1. Field of the Invention (Technical Field)
The present invention relates to joints in continuous pipes and pipe-like structures, particularly oil and gas drill and production pipes and to a method of connecting drill pipe.
2. Background Art
Present drill pipes depend on connectors to join manageable lengths of pipe together to form a drill string. Because of the stresses, the joints must be reinforced by using thick section or saddles. These connectors are inherently heavier than the pipe they join. In most cases, such as A.P.I., the full section is wastefully continued in the total pipe length.
A thinner wall pipe could be used if the connection was continuous. Welding of the tube with conventional methods is lower in strength than the parent metal and the time to weld is too long to weld the length during oil production (typical).
Present methods and systems of forming joints in continuous pipes and pipe like structures, particularly oil and gas drill and production pipes typically involve either machined joints or welded joints. Referring to the machined joints, typically they include the following components: a) Threads, b) Swaging, c) Wedging, d) Sliding, and e) Seal joints, whereas the welded joints involve the following components: a) Scarf welded, b) Welded and machined, c) Weld and field beat treatment.
The mechanical machined joints require costly machined pipe ends and fittings. Mechanical joints require assembly of several components and are limited by a MIX of materials (rubber/plastics and close tolerance parts). The result is a high cost penalty and a maintenance component for the life of the system, particularly where collars and rings have differing galvanic couples. For example, aluminum pipes with steel saddles corrode rapidly in sea water, causing the aluminum to fail.
The present welded pipes, although often semi-automatic, have metallurgical limitations because the scarfed ends must be welded using filler metal. This system requires large molten areas of metal causing loss of control of metallurgical chemistry and loss of control of grain growth and texture. The weld zone does not match the parent metal strength and integrity. The weld zone is generally larger than the pipe profile, requiring remachining or producing handling problems if disregarded. The weld zone also causes a variation in corrosion rates, causing loss of strength at or near the joint through stress corrosion or metal loss.
All the present systems have a severe limitation in that the pipe a) is not uniform in strength, b) is not uniform in sectional size, and c) cannot be processed to provide continuous laying or continuous drilling operations.
The new invention provides unprecedented levels of metallurgical integrity and parameter control in field operations, using standard mill products with no pre-machining costs. This invention solves all the present systems' problems and in particular overcomes the limitations expressed above of the prior technology, with particular reference to the following applications: a) Rotating drill pipe (oil fields land/seabed), b) Fluid transfer pipe: Horizontal production pipe oil/gas/water, "J" lay vertically deployed to seabed, c) Piles/pylons, d) Masts, e) Storage tanks land/sea, f) Flexible pipe: angle drilling oil/gas/water, contour land/seabed.
Accordingly, it is desirable to provide for a new and improved welded/machined drill pipe with no connectors and a method of providing a continuous pipe employing electronic beam welding for constructing continuous pipe to an undersea well extending undersea, by the application of its inherent parts.