A threaded connection for large diameter steel pipe exhibits high torque resistance and high sealability and, at the same time, provides a shear resistance that suits the size of the steel pipe to be connected. The threaded connection includes a tubular pin provided on a tip of a steel pipe with large diameter, and a tubular box 20 adapted to be drawn up on the pin as the pin is screwed in. The pin includes a male threadform made with a taper thread. The box includes a female threadform made with a taper thread. Each of the threadforms are wedge threads and have a dovetail-shaped cross section. The male threadform is designed such that the width of the thread in an end region of the male threadform closer to the tip is set to a size corresponding to the size of the pipe body of the steel pipe.

There is proposed a thread connection for casings used for construction of vertical, directional and horizontal wells. The connection includes male and female elements, whose ends, both externally and internally, are produced correspondingly with tapered trapezoidal threads, sealing, transition and shoulder end surfaces. Crests and roots of the thread turn profile are parallel to the axial line of thread. Additional surfaces are formed as a taper surface on the female element and a taper surface or convex spherical surface on the male element. Transition from the sealing surfaces to additional surfaces are formed as concave spherical surface on the male element and of convex spherical surface on the female element. High tightness of the connection under sufficient mechanical loads is achieved by improving characteristics of the connection make-up, prevention of jamming of the connection at the initial stage of make-up, lack of damages (galling) of sealing surfaces.

A tubular member includes a tube body, a tube end, an exterior surface, an interior surface, a nominal wall thickness, a longitudinal axis, a welded seam, and a patch of material. The welded seam forms an arcuate portion of the interior surface, and the patch covers a portion of the interior surface that includes a portion of the welded seam, extending from the tube end to an axially spaced first location. The resulting interior surface from the tube end to the axially spaced first location has a uniform inside diameter.

A tubular member includes a tube body, a tube end, an exterior surface, an interior surface, a nominal wall thickness, a longitudinal axis, a welded seam, and a patch of material. The welded seam forms an arcuate portion of the interior surface, and the patch covers a portion of the interior surface that includes a portion of the welded seam, extending from the tube end to an axially spaced first location. The resulting interior surface from the tube end to the axially spaced first location has a uniform inside diameter.

A pin member of threaded connection includes a body and a male thread positioned on the body. The male thread includes a male thread principal portion, a male thread transition portion with a cross-sectional area that is smaller than a cross-sectional area of the male thread principal portion, and a male thread protrusion with a cross-sectional area that is larger than the cross-sectional area of the male thread transition portion with the male thread transition portion positioned between the male thread principal portion and the male thread protrusion.

A pin member of threaded connection includes a body and a male thread positioned on the body. The male thread includes a male thread principal portion, a male thread transition portion with a cross-sectional area that is smaller than a cross-sectional area of the male thread principal portion, and a male thread protrusion with a cross-sectional area that is larger than the cross-sectional area of the male thread transition portion with the male thread transition portion positioned between the male thread principal portion and the male thread protrusion.

A threaded connection for steel pipe that provides high torque performance, high tension performance and high sealability is provided. A threaded connection 1 includes: a tubular pin 10 including a pin shoulder 12, a male thread 11 and a pin seal 13; and a tubular box 20 including a box shoulder 22, a female thread 21 and a box seal 23. The male and female threads 11 and 21 are constituted by wedge threads. The pin seal 13 is provided between the pin shoulder 12 and the male thread 11. The box seal 23 corresponds to the pin seal 13 and is located on the inner peripheral surface of the box 20. When the connection is made up, the pin shoulder 12 is spaced apart from the box shoulder 22. The threaded connection 1 satisfies the following expression, (1):

3%≤(LP−SP)/LP≤7%   (1).

In expression (1), LP is the pitch between loading flanks 111 of the male thread 11, and SP is the pitch between stabbing flanks 112 of the male thread 11.

A threaded connection for steel pipe that provides high torque performance, high tension performance and high sealability is provided. A threaded connection 1 includes: a tubular pin 10 including a pin shoulder 12, a male thread 11 and a pin seal 13; and a tubular box 20 including a box shoulder 22, a female thread 21 and a box seal 23. The male and female threads 11 and 21 are constituted by wedge threads. The pin seal 13 is provided between the pin shoulder 12 and the male thread 11. The box seal 23 corresponds to the pin seal 13 and is located on the inner peripheral surface of the box 20. When the connection is made up, the pin shoulder 12 is spaced apart from the box shoulder 22. The threaded connection 1 satisfies the following expression, (1):

3%≤(LP−SP)/LP≤7%   (1).

In expression (1), LP is the pitch between loading flanks 111 of the male thread 11, and SP is the pitch between stabbing flanks 112 of the male thread 11.

An elongate component, such as a drill rod or adaptor, forms part of a drill string having a shoulder contact male spigot coupling. The male spigot includes a non-threaded shank and a threaded section in which an axial length of the non-threaded shank is provided at a predetermined minimum relative to an outside diameter of the spigot at the threaded section.

An elongate component, such as a drill rod or adaptor, forms part of a drill string having a shoulder contact male spigot coupling. The male spigot includes a non-threaded shank and a threaded section in which an axial length of the non-threaded shank is provided at a predetermined minimum relative to an outside diameter of the spigot at the threaded section.