Study On Sealing Performance Of Casing Thread With Metal Seal Principle

As the typical application products of metal seal technology, casing connections are commonly used during drilling and production operations in the oil industry. The performance of sealing obviously depends on structure parameters, and the tolerance of thread could also affect performance by changing status of metal-to-metal contact. Selecting two kinds of premium connections with sealing structure of cone/cone type and cylindrical/spherical type as the research objects, this paper analyzes the influence of thread parameters and structure parameters on contact pressure of sealing structure and shoulder in different condition.FEA results indicate that:(1) the contact pressure of shoulder is more sensitive to the tolerance of lead and taper, the tolerance of pitch taper and diameter highly affect the contact pressure of sealing surface. On account of the tolerance, shoulder contact pressure of cone/cone sealing structure has better performance in the makeup condition than cylindrical/spherical type, whose contact pressure of sealing structure is more stable.(2)The contact pressure of shoulder is sensitive to the structure parameters, also, while a contrary trend is observed in primary sealing structure. The premium connection with sealing structure of cone/cone type is applicable under the condition of make-up. On the other hand, the cylindrical/spherical type structure is suitable under tensile.(3)The contact pressure of sealing structure of cylindrical/spherical type is higher than cone/cone type. Moreover, sealing structure parameters hardly affect contact pressure, which means the sealability of cylindrical/spherical type is stable and reliable. As for cone/cone type structure, sealing performance is hardly affected by thread parameters, which can significantly reduce the possibility of sealing failure cause by thread deformation.