reserves between the two wells. Analysis of the failure data indicates the short-circuit was caused by high stresses in the weak reservoir formation. The failure appears to be a wormhole like failure. A tracer study was implemented to provide information on the short circuit dimensions and to design a remedial treatment. The tracer took 2 hours 50 minutes to travel between wells indicating direct communication and a volume of the short circuit flow path in the order of 150-190 bbls. Lack of isolation options through the uncemented pre-perforated liners would make any re-mediation difficult and expensive. This provided motivation to first attempt remediation by a comparatively inexpensive polymer treatment injected through the subsea injector and into the short-circuit. Following the polymer treatment, a cement squeeze through the producer was performed to block the short circuit. This paper reviews the unusual reservoir failure, the tracer study, polymer treatment and subsequent cement shut-off. Included is detail on treatment designs, implementation utilising existing platform equipment and interpretations of the results. This paper is a helpful case study to those designing and implementing water shut offs, identifying waterflood problems and testing low cost re-mediation alternatives. The paper raises an alternative failure mode that could be experienced in waterflood operations in weakly consolidated reservoir rock.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".