ESPs Successfully Meet Challenges of CO2 Use in Tertiary Oil Recovery
Bibliographic record
Abstract
Technology Update Numerous operators are using CO2 injection as a means of significantly extending the oil life of a reservoir. Most oil fields initially produce without artificial lift (AL). Then as the reservoir pressure depletes some form of AL is employed. In many cases, secondary-recovery techniques, such as drilling horizontal producers or initiating water injection, are employed. Tertiary-recovery methods, which include thermal recovery and gas injection, can further expand recoverable reserves and extend field life. Each of these new tactics has presented learning curves for the operator and electrical submersible pump (ESP) provider. The CO2 learning curves are shrinking as the knowledge base grows. Success stories are growing as well. A major producer in Saskatchewan, Canada, has applied and refined miscible CO2 injection within a program of water-alternating-gas (WAG) injection that has added 155 million bbl of oil reserves and 25 years of life to the field. This operator has also implemented a program of CO2 sequestration. At the Rangely field in northwestern Colorado, CO2 injection has been incorporated into the WAG process. The injection program has added 114 million bbl of oil to recoverable reserves. Because of the high produced-fluid volumes resulting from enhanced-recovery methods involving water and gas injection, AL by means of electrical submersible pumps (ESPs) is often applied. ESP-System Challenges Posed By CO2 Injection Several potential problems affecting pump run life and performance can occur when an ESP is installed in a producing well where CO2 is present (Fig. 1). Carbonic acid attacks Asphaltene buildup Aromatic attacks on elastomers Gas impedance of pump performance Carbonate scaling Carbonic acid. The injected CO2 when mixed with water can form carbonic acid. This acid will attack the iron present in carbon-steel materials in the pump, tubing, and casing. If the fluid speed is low enough, the newly formed iron carbonate (siderite) will remain, creating a protective layer. The mechanical integrity of the component will not be degraded. If the fluid speed is great enough, the iron carbonate layer will be removed. This uncovers a new layer containing iron for the carbonic acid to attack. This mechanism will degrade the mechanical integrity of a carbon-steel component. CO2 corrosion exhibits itself uniquely from H2S, dissolved oxygen, chloride, or galvanic corrosion. Aggressive CO2 corrosion will create deep pits. These pits generally have sharp edges and rounded bottoms. As these pits deepen they will expose internal components to the well fluid. The corrosion pits commonly occur on the outside diameter of the housing material, but occasionally occur on the inside diameter of the pump housings (Fig. 2).
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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 | 0.004 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.004 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.006 | 0.003 |
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".