Insulated section of oil well steam injection string - has thermally expanded inner tube welded to outer tube, coupling by screw sleeve

摘要

The insulated tube sections are intended for coupling to form a tube string for placing into a (cased) bore hole to inject steam into an oil-bearing formation. It comprises a thermally expanded inner tube (21) inside an outer tube (25) with insulating material (28) and spacer rings (not shown) in the annular space (27) between them. End rings (22) first secured (23,24) around the tube (21) near its ends (35) are internally secured (26) to the ends of the tube (25) whilst the tube (21) is in its expanded condition, after which male (taper pipe) thread (32) is cut on the tube (25) ends for intercoupling double-walled insulated tube sections so produced by means of coupling sleeves (31) having corresp. female screw thread (33) at their ends. Insulated double-walled tube sections for steam injection (or hot product extn.) tube string in bore hole of oil well. Pre-insulated tube sections, which are preferable because in-situ insulation precludes inspection after installation, suffer from heat loss via the couplings, which is prevented by the design of this disclosure. Pre-expansion of the inner tubes avoids excessive stresses in operation, thus reducing risk of fatigue failure.