Abstract: Apparatus for compressing a fluid comprising a tubular, open-ended housing (2) having a suction end (5) and a discharge end (6), a tubular, open-ended rotor (8) rotatably arranged in the housing (2), an annular driver space (17) which is defined between the inner surface of the housing (2) and the outer surface of the rotor (8), an annular seal preventing fluid flow from the annular driver space (17) to the suction end (5), a rotor driver (20) arranged in the annular driver space (17), and a rotor-driven compressor (30) arranged in the tubular rotor (8), wherein the rotor-driven compressor (30) includes a helical screw blade (32) which is secured to the inner surface of the tubular rotor (8), and wherein the pitch of the helical screw blade (32) decreases in the direction of the discharge end (6).

Abstract: A liner at the bottom of an oil or gas well is perforated and the surrounding formation is subsequently fractured by inserting into the liner a perforating and fracturing apparatus comprising a pair of packers that can be positioned around fragile spots of the liner, and subsequently injecting a fluid or fluids at an elevated pressure into the area between the packers in order to perforate the liner at the locations of the fragile spots and to create fractures in the formation surrounding these spots.

Abstract: This invention relates to a method and device for joining well tubulars by a friction welding technique. The device includes apparatus for fixing tubular elements in a substantially vertical and aligned position near the wellhead and apparatus for rotating a welding ring relative to the tubular elements. According to the method a first tubular element is lowered partly into the well, positioning a welding ring positioned on top of this element hoisted to a substantially vertical position above the welding ring and the welding ring rotated relative to the tubular elements while the welding ring is deformed in a radial direction such that sufficient frictional heat is generated to create a friction weld between the welding ring and the tubular elements.

Abstract: A sealing joint for use in a conduit system where an elevated pressure may exist at one side of the system comprises a pair of co-axial tubular metal sections with intermesting tapered edges which are clamped against each other by fastening means, such as a swivel nut, so as to establish a fluid tight seal formed by the conical contact area between the tapered surfaces of said edges.One of the tubular sections has a tapered edge which is at one side thereof exposed to the elevated pressure. This section has a smaller wall thickness than the tapered edge of the other tubular section so as to allow the elevated pressure to press said tapered edges onto each other.