Blast joint for snubbing installation

A method for attaching a blast joint to installed production tubing and inserting the blast joint into a well through snubber unit, comprising the steps of:

• assembling a first length of a blast joint having a first length of production tube, a concentric sub attached to a lower end of the production tube, a first set of erosion-resistant rings stacked vertically on the outside of the production tube, and a first length of pressure jacket extending vertically outside the erosion-resistant rings;
• attaching the first length of blast joint to a lifting means which independently supports the first length of production tube, the first length of pressure jacket, and the first set of erosion-resistant rings, so that the tube, the jacket, and the rings can move vertically independently and swivel independently about a vertical axis;
• lifting the first length of blast joint to a vertical position such that a lower end of the first set of erosion resistant rings is above a lower end of the first length of production tube, and a lower end of the first length of pressure jacket is above the lower end of the first set of erosion-resistant rings;
• threading the concentric sub into the installed production tubing which protrudes from the snubber unit;
• lowering the lifting means until the first set of erosion-resistant rings rests upon the concentric sub;
• releasing the erosion-resistant rings from the lifting means;
• further lowering the lifting means until the first length of pressure jacket contacts the concentric sub;
• threading the first length of pressure jacket onto the concentric sub;
• snubbing the first length of blast joint into the well;
• and
• releasing the pressure jacket and the production tube from the lifting means.

A hydrostatic load compensator for maintaining force on a stack of erosion-resistant rings in a blast joint to prevent separation between the rings, comprising:

• a cylindrical ratchet sleeve having circumferential ratchet grooves on the external surface thereof;
• a cylindrical pawl sleeve concentric with the ratchet sleeve and radially outward therefrom;
• a plurality of pawls extending from an end of the pawl sleeve;
• circumferential ratchet grooves on an internal surface of the pawls, meshing with the ratchet grooves on the ratchet sleeve;
• and
• a sealed enclosure located between the ratchet sleeve and the pawl sleeve maintained at a relatively low pressure, creating a pressure differential from outside the enclosure to inside the enclosure, to promote axial movement of the ratchet sleeve relative to the pawl sleeve upon increases in the pressure surrounding the load compensator.

A tube anchor for preventing relative vertical movement between a production tube and erosion-resistant rings in a blast joint, comprising:

• an inside cone cylinder sized to fit the outside of the production tube;
• threads on an external surface of the inside cone cylinder;
• a frusto-conical face on an inside surface of the inside cone cylinder;
• an outside cone cylinder sized to fit the outside of the inside cone cylinder;
• threads on an internal surface of the outside cone cylinder shaped to mesh with the threads on the inside cone cylinder;
• a frusto-conical face on an inside surface of the outside cone cylinder;
• a plurality of slip segments radially inward from the outside cone cylinder, having inwardly facing teeth;
• opposing frusto-conical faces on external surfaces of two ends of each slip segment, such faces aligning with the frusto-conical faces on the cone cylinders so that, when the cone cylinders are threaded together, the slip segments are driven radially inwardly, forcing the slip teeth into the production tube;
• and
• a circular leaf spring arranged radially inwardly from the slip segments so as to bias the slip segments radially outwardly.