Analysis of stuck pipe in deviated boreholes
| Autor: | Kenneth Larsen, Bernt S. Aadnøy, Per Cato Berg |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Drill stem test
Buoyancy business.industry Directional drilling Borehole Torsion (mechanics) Drilling Analytical equations Drill pipe Structural engineering engineering.material Geotechnical Engineering and Engineering Geology Drill string Physics::Fluid Dynamics Fuel Technology Drag engineering Differential sticking Torque Geotechnical engineering business |
| Zdroj: | Journal of Petroleum Science and Engineering. 37:195-212 |
| ISSN: | 0920-4105 |
| DOI: | 10.1016/s0920-4105(02)00353-4 |
| Popis: | The complexity of the wells haveincreased significantly inlater years. Reach has more than doubled, and highinclination and fully 3-D well paths are common. However, statistics shows that sidetracking the boreholes due to stuckpipe has also shown a significant increase, and is presently ahigh cost factor. The margins between success and failure arenow much smaller. A larger study was initiated to understand the stuck pipesituation better, and to develop improved procedures. Amechanistic approach was chosen. The following elementswere analyzed: 1) the forces developed during differentialsticking, 2) pipe strength under combined loads; tension, torque and pressure, 3) effects of buoyancy under variousconditions like equal or different mud densities in drillpipeand annulus, 4) wellbore friction as related to torque and drag. This paper presents new equations to determine depth to thestuck point in deviated wellbores, based on pulling tests andtorsion tests. In particular it is shown that bends in thewellbore leads to more friction, which with the new equationsresults in a deeper stuck point in a deviated well compared to asimilar vertical well. Knowing all the forces involved in astuck pipe case, another analysis was performed to determinethe action that has largest impact to free the pipe. One of themain conclusions is that the most important element to freethe string is to keep the bottomhole pressure as low aspossible. The paper will present three methods to free thepipe, which where developed from the analysis: 1) maximummechanical force method, 2) minimum density method, and 3)maximum buoyancy method. A detailed field case from theYme field in the North Sea will demonstrate these methods, and show the effect on the stuck point using each method. In addition to the field case, the paper will in the Appendicespresent the complete equations for pipe stress and strengthunder 3-dimensional loading, and define the effects ofbuoyancy in deviated wellbores. In particular is the buoyancyissue resolved, showing the differences and similaritiesbetween "the piston force approach" and the law ofArchimedes, as applied to deviated wellbores. |
| Databáze: | OpenAIRE |
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