Abstract: A centralizer for tubular elements is provided which includes an inner part formed by a first material having high mechanical performance and chemical stability and an outer part arranged on said inner part, formed by a second material. The second material may be an autolubricating material. The second material may further possess a low coefficient of friction. The second material may additionally possess lower mechanical performance and chemical stability than the first material. A method of manufacturing the centralizer is also provided, including steps of injecting the first material on a tubular element to form the inner part on the tubular element and injecting the second material to form the outer part on the formed inner part.

Abstract: A centralizer for tubular elements is provided which includes an inner part formed by a first material having high mechanical performance and chemical stability and an outer part arranged on said inner part, formed by a second material. The second material may be an autolubricating material. The second material may further possess a low coefficient of friction. The second material may additionally possess lower mechanical performance and chemical stability than the first material. A method of manufacturing the centralizer is also provided, including steps of injecting the first material on a tubular element to form the inner part on the tubular element and injecting the second material to form the outer part on the formed inner part.

Abstract: An assembly of metal tube and radio-frequency identification (RFID) labels is provided. RFID labels are attached to the external surface of a tube and are placed at a distance less than 1 mm from the external surface.

Abstract: An elongated drive string assembly comprising a plurality of hollow sucker rods and a connecting elements with an axis, connected together and between a drive head located at the surface of an oil well and a rotary pump located deep down hole in an oil well. Each hollow sucker rod has at least a first end comprising an internal female threaded surface engaging an external male threaded surface on a connecting element, such as a nipple. In order to further optimize the stress distribution between the elements, frustro-conical, non-symmetrical threads with a differential diametral taper are used. Preferably two torque shoulders with a maximized mean diameter and cross-sectional area are used to resist storing reactive torque in the drive string. The nipple free end defines a second torque shoulder that adds to the torque transmission during make-up while also defining a small seal at that free end to decrease corrosion erosion problems.