Effekt- og signaloverföring ved bruk av isolert rör til permanente installasjoner nede i brönnen

摘要

Apparatus for transmitting an electrical signal to or from a downhole device 28 in a well 1 comprises an electrically conductive conduit having an insulative encapsulation layer 30 around a section 22B of the conduit and a conduit gap 11 insulating the insulated section 22B from an adjoining section 22A of the conduit. A source 24 on the surface introduces the electrical signal within the insulated section 22A via an encoder/decoder 25 and line 60. The signal may be introduced by direct or inductive coupling. One or more devices 28 are electrically connected to the section 22B and the electrical connection is used to power the devices. The devices 28 also inject a signal into the insulated section 22B which passes via cement annulus 40, earth formation 10 and line 61 to encoder/decoder 25 which detects and records the downhole signals. Several embodiments are described.