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: Binary bits that are represented by pulses are identified by circuitry that integrates a signal having a sequence of such pulses for the period of each bit pulse. At the end of the integrating period, the integrator level is stored, and the integrator is discharged. Storage and discharge are synchronized with the bit pulse rate by an oscillator whose frequency is varied until the integrator level is maximized. The presence of a bona fide signal bit is indicated by a predetermined integrator level. A false signal bit generated as part of the background noise will not endure long enough to cause the integrator to reach the predetermined level of a bona fide bit.

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: 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: 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.