Study On The Relationship Between The Parameters Of Tubing Round Thread And The Stress And Strain Of Screw Root

Tubing is one of the most important tubular goods in oil and gas industry. But accidents of tubing failure occurred frequently due to the hostile environments and the complex loading conditions the tubing serviced in. Statistics in and abroad showed that the main failure forms of tubing were galling, corrosion, pierce, decollement and fatigue fracture, which not only shortend the service life of tubing but also increase the cost of workover operations, and most importantly, the productivity of wells was affected and made huge economic losses.Statistics showed that tubing failure occurred mainly at the root position of the first tooth of the thread connection. The nature of tubing failure was the damage of tubing thread. The quality of the thread connection directly affected the life of tubing. The quality of the thread connection depended on geometry parameters of it, which should be studied deeply.Therefore, the mechanical model of thread connection was established based on mechanics of materials and plasto elasticity. The stress and strain of the2-7/8" J55non-upset tubing round thread was simulated under different geometry parameters by finite element analysis. And the relationship between geometry parameters and stress-strain was analyzed to determined the effect order of geometry parameters. Research results can provide theoretical references for companies to optimize thread parameters, effectively improve the stress distribution and make further enhancement on the quality of thread. A standard was established for tubing judgement, which provided reference for oil field to determine tubing abandonment.