Blast joint for subterranean wells

Abstract

This is an improved blast joint for subterranean wells which is ideally suited for applications where corrosive compounds such as hydrogen sulfide and carbon dioxide are encountered. The blast joint comprises a plurality of temperature and corrosion resistant hard rings which are in a stacked end face-to-face array, coaxially carried on a length of tubing. The rings are resiliently compressed in the array by spring washers interspaced by flat washers and this assembly is retained by end collars distally carried on the tubing. The end collars which are employed in this invention have a collet type construction; each collar comprising a clamp ring slidably received over the end of the production tubing, having an internally threaded outer end and a tapered inside wall. A collet sleeve with a tapered outside wall is received in the clamp ring. The collar also includes an externally threaded bushing which is received in the threaded outer end of the clamp ring and serves as an axial stop for the collet sleeve as the clamp ring is tightened, compressing the collet sleeve about the outer surface of the tubing, firmly locking the assembly. All members of the collar are coated with a protective, corrosion resistant coating and the gripping surfaces of the collet sleeve are coated with a resin that is filled with angular granular material of a high hardness.