caa a22 4500 606226052 CHVBK 20210128101151.0 cr unu---uuuuu 210128e20150701xx s 000 0 eng 10.1007/s10553-015-0604-y doi (NATIONALLICENCE)springer-10.1007/s10553-015-0604-y Analysis of the Critical Buckling Loads and Contact Loads on Coiled Tubing String in a Vertical Microhole [Elektronische Daten] [Hou Xuejun, He Jia, Sun Tenfei] Microhole technology is a novel technology for wellbore diameters less than 88.9 mm and uses coiled tubing (CT) as the tubing string for downhole operations. The CT cannot rotate in the downhole due to the small diameter of the microhole, so that a sliding force is needed to trip the CT into the microhole. As a result, high friction is generated between the CT and the wellbore. Problems such as buckling and even lock-up occur under compressive loads, which severely impairs downhole operations of the CT in the microhole. In this work, a detailed analysis is made of CT operating conditions in a small-diameter vertical wellbore. The critical buckling loads and associated contact loads on CT strings of different diameters are calculated using well-developed models, and a study is made of the dependence of the critical buckling loads and corresponding contact loads on various parameters. The results show that the critical buckling load increases with CT diameter and that coil pitch width increases with CT diameter and a decrease in the annular clearance between the CT and the wellbore wall. The contact load between the CT and the wellbore wall increases with an increase in the axial compressive load and decreases with an increase in CT diameter. To reduce friction and contact loads and to trip the CT smoothly into vertical microholes, a larger-diameter CT and a smaller compressive load should be used while maintaining adequate annular clearance. Springer Science+Business Media New York, 2015 microhole nationallicence vertical well nationallicence coiled tubing nationallicence sinusoidal buckling nationallicence helical buckling nationallicence critical load nationallicence contact load nationallicence Xuejun Hou Chongqing University of Science and Technology, Chongqing, China aut Jia He Harold Vance Department of Petroleum Engineering, Texas A&M University, College Station, Texas, USA aut Tenfei Sun CNOOC Research Institute, Beijing, China aut Chemistry and Technology of Fuels and Oils Springer US; http://www.springer-ny.com 51/3(2015-07-01), 308-319 0009-3092 51:3<308 2015 51 10553 https://doi.org/10.1007/s10553-015-0604-y text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10553-015-0604-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Xuejun Hou Chongqing University of Science and Technology, Chongqing, China aut NATIONALLICENCE 700 1- Jia He Harold Vance Department of Petroleum Engineering, Texas A&M University, College Station, Texas, USA aut NATIONALLICENCE 700 1- Tenfei Sun CNOOC Research Institute, Beijing, China aut NATIONALLICENCE 773 0- Chemistry and Technology of Fuels and Oils Springer US; http://www.springer-ny.com 51/3(2015-07-01), 308-319 0009-3092 51:3<308 2015 51 10553