The casing is made of connecting single oil well pipe with thread. The screw connection part of the string is the weak key link. The general standard of thread is API standard. In API standard, the thread form is round thread or offset ladder thread. There are some problems in ensuring the structural integrity and sealing integrity of the string. With the development of petroleum industry, especially the development of deep well, ultra deep well, high-pressure gas well and directional well, higher requirements are put forward for the use performance of petroleum casing. The casing with API standard thread connection is difficult to meet the production demand in many cases. In addition to meeting the joint performance, premium connection also needs to have good sealing performance under extreme environment and composite load.

The double sealing surface premium connection introduced in this paper is a ball to cone metal seal with double sealing surface. The structure is made into a double sealing surface by changing the angles of two adjacent sealing surfaces at the shoulder of the coupling.

The double sealing surface premium connection includes a pipe body and a coupling. The pipe body is a male end with a male thread, the coupling is provided with a female thread, and the male thread and the female thread are matched to form a threaded connection. Male end is successively provided with male outer sealing surface, male thread with taper, male inner sealing surface and male shoulder at the vertex of male inner sealing surface. The coupling is successively provided with a female outer sealing surface, a female thread with taper, a female inner sealing surface and a female shoulder behind the female inner sealing surface. The threaded connection forms the main sealing surface after matching, the auxiliary sealing surface after matching and the shoulder after matching.