Safety Analysis Of The Tubing In Directional Well Based On The Buckling Theory

The tubing in directional well is the informational and material channel in the oilexploration and exploition. According to statistics, duirng the process of drilling, testing andcompletion, the buckling deformation of the tubing and strength failure of the buckling tubingare the pirmary cause for the tubing accident. So the safety analysis of the tubing in directionalwell based on the buckling theory had been studied in this paper.First of all, the formula of the critical load of the buckling tubing with initial bending wasdeirved using the energy and transfer matirx method. And the impact of the well tract, radicalclearance and tubing size on the buckling cirtical load of the tubing were studied. Based on theconclusion, the condition of the tubing in the directional well could be decided. According tostatistics, the chief cause why the tubing in directional well could be destroyed is the strengthfailure of the tubing, and usually the value of the4th equivalent stress is considered as thestandard to judge whether the strength failure would be happened. So the analysis method of thestrength of the spirng was used to derive the4th equivalent stress formula of the helicalbuckling tubing. Then the impact of the axial press, radical clearance and tubing seize on the4thequivalent stress of the helical buckling tubing were studied, and then the safety of the tubing indirectional well could be predicted. Because the packer would influence the boundary conditionof the tubing and impact the stress distribution, the safety of the tubing nearby the packer mustbe analysed especially. At last, according to the transformation law of the buckling critical loadand equivalent stress of the tubing, the combination suggestions of the tubing were proposed.And the safety analysis of the tubing in directional well could be guided by the conclusion.