Simultaneous logging system for deep wells

TLDR: In this paper, an improved well logging system of the type utilizing a single conductor cable to provide power from the surface equipment to a down hole subsurface unit and for simultaneously supplying current mode telemetry signals from one or more radiation detectors in the subsural unit to the surface devices is presented.

Abstract: An improved well logging system of the type utilizing a single conductor cable to provide power from the surface equipment to a down hole subsurface unit and for simultaneously supplying current mode telemetry signals from one or more radiation detectors in the subsurface unit to the surface equipment. The surface equipment includes a power supply for the subsurface unit comprising a constant current source having a high output impedance connected to a series pass voltage regulator having a low output impedance. A switching mode voltage regulator is employed within the subsurface unit to compensate for variations in the voltage supplied to the subsurface unit which result from variations in cable resistance and other factors. The subsurface unit includes circuitry capable of operating at the high temperature encountered in deep wells for an extended period of time and which transforms the detector output signals into corresponding current mode telemetry signals which are supplied over the single conductor cable to the low impedance output terminals of the series pass voltage regulator at the surface. The current mode signals are transformed by the series pass voltage regulator and appear as amplified voltage signals at the high impedance junction of the constant current source and the series pass regulator. Demultiplexing and recording circuitry is connected to the aforementioned junction to receive the amplified voltage signals and develop corresponding rate meter signals which may be applied to a recorder in the surface equipment.