Investigation of Effect of Equivalent Diameter Definitions on Determination of Pressure Losses of Non-Newtonian Fluids in Annuli
Bibliographic record
Abstract
Abstract Accurate estimation of pressure losses associated with fluid flow in annuli is essential to achieve better bottom hole pressure control in drilling operations. Control of formation pressures and optimization of hydraulic programs can be obtained only if the pressure losses in the circulation system are precisely known. One of the major challenges in determining actual annular pressure losses is that the non-Newtonian fluid flow in annular conduit is much more complex than pipe flow. Many investigators proposed different equivalent diameter concepts to link annular flow to well defined pipe flow. In this study, effect of using various equivalent diameter definitions together with three widely used rheological models is analyzed for different annular conditions. The study is aimed to show how pressure losses vary as rheological model and equivalent diameter definitions are coupled. The effects of the ration between inner and outer radius and the effect of flow rate on the accuracy of equivalent diameters are shown in the study as well. It is important to note that, based on the complexity of wellbore configuration, different equivalent diameter definitions might result in more accurate calculations for different parts of the system. This study provides guidelines to predict frictional losses with higher accuracy. Introduction While drilling fluid is circulated in the annulus, it exerts additional pressure on the wellbore. If frictional pressure losses in the annulus are not determined accurately, the equivalent circulating density (ECD) calculations will also be incorrect increasing the chances of having well control problems. Determination of pressure losses in annulus is harder due to the complexity of the geometry compared to regular circular geometry present in pipe flow. Depending on the clearance between wellbore (or casing inner diameter) and pipe outer diameter, and also on the flow rate required to carry cuttings effectively, flow might be in turbulent or laminar regime. Several authors analyzed the non- Newtonian flow in annular conduits and suggested either empirical or analytical solutions. However, disagreement between calculated and measured pressure losses, due to the complex nature of non-Newtonian fluids, still exists today. Fredrickson and Bird1 have derived an analytical expression to determine frictional pressure losses in annulus for Power Law rheological model. Their approach gives reasonable results when inner to outer radii ratios are more than 0.5. Kozicki, Chou and Tiu2 determined a relation between maximum velocity and pressure loss for Power Law fluids flowing in ducts of arbitrary cross-sections under laminar flow conditions. Zamora and Lord3 proposed a new numerical and graphical technique to determine pressure losses of non-Newtonian fluids in pipes and annuli. The model is valid for Bingham Plastic, Power Law and Yield Power Law rheological models. Langlinais, Bourgoyne and Holden4 compared actual annular pressure losses obtained from two wells with theoretical calculations. They found out that pressure losses are more sensitive to the definition of annular gap compared to rheological model.
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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 | 0.005 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".