Torsional Strength And Sealability Simulation Analysis Of Casing Threaded Connection In Casing Drilling

Casing drilling is a revolutionary breakthrough in the technical field of drilling, it cansimplify the traditional drilling technology, reduce the drilling accidents and cut down drillingcost markedly, it is causing widespread concern in domestic and international petroleumengineering. It puts forward higher requirements on the torsion and sealing property ofthreaded connection in the development and application of the casing drilling technology, butthe API casing threaded connection can’t meet the requirements of torque transmission andsealing, so, it has a very important engineering significance to development a special threadedconnection for casing drilling.Firstly, we analysed the structure, working environment, loads of casing drilling string,contrasted the theoretical calculation and finite element simulation methods of make-uptorque.Based on a large number of the casing drilling literature researching, ascertained the wellconditions and parameters of the casing in casing drilling. We took the Ф177.8mm×9.19mmcasings that commonly used in casing drilling as the objects of study, built the2-Daxisymmetric finite element models of threaded connections by using ANSYS, by comparingthe torsional properties and tensile properties of API LTC and BTC, we provided sometheoretical bases for selecting the button type of casing thread connection which speciallyused in casing drilling.We designed the torque shoulder structure of thread connection which specially used incasing drilling, by comparing the torsional properties of thread connections with differentshoulder gaps, we put forward some suggestions for devising the torsion structure of casingthread connection.Based on summarizing the sealing mechanisms of API and non-API casing thread connections, we compared the sealing properties of cone-to-cone and column-to-sphereleakproof structures, then provided some references for the design and selection of sealingstructure of casing thread connection.We attempted to do3-D simulation analysis of casing thread connection by using theANSYS Workbench and Pro/E.At the end of the paper, we summarized the buckle type, the torsional and seal structuresof thread connection which suitably used in casing drilling, provided some solutions forselecting and designing of thread connection.