Patent ID: 6056073
Filing Date: 2000-05-02
Classification: E21B

Abstract:
An element of a drill pipe string which is rotatable in a forward direction,said drill pipe string element comprising at least one tubular portion (2a, 17a, 17'a, 17b, 17'b, 27, 27') having a generally circular transverse cross-section, a longitudinal axis, and an external surface containing at least one groove (8, 8a, 8b, 8c, 8d, 8e, 18a, 18'a) arranged in a helix having as an axis the longitudinal axis (7, 19) of the portion,wherein the groove (8, 8a, 18'a) has a cross-section which, in a plane perpendicular to the longitudinal axis (7, 19) of the portion (2a, 17a, 17'a, 17b, 17'b, 27, 27'), has an undercut part (10, 20) lying to the rear, with respect to said forward direction, of a radius (OA) of the generally circular cross-section of the portion (2a, 17a, 17'a, 17b, 17'b, 27, 27'), said radius passing through an external end (A) of the area of the groove lying to the rear of the groove with respect to the forward direction of rotation (.OMEGA.) of the pipe string, andwherein the groove (8, 18a, 18'a) is bounded to the rear of the groove by an approximately straight line (9b) making a rearward undercut angle (.beta.) with the radius (OA) of the generally circular cross-section of the portion.