| 摘要 |
<p>Electromagnetic cased well information transmission comprises electrical insulation of metal casing tubes adjacent low resistivity formation layers. Information transmission from a cased well, using a downhole transmitter/receiver operating by guided electromagnetic waves created by electrical signal injection by a dipole connected to the metal casing tubes which guide the emitted waves comprises identifying low resistivity formation layers which cause transmission attenuation, and electrically insulating the tubes located at these layers. An Independent claim is also included for a system for carrying out the above information transmission method. Preferred Features: A mathematical model is used to calculate the minimum length to be insulated, taking into account the minimum characteristics of the electromagnetic transmission, especially the transmission distance and/or the information output rate. Insulation is effected by providing a cement-type insulating material in the gap between the casing tubes and certain formations. The transmitter/receiver is positioned near the lower end of a production tubing string, for transmitting bottom measurements or bottom equipment commands, or is positioned near the lower end of a well casing for transmitting bottom or drilling parameters or location measurements.</p> |
