Joseph O Enk

46462775, Feb 24, 1987

Apr 12, 1985

6/722807

Jack E. Bridges - Park Ridge IL
Joseph O. Enk - Lake in the Hills IL

Gas Research Institute - Chicago IL

F21B 4400
F21B 47022
B23Q 500

367191

A control system guides a boring tool in a borehole. The tool has a longitudinal tool axis and includes a driver for advancing the tool axially through the earth and steering mechanism for directing the motion of the tool relative to the tool axis in response to control signals. The control system includes an axial electromagnetic source for generating an axial alternating magnetic field directed along an axial source axis. A sensing assembly remote from the source means includes first and second pickup coils for sensing the alternating magnetic field. Each of the first and second pickup coils has a respective coil axis and is rigidly mounted in respect to the other with their respective axes at a substantial angle with respect to each other, defining a sensing assembly axis substantially normal to both coil axes. Each coil generates a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis. Either the source of the sensing assembly is rigidly mounted on the tool, preferably the source.

47934093, Dec 27, 1988

Jun 18, 1987

7/064063

Jack E. Bridges - Park Ridge IL
Joseph O. Enk - Lake in the Hills IL
Homer L. Spencer - Tulsa OK
Vincent R. Young - Tulsa OK

ORS Development Corporation - Tulsa OK

E21B 1916
E21B 3600
F16L 914
H05B 302

166 57

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 (erl)/. DELTA. of no more than 4. times. 10. sup. 8 so that 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, durarable 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 withan insulator cement in the field and then further covered with a water-impervious tape that overlaps the water-impervious layers on two segments.