Abstract: A high voltage shunt regulator circuit includes a high voltage device with a predetermined reverse-conduction threshold connected in series with a thermal compensation device comprising a plurality of gate threshold amplifiers connected in series with one another. The high voltage device includes a plurality of zener diodes connected in series. Each of the gate threshold amplifiers includes a resistive voltage divider and a voltage-controlled resistive device, preferably a MOSFET. The voltage divider is formed by first and second resistors connected in series between first and second terminals of the gate threshold amplifier, with a MOSFET having its drain connected to the first terminal, its source connected to the second terminal, and its gate connected to an intermediate tap of the voltage divider.

Abstract: A &ggr;-ray tool and acoustic logging instrument combination includes in an elongated housing a transmitter for sound and at least one and preferably two, sound sensors located at predetermined distances above the transmitter. The sound sensors are separated from the sound transmitter by a steel tube that has a layer of lead bonded onto its exterior surface and has electronic components of the instrument placed into its interior. The portion of the housing that surrounds the lead bonded steel tube consists of fiberglass, polytetrafluoroethylene (TEFLON®) or other material which does not conduct sound whereby the lead-bonded tube and the immediate housing around it act as a sound isolator bar. The transmitter and the sound sensors are surrounded by portions of the housing that comprises slotted steel to allow free flow of acoustic energy through these portions of the housing.

Abstract: A select fire gun assembly for jet perforating includes a plurality of shaped charges capable of being detonated by blasting caps activated by passage of current through the cap. The first electric terminal of each blasting cap of the gun assembly is grounded. A second terminal of each blasting cap is connected through an electronic switch to the output of a diode, with the input of the diode being connected to the logging cable. The polarity of the diodes are arranged in alternative sequence. The gate of the electronic switch is also connected to the diode through a large resistor and to the ground or a dart through another resistor. These electronic switches are closed when the gate is grounded. Current can flow through the blasting cap only when the gate is grounded and when the diode associated with the blasting cap is of the appropriate polarity to allow current to pass through.

Abstract: A select fire gun assembly for jet perforating includes a plurality of shaped charges capable of being detonated by blasting caps activated by passage of current through the cap. The first electric terminal of the blasting cap on the bottom of the assembly is grounded. The remaining blasting caps are electrically connected to a dart that grounds only after the charge below has been detonated. The other terminal of each blasting cap is connected to the logging cable through a first diode, and these diodes are arranged in sequentially alternating polarity. The first terminal of each cap is also connected electrically through a large resistor to the gate of an electronic switch which is closed either by positive or negative voltage, depending on the nature of the switch. The switch is open when the gate is grounded. The electronic switch is incorporated in series with the logging cable. Positive and negative gated electronic switches are connected to the blasting caps in alternative sequence.

Abstract: A rotatable electrical connector or swivel is used in a substantially vertical subterranean portion of a drill string within a drill pipe. The swivel has an enclosed oil filled chamber having a first shaft concentrically mounted therein. The first shaft protrudes from the chamber and is electrically connected to one end of a wireline which is used for electrical connection between the surface and instruments located downhole. Within the interior of the oil filled chamber the first shaft is attached to a first member disposed within the complementary surface of a second member concentrically aligned with the first member. The second member includes a second shaft which protrudes from the oil filled chamber and is connected to the other end of the wireline. One of the two shafts is rotatably mounted in bearing within the chamber so that the complementary surfaces of the first and second members are in the relationship of a rotor and stator.