Patent ID: 8680866

Claim:
An electromagnetic energy transmitter mounted with a wireline for conducting borehole to surface electromagnetic surveys of subsurface earth formations from a well borehole with electromagnetic field responses sensed by an array of receivers at the earth surface as a result of electric current flow from the transmitter, the borehole having a casing installed along its extent into the earth to a location near a formation of interest, the casing being formed of lengths of tubular members connected at end portions to adjacent tubular members by casing collars, the transmitter comprising: a conductive bar emitting electric current to travel through the earth form the well borehole through the subsurface formations when activated; a control circuit activating the conductive bar to emit electric current for a selected time and duration; a sonde body housing the control circuit and being lowered by the wireline in the well borehole to the location near the formation of interest; the conductive bar being mounted to the sonde body below the sonde body; an upper connector subassembly mounted above the sonde body connecting the control circuit to the wireline and permitting the flow of electrical current to the conductive bar; a lower connector subassembly below the sonde body connecting the conductive bar to the control circuit; a casing collar locator mounted in the sonde body and providing indications of the movement of the sonde body past casing collar in the casing during movement of the transmitter through the well borehole; a fluid pressure sensor mounted in the sonde body for monitoring fluid pressure in the well borehole at the location of the sonde body during the borehole to surface electromagnetic surveys; and a temperature sensor mounted in the sonde body for monitoring temperature in the well borehole at the location of the sonde body during the borehole to surface electromagnetic surveys.