Unlocking the Value in West Sak Heavy Oil
Bibliographic record
Abstract
Abstract West Sak is a heavy oil accumulation within the Kuparuk River Unit on the North Slope of Alaska. It is a Cretaceous, shallow marine sandstone. It contains 7–9 billion barrels of oil in place with an oil gravity that ranges from 10–22 degrees API. Initial oil production began in 1997 at approximately 3,000 BOPD and has increased to over 16,000 BOPD in March 2005. Development plans are in place to achieve a rate of over 40,000 BOPD by 2007. This paper describes the evolving development plan for the West Sak field, with emphasis on the technical advances that have resulted in large-scale commercial development. Early West Sak development consisted of stimulated vertical wells on a 40-acre waterflood pattern with typical production rates of 150-250 BOPD. Utilizing the evolution in horizontal and multi-lateral drilling technology, the development plan has progressed to extended reach multi-lateral injectors and producers with horizontal and undulating slotted liner completions is excess of 8000 feet per lateral. Peak rates of over 5000 BOPD and sustained rates of over 1500 BOPD have been achieved. With the higher reservoir throughput rates, the distance between wells has increased, reducing well count and improving the development cost per barrel. Significant changes have also been made to the completion design and production strategy. These include changing from sand exclusion to sand management, adding intervention capabilities with multi-lateral completion equipment, optimizing the drill-in-fluid, and adding a backup gas lift system to the standard electrical submersible pump (ESP) completions. Finally, the enhanced recovery process has evolved from waterflood to a viscosity reducing water-alternating-gas (VRWAG) process, improving expected recovery by 2-3 percent of OOIP. Application of new technology and optimized development decisions have reduced development cost by approximately 25% in terms of $/BOE and unlocked value in a major resource.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.003 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
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".