Bibliographic record
Abstract
Abstract A number of wells in western Canada have been drilled into lower pressure, lost circulation reservoirs, which has increased the use of foamed and lightweight cements. This paper compares the properties of foamed and lightweight cements and makes recommendations regarding the most appropriate situations in which each should be used. Specific emphasis is placed on the equivalent circulating density (ECD) variation between foamed and lightweight cement which demonstrates the high ECD's experienced when pumping foamed cement. A cost comparison between lightweight and foamed cements was also completed and demonstrated a 39% reduction in costs when lightweight cement was utilized. Finally, a case history in which 54 wells were switched from foamed to lightweight cement is presented along with the associated success rate and cost savings. Introduction The Western Canadian Sedimentary Basin contains a large number of low pressure and lost circulation reservoirs. As a result, there has been a strong growth in the use of lightweight and foamed cement systems. Foamed cement was introduced into the Canadian oil industry in the early 1980's. Foamed cement operations were originally plagued by operational inconsistencies which have caused the technique to fall in and out of favour over the years. In the last 10 years, however, operational, design and slurry improvements have allowed the jobs to be placed with a higher level of quality and the technique has been used to combat lost circulation and zonal isolation problems in some fields throughout western Canada. Lightweight cement has been in existence for more than 40 years. The original lightweight cements used extenders and water absorbing additives to control free water while lightening the slurry. The next generation used low density solids such as Gilsonite and ceramic spheres to reduce density and absorb water. The third generation of lightweight cements was introduced in the early 1990's and consisted primarily of adding silica fume to the slurry which had the ability to tie up large amounts of water and still maintain strength. As a result of the handling problems, health hazards, and quality control issues associated with silica fume, however, a new generation of lightweight cements has been introduced in recent years. These cements use combinations of slag, silica, zeolites, specialty cements, ceramic spheres and other chemicals to lighten slurries to densities as low as 1200 kg/m3. All foamed and lightweight cements experience similar problems of reducing density and hydrostatic pressure while still maintaining adequate compressive strengths to meet local regulatory guidelines. In Alberta, the Alberta Energy and Utilities Board requires that cement across a hydrocarbon zone achieve a minimum of 3500 kPa compressive strength in 48 hours. Meeting this requirement has resulted in innovative technology to achieve strength requirements in wells with shallow hydrocarbon zones that are near surface and may have only a 25 °C bottom hole temperature. Both foamed and lightweight cements exhibit properties which make them valuable for combating different zonal isolation issues. This paper defines the properties of each system and discusses situations where each should be applied.
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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".