To prevent fracture of a box under a tensile load without increasing the outer diameter of the box. The presently disclosed threaded joint for pipes includes a pin provided with a male thread portion at one end of a first pipe, and a box provided with a female thread portion at one end of a second pipe, where each of a plurality of thread grooves of the female thread portion has a corner portion on a load flank side and a corner portion on a stabbing flank side on a thread bottom side, a corner portion on a load flank side of a first thread groove includes a first arc portion that has a first curvature radius, and a second arc portion that has a second curvature radius, and a ratio of the second curvature radius to the first curvature radius is 3 or more.

A coupled pipe connection system may include a coupling with internal threads adapted for joining two pipe sections by threaded engagement of external pipe threads with the internal coupling threads. A torque ring may be disposed within the coupling and between the first pipe and the second pipe. The torque ring may an outer cylindrical surface, at least a portion of which may include a plurality of tapered threads engaged with and tapered to match a mid-length axial section/J-space of the inner threads of the coupling. Annular faces of the torque ring may be beveled inwardly or outwardly and adapted for mating engagement with corresponding beveled annular faces of the pipe ends. Torque rings of gradually decreasing axial lengths may be incrementally swapped out as the number of make-up cycles increases. Couplings having internal shoulders of gradually decreasing axial lengths may be used instead of torque rings.

A threaded connection for steel pipe is provided that can be made up quickly and appropriately. The threaded connection includes a steel pipe 20m, a steel pipe 20f, and a coupling 50 for connecting the steel pipes 20m and 20f. The pipe bodies 21m and 21f of the steel pipes 20m and 20f include annular marking grooves 23m and 23f, respectively, formed on the outer peripheries of the pipe bodies 21m and 21f.

A directly connected drill pipe applicable to extreme conditions includes a tool joint pin and a tool joint box, where an external pipe section is located on an external side of a threaded section of the tool joint pin, and an annular groove is formed between the external pipe section and the threaded section of the tool joint pin. An insertion section of the tool joint box can be inserted into the annular groove in a matched manner. A main shoulder of the tool joint pin is located at an end of the external pipe section, a main auxiliary shoulder of the tool joint pin is located on a bottom surface of the annular groove, and an auxiliary shoulder of the tool joint pin is located at a small end of the tool joint pin. The tool joint box has three corresponding shoulders which form a 3-stage sealing with the tool joint pin.

A system includes a box end disposed on a first tubular. The box end includes a first shoulder, a sealing surface, a first distal portion, and first threads disposed between the sealing surface and the first distal portion. The system further includes a pin end on a second tubular. The pin end includes a second shoulder, a second distal portion comprising an extended lip, and second threads disposed between the second shoulder and the extended lip. A first swellable element is disposed around the extended lip and the pin end is inserted into the box end to form the expandable connection. Upon expansion of the expandable connection, the first swellable element seals against the sealing surface. Upon separation of the expandable connection, the extended lip of the pin end acts as a floating seal assembly with the box end acting as a receptacle for the floating seal assembly.

A screw joint in which an efficient screw length of a joint portion is achieved. This screw joint is for an oil well pipe of an integral type and includes: (i) a pin that is provided with a male screw portion which is a male taper screw, at one end of a steel pipe; and (ii) a box that is provided with a female screw portion which is a female taper screw fitted to the male screw portion, at one end of the steel pipe, in which a structure, in which the pin and the box are in metal contact with each other to seal a fluid, is provided at least at one place of a seal portion on an outer peripheral surface side of a pipe end side of the pin and a seal portion on an inner peripheral surface side of a pipe end side of the box.

A tubular threaded joint for drilling, operating hydrocarbon wells, or transporting oil and gas includes a male tubular threaded element and a female tubular threaded element. The female tubular threaded element includes a female internal threaded portion and a female non-threaded portion. The male tubular threaded element includes a male external threaded portion and a male non-threaded portion. At least the male or female tubular element includes a body and a portion added by additive manufacturing that includes at least one first abutment surface.

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 flush joint high torque thread that achieves superior tensile efficiency and compression efficiency. In one example, the thread of a pin member and a box member includes a thread a chamfer with angled shoulders on each side of the thread to achieve increased torque. The stab flanks each contain a lead-in chamfer extending no further than a thread pitch line. The load flanks are each tapered. The stab flanks engage each other during assembly, but not upon assembly. The load flanks do not engage each other during assembly, and do engage each other upon assembly. The pipe achieves both a 70% tensile efficiency and a 90% compression efficiency.

A modified API buttress threaded casing connection is disclosed for use in drilling oil and gas wells in lieu of using conventional drill pipe. The coupling threads only are modified to include a reduced thread height thread form to relieve thread stresses at axial ends of the coupling. The reduced thread height thread form may be mated with standard single tapered API buttress thread forms formed on the pin ends. The axial length of the coupling may be generally shortened to permit abutment of the mating pins at the center of the coupling.