Lateral Buckling—The Key to Lockup
| Autor: | Tore Weltzin, Robert F. Mitchell |
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| Rok vydání: | 2011 |
| Předmět: | |
| Zdroj: | SPE Drilling & Completion. 26:436-452 |
| ISSN: | 1930-0204 1064-6671 |
| DOI: | 10.2118/139824-pa |
| Popis: | Summary Conventional wisdom suggests that buckled pipe first forms a plane buckled configuration, then transitions to a helical shape as the axial load increases. The helical configuration has been studied extensively using analytic solutions that allow calculation and analysis. Lateral buckling has received much less attention because no analytic solution exists for smooth pipe. Most conclusions about lateral buckling are just guesses. Tool joints have received some analysis, and buckling calculations, both lateral and helical, have been made for pipe with connectors, but these calculations have received little attention from the industry. Buckling tests (Weltzin et al. 2009) were performed in the Ullrigg U2, a 2020-m research well with a buildup and 60° tangent geometry. These tests represent a major advance in the understanding of drillstring buckling. Although there have been many laboratory-scale studies and a few full-scale tests of limited value, this study is the first full-scale study to acquire a large amount of high-quality buckling-displacement data for analysis. This paper presents the calculated drillstring positions for two loading tests performed in build and inclined sections of the Ullrigg U2 test well. Both tests were loaded until drillstring lockup. By lockup, we mean that no increase in load could be transmitted to the load sensor at the bottom of the drillstring with further decreases in hookload at the surface. In both cases, lateral buckling was the primary buckling mode, with only a short interval in the build-section tests showing actual helical buckling. The results from the Ullrigg U2 tests show that connectors appeared to have primary importance in the buckling behavior of drillpipe, and lateral buckling was the primary mode of behavior. These results, which were not expected, will require considerable revision of the conventional buckling models with much more focus on the impact of connectors and a deeper understanding of lateral buckling. In particular, the analysis of casing running in extended-reach horizontal wells will be impacted significantly. |
| Databáze: | OpenAIRE |
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