Numerical Modeling of Cuttings Transport With Foam in Vertical Wells
Bibliographic record
Abstract
Abstract In this study, a 1-D unsteady-state two-phase mechanistic model of cuttings transport with foam in vertical wells has been developed. The model is solved numerically to predict the optimum foam flow rate and rheological properties to maximize the cuttings transport efficiency in vertical wells. The numerical solution allows analyzing the effects of borehole geometry, drilling rate, foam rheological properties, gas and liquid flowing rates and reservoir fluid influx on the cuttings transport efficiency when drilling vertical wells. Results of sensitivity analysis study are presented. Comparisons of model predictions with the field test data have shown that model predictions are in close agreement with the field test results. A discussion of the deficiencies of an existing foam drilling models is also provided. Introduction The Alberta Energy and Utilities Board defines underbalanced drilling (UBD) as "when the hydrostatic head of a drilling fluid is intentionally designed to be lower than the pressure of the formation being drilled, the operation will be considered underbalanced drilling"1. The benefits of UBD include increased productivity by reducing formation damage, increased rate of drilling bit penetration, minimization or elimination of lost circulation, improved formation evaluation while drilling, reduction or elimination of differential pipe sticking, reduced stimulation requirements, and earlier production. Four drilling methods are referred to as UBD:air drilling: air, nitrogen and some hydrocarbon gases can be used as circulating medium;flow drilling: fluid with density below the formation's hydrostatic gradient is used as circulating fluid;gas/liquid drilling: A gas-liquid two-phase drilling fluid is used in the drilling operation;foam drilling: stable foams are used as cuttings transport media. Because of its variable density and good cuttings transport ability, foam is favorably used in UBD operations. Applications of foam as a drilling fluid in many drilling operations and the results from various field cases were well documented in the literature 2–15. Field application of the foamed drilling fluids is very often complicated because of the difficulties encountered in controlling their hydraulic properties. In general, comparing to conventional (incompressible) drilling fluids, much less is known about the hydraulic and rheological properties of foamed drilling fluids, and even less is known about their cuttings transport capabilities. The complex flow mechanism involving in compressible drilling fluid circulation makes determination of the optimum combination of liquid and gas injection rates very difficult. Other questions also exist, such as how to predict the bottom-hole pressure and how to combine different controllable variables in order to obtain optimum cuttings transport performance and bit hydraulics. In order to simulate the hydraulics of the foam drilling realistically, factors including foam rheological properties, drag coefficient of cuttings in foam, formation fluid influx, drillpipe eccentricity, and drilling rate, need to be considered in any modeling study. An example of such a modeling study is presented in this article. Literature Review Following sections provide a review of literature on cuttings transport in general, rheology of foam and cuttings transport with foam.
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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".