Analysis of the Taper Thread Stand-off Influence Tightness of the Sleeve Structure on the Axial Preload

The Measurement While Drilling (MWD) tool comprises various instruments with different functions connected in series. The instruments with different functions are connected by taper thread. The taper thread is also basically used in the internal structure design of each instrument. With high connection strength and good sealing performance, China Oilfield Services Limited Trapezoidal Thread Two (CT2) taper thread can realize an overall angle change rate. To meet the functional requirements of the sleeve structure, an independent CT2 taper thread was designed. The difference between the theoretical and calculated stand-off was then compared. Based on strict theoretical reduction on make-up torque and axial preloading, we obtained the axial preload value of the instrument. Analysis of the taper thread sleeve structure on the axial preload value of the instrument compared the difference value between theoretical stand-off difference and calculated difference. Divide the thread make-up process into three stages for force analysis, the basic concept of over-twisting and under-twisting applies to the three-stage force analysis, to obtain design methods and considerations. The comparison of measurements allowed for the calculation of the difference, which arises from the axial deformation of parts under tensile and compressive forces within the sleeve structure. This was achieved by resolving the effects of long stand-off on axial preload and the resulting changes in the stress state.