Application analysis of tubing with specially cham fer collar in Tarim Oilfield

Investigation on application of tubing in Tarim Oilfield indicates that the tubing with 90° shoulder collar may damage the rubber element of BOP during trips, and is often stuck at changes of casing string and in horizontal wells or highly-deviated wells. After investigation on the effectiveness of tubing with 18° specially and 20° specially chamfer collar, the author thinks that the use of these two types can avoid the above problems. Analytical calculation was conducted to the stress state of tubing with 18° or 20° specially chamfer collar during its use, and it was thought that the bearing surface of the 18° specially chamfer collar is more reasonable for bearing stress than that of the 20°. Hence, in order to reduce the types of tubing and ensure the service performance of tubing, the tubing with 18° specially chamfer collar should be used. This paper also makes suggestions as to how to transit from tubing with 90° shoulder collar and 20° specially chamfer collar to that with 18°.