| CPC E21B 17/042 (2013.01) [E21B 17/08 (2013.01); F16L 15/004 (2013.01)] | 20 Claims |

|
1. A tubular connection comprising:
a first joint of casing comprising an integral box end with an internal female threaded zone having internal female threads disposed on a box portion of the integral box end; and
a second joint of casing comprising a central longitudinal axis and an integral pin end with an external male threaded zone having external male threads disposed on a pin portion of the integral pin end, the external male threads configured to engage with the internal female threads such that the first joint of casing connects directly to the second joint of casing; and
a metal-to-metal sealing surface disposed between a lower most thread and a terminal end of the integral pin end;
wherein said second joint of casing has an internal diameter D1, said second joint of casing further comprising an internal annular recess having an internal diameter D2, wherein D2 is greater than D1, the internal annular recess disposed longitudinally along an inner surface of the second joint of casing, such that:
a virtual plane perpendicular to the central longitudinal axis intersects both the internal annular recess and the external male threads disposed on a lower portion of the integral pin end; and
the internal annular recess is not disposed longitudinally along an inner surface of the second joint of casing radially adjacent to the portion of the external male threads disposed on an upper portion of the integral pin end so as to maintain mechanical strength in the upper portion of the integral pin end on which the portion of the external male threads is disposed.
|