E - Fixed Constructions – 21 – B
Patent
E - Fixed Constructions
21
B
166/68
E21B 36/04 (2006.01) E21B 17/00 (2006.01) E21B 43/24 (2006.01)
Patent
CA 1274172
METHOD AND APPARATUS FOR FORMING AN INSULATED OIL WELL CASING Abstract of the Disclosure A method and apparatus for forming an electrically conductive externally insulated casing for an oil well of the type in which the casing carries electrical current to a primary heating electrode positioned downhole, using multiple prefabricated casing segments; each casing segment is a long steel pipe having a female thread coupling on one end and a male thread on the other end. Each segment has an insulator covering, over substantially all of its length, that has a figure of merit Image of no more than 4 x 108 so that the the shunt impedance of the casing to ground can be kept substantially greater than the spreading resistance of the primary heating electrode. The preferred casing segment insulation is in two layers, including a hard, durable inner layer subject to water degradation and an outer water-impervious layer usually applied as tape. The uninsulated portions of joints between segments are covered with an insulator cement in the field and then further covered with a water-impervious tape that overlaps the water-impervious layers on two segments.
569743
Bridges Jack E.
Enk Joseph O.
Spencer Homer L.
Young Vincent R.
Borden Ladner Gervais Llp
Uentech Corporation
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