Remote well signalling apparatus and methods

摘要

Information is conducted upwardly from a location deep within a well by a transmitter which is located in the well and induces electrical currents in the surrounding earth formation. These currents are sensed at an upper location by readout equipment connected to two electrodes which are in electrical contact with the earth at spaced locations. One of the electrodes is at a subsurface location and is connected to the readout equipment by an insulated conductor. In offshore drilling situations, the specified subsurface electrode is at the very least located beneath the surface of the ocean or other body of water through which the well extends, and in most instances is preferably embedded within the earth formation under that body of water, and at a location spaced beneath the seabed. In a presently preferred arrangement, the information which is carried by the electrical signals in the earth is generated by an instrument in the well having both a magnetically actuated sensor and a gravity actuated sensor for indicating the directional orientation of a drill string in the well. These sensors may be adapted to be turned to different rotary settings relative to a carrier structure, to enable pre-setting of the sensors in proper orientation relative to a connected directional drilling assembly.