Abstract: A single shot surveying instrument which is designed to be lowered to a desired location in a borehole and to take a single picture which indicates the direction of the borehole. The instrument operates in a first mode in which a picture is taken after the passage of a preselected period of time, which period is selected to allow sufficient time for the instrument to be properly positioned in the borehole. The instrument also operates in a second mode in which a picture is taken after the lapse of the preselected period of time if there is an absence of motion by the instrument during a last portion of the preselected time period. An indicator light on the instrument provides a check for premature operation of the instrument and for operability of the motion sensing capability.

Abstract: A sub for use in an acoustic telemetry system provides a sound path of low impedance to facilitate the transmission of acoustic signals through a string of pipe positioned in a wellbore. The sub section of pipe includes a tubular receiving member positioned in the bore of a pipe section and spaced from the interior walls thereof. Ports and flow channels are also provided to permit the passage of well fluids through the pipe section when an acoustic instrument is positioned in the tubular receiving member. A lateral shoulder is formed in the interior wall of the receiving member and is arranged to matingly receive a flat portion on the instrument. The abutment of the flat portion of the instrument and the shoulder provides a positive sound path for transmission of longitudinal sound waves from the instrument to the receiver member.

Abstract: Inclination and high side angle of a borehole is measured by a tool that may be positioned inside a drill string and lowered into the borehole. The tool includes three gravity transducers positioned in a novel array. The transducers are positioned in a case whose axis coincides with that of the borehole and are arranged with their axes angularly displaced from each other around the case axis by approximately 120 degrees and from the case axis by approximately 45 degrees. An array of fluxgate magnetic transducers may be added to the apparatus to provide combination surveying and steering capability.

Abstract: Information as to borehole inclination is provided by a pendulum in combination with an elastomeric material whose resistance varies with compression. The pendulum is arranged in a housing to compress the elastomer whenever the housing deviates from the vertical, or other predetermined attitude. The change in resistance is measured by a circuit including an ohmmeter and the pendulum and elastomer as conductive elements.

Abstract: A lock-in filter that may be used to detect an AC data signal in the presence of high level noise signals that may occur in such systems as those used for acoustical telemetry in boreholes includes a pair of parallel capacitors receptive of the data and noise signals and circuitry operating in response to signals in the capacitors for alternately switching the capacitors to receive the noise and data signals in phase with the data signal.

Abstract: Borehole pressure is measured with an open-ended chamber positioned in the borehole and in fluid communication with a surface pressure source through a microtube. The chamber contains a ball float that seats in the upper end of the chamber to seal the microtube to entry of borehole fluids. The ball is made of a material having a density greater than that of the borehole fluids in order that the float can withstand high pressures. Partial support to compensate for the high density material of the float is provided by a spring attached between the chamber and the float ball.

Abstract: A pressure measurement system particularly suited to use in boreholes uses a pressure source at the surface to supply a test fluid through a small tube to a large downhole chamber having a fluid port on its bottom side. The test fluid displaces borehole fluid from the chamber after which the pressure of the test fluid is measured at the surface, thereby indicating the pressure of the borehole fluid.

Abstract: An unknown pressure at a remote location, such as in a borehole, is sensed by passing a fluid at a constantly increasing pressure, into a pressure sensitive device at the remote location. The pressure is monitored at the measurement location until a characteristic change in the rate of pressure buildup in the pressure sensitive device occurs. Effects of fluid supply pressure on the monitoring device are minimized in relation to buildup pressure in the pressure sensitive device by placing a flow control valve between the supply pressure source and the buildup pressure monitor.

Abstract: Methods of gravel packing are disclosed utilizing controlled melting point materials with the gravel placed behind a liner located in the wellbore. The controlled melting point materials can be coated on the gravel prior to its placement behind the liner or circulated behind the liner separate from the gravel. After placement of the gravel and controlled melting point material behind the liner, heat is provided to melt the material so that it acts as a consolidating agent.

Abstract: A system for measuring the rotation of a shaft without direct mechanical connection to it uses a digital system to maintain a second shaft that connects to a cylindrical chart recorder in a constant angular position relationship with the measured shaft. Two limit switches on the recorder shaft sense the rotation of a reference point on the measured shaft beyond a range defined by the location of the limit switches. A stepper motor driven by digital power supply incrementally rotates the recorder shaft to move a reference point on the recorder shaft back into alignment with the reference point on the measured shaft. A digital counter controls the number of pulses supplied by the power supply to stop the recorder shaft in the aligned position.

Abstract: A buoyant, cylindrical metal drum, having a plurality of elongate teeth protruding outwardly from the periphery thereof is mounted for rotation about its longitudinal axis in a generally U-shaped framework. The frame is pivotally attached to the front of a tug vessel and the drum may be steered, with respect to the boat, by moving the mounting frame about the pivot point. An internal power source and an eccentric counterweight, which may include a fuel storage container for the power source, are stationarily mounted within the drum which is rotated about the counterweight as an inertial reference. When the drum is rotated by its internal power source and moved against the water/ice interface of a floating arctic ice sheet, the moving teeth on the drum cut the ice and clear a path for movement of the drum and the tug boat through the ice covered water.

Abstract: A slope change detector circuit uses a differential amplifier to produce an output signal having two levels, the change of one to the other of which is indicative of a slope change in an input electrical signal. A first input of the differential amplifier communicates directly with a signal source, while a second input communicates with a signal source through a delay network. The delay network includes a switching circuit between the signal source and the differential amplifier comprising a field-effect-transistor and a capacitor; and a feed back circuit comprising a circuit that derives the absolute value of the differential amplifier's output signal and a level detecting zener diode that causes the field effect transistor to change resistance when the absolute value signal reaches a predetermined level.

Abstract: Buoyant bodies such as those used for drilling oil and gas wells in water-covered areas are moored to the floor of the body of water with lines in the catenary configuration. Rotational motions induced by such configurations are reduced by providing for vertical adjustment in the point of attachment of the lines on the buoyant body.

Abstract: A circuit for linearizing the power output of a thyristor uses a threshold switch to pulse the thyristor into the conducting mode. An accumulating capacitor provides a current to operate the threshold switch. The current that charges the accumulating capacitor arises in a DC amplifier and absolute value of sine current source. The accumulating capacitor may discharge either through the threshold switch or through a shunt switch if the threshold has not been attained within a predetermined time period. The timing device for the shunt switch is a sync pulse supply that keys off the absolute value of sine current source.

Abstract: A zeroing circuit for use in conjunction with devices that produce output signals in response to input data signals feeds a compensating signal into such a device to produce a zero output signal when there is a zero input signal. The device being compensated is intermittently tested for the zero condition, and an aspect of the compensating signal is altered to produce the zero condition.

Abstract: A detector having particular utility in a gas chromotograph uses a sensor to produce signals indicative of parameters of components of a gas. A signal whose level is related to a gas parameter is generated and sent to an amplifier. The output of the amplifier is stored and a signal related to the amplifier output signal is sent by means of a feedback loop to the input of the amplifier to compensate for losses in the amplification and storage processes.