Abstract: A percussion technique is described with which an impulse is applied to an element to bounce it off the inner surface of a casing cemented in a borehole. The movement of the element is automatically measured to produce information from which the bond between the casing and cement behind the point of impact of the element can be evaluated. In accordance with one embodiment, the cement bond evaluation is automatically derived by comparing impact and rebound velocities of the element such as by generating a coefficient of restitution of the bouncing element. In another embodiment, the contact time of the element with the casing is measured to derive an indication of the quality of the cement bond.
Abstract: Techniques for a broad band high frequency acoustic investigation of a subsurface formation around a borehole are described utilizing a range of acoustic frequencies selected to produce detectable acoustic backscatter from grains within the subsurface formation. The acoustic backscatter is detected and a spectrum thereof is produced and averaged over adjacent subsurface formation regions. A subsurface formation parameter such as the frequency dependency of the attenuation of the backscatter is determined from an analysis of the spectrum to provide an indication of the granularity property of the subsurface formation. Use of a broad range of frequencies enables a determination of the subsurface formation parameter over a large range of grain sizes. In another technique the spectrum of the detected backscatter is modified to remove the effect of the frequency response of the system with which the investigation is made.
Abstract: In accordance with an illustrative embodiment of the present invention, a valve placed in a subsea blowout preventer stack during a production test of a well producing gas comprises a valve body containing two valve elements in series and a releasable control unit. A fluid to inhibit the formation of natural-gas hydrates can be injected into the valve body by means of a pump on the surface and through a high-pressure hose. A lateral connector fixed to the control unit is fitted in a sealed manner into a receptacle on the valve body to allow reconnection of the inhibiting fluid injection system.
Abstract: In accordance with an illustrative embodiment of the present invention, a new and improved valve system for retaining production fluids in the subsea production pipe upon disconnection of the riser from the subsea wellhead during a production test of an offshore well includes a normally closed valve releasably connected to a normally open valve. The normally open valve can be hydraulically closed from a remote control station upon disconnection of the riser in order to retain fluids in the production pipe thereabove, and when closed will hold pressure in either longitudinal direction.
Abstract: In accordance with an illustrative embodiment of the present invention, a shock limiting apparatus for mounting an instrumentality in a drill collar comprises piston and cylinder means subject to hydrostatic well fluid pressure for preventing longitudinal movement of the instrumentality within the drill collar unless a predetermined level of deceleration is exceeded, and a combination of hydraulic damping and Coulomb friction means for dissipating kinetic energy of the instrumentality in a substantially uniform manner when applied deceleration exceeds said predetermined level.
Abstract: The disclosure is applicable for use in a logging-while-drilling apparatus for obtaining subsurface measurements during drilling in a fluid-filled borehole. Acoustic carrier waves are generated downhole in the borehole fluid and are PSK modulated in accordance with digital data representative of downhole measurements. The PSK modulation is obtained by momentarily unidirectionally either decreasing or increasing the frequency of the acoustic carrier signal until either a desired phase lag (for a decrease in frequency) or phase lead (for an increase in frequency) is imparted to the acoustic carrier signal. An uphole receiving subsystem includes transducers for converting the modulated acoustic carrier waves to electronic signals and circuitry for demodulating the electronic signals to recover the measurement information taken downhole. In accordance with an important feature of the invention, a filter is provided for selectively filtering the electronic signals before the demodulation thereof.
Abstract: The disclosure is applicable for use in a logging-while-drilling apparatus for obtaining subsurface measurements during drilling in a fluid-filled borehole. Acoustic carrier waves are generated downhole in the borehole fluid and are PSK modulated in accordance with digital data representative of the measurements. The PSK modulation is obtained by momentarily unidirectionally either decreasing or increasing the frequency of the acoustic carrier signal until either a desired phase lag (for a decrease in frequency) or phase lead (for an increase in frequency) is imparted to the acoustic carrier signal. An uphole receiving subsystem includes transducers for converting the modulated acoustic carrier waves to electronic signals and circuitry for demodulating the electronic signals to recover the measurement information taken downhole.
Abstract: A lubricator valve apparatus adapted for use when running wireline tools into an offshore well during a production test of the well. The valve includes a valve body having a central flow passage and a ball valve element for opening and closing the passage, hydraulically operable means responsive to surface-controlled pressure for opening and closing the ball valve, latch means for releasably holding the ball valve in both the open and the closed positions, and bypass valve means for equalizing pressures across the ball valve prior to opening thereof and arranged in the event hydraulic control of the ball valve is lost to be opened in response to pressure applied at the surface to the production pipe to provide a flow path for well control fluids.
Abstract: A variable filter having a plurality of different loopwidths is disclosed. The variable filter, which is typically employed in a phase locked loop, includes a plurality of capacitors which are switchably coupled into and out of operation in the filter in order to change loopwidths. Those of the capacitors which are not currently operational in the filter are precharged so as to prevent loss of lock in the phase locked loop when switching to another loopwidth.
Abstract: A radio control system for controlling model airplanes, model boats and the like. The system includes a multi-channel transmitter and a multi-channel receiver each operative on the same assigned radio control frequency. The system operating frequency is changeable by exchanging both a small pluggable transmitter module and a small pluggable receiver module with a different transmitter and receiver module respectively, the latter modules being operative on an assigned radio control frequency different from that of the former modules. The system provides quick and easy change of the operating frequency thereby permitting simultaneous radio control of many models via many such systems operating on non-interfering radio control frequencies.
Abstract: In accordance with an illustrative embodiment of the present invention, the respective volume flow rates of a gas and a liquid flowing in a conduit are determined by measuring the total volume flowrate, the pressure and the temperature of the two-phase mixture at first and second spaced points in the conduit, creating a pressure drop in the conduit between the first and second points, and determining the respective volume flowrates of the gas and liquid utilizing the measured values of total volume flowrates, pressures and temperatures. The invention has particular utility in well testing.
Abstract: A measuring-while-drilling system having a downhole, motor-driven acoustic signal generator includes a motor speed control circuit featuring feedback compensation which accounts for varying loading conditions on the motor. The acoustic signal generator is motor driven at speeds for imparting to well fluid an acoustic signal having phase states representative of data derived from measured downhole conditions. The motor control circuit includes circuitry which forms a phase locked loop for driving the motor at a reference phase and at a substantially constant carrier frequency producing speed in the absence of data of one logic state and also includes circuitry for temporarily changing the speed of the motor, according to a pre-programmed function, to effect a predetermined amount of phase change in the carrier signal upon data of the predetermined logic state.
Abstract: The disclosure relates to an apparatus for receiving a carrier signal modulated with digital symbols, the symbol rate being related to the carrier frequency, such as by a submultiple or a ratio of integers. The invention is an adaptive carrier-aided symbol tracking loop in which signals derived from a symbol-coherent carrier maintain and aid symbol synchronization during periods of no symbol transitions. The invention is particularly applicable to systems wherein the received modulated carrier signal has been transmitted over a noisy transmission path, such as in a logging-while-drilling system. In accordance with the invention there is provided a phase-locked loop which includes a voltage controlled oscillator and an error signal generator for controlling the oscillator. In response to the carrier, a first signal is generated at substantially the symbol rate and, in response to symbol transitions, a second signal is generated which has a phase that depends upon symbol transitions.
Abstract: A deflection amplifier for driving a magnetic-deflection cathode-ray tube in a digital plotter has two switching circuits coupled to low- and high-voltage supplies respectively. An error amplifier compares the actual deflection-coil current, as indicated by the voltage developed across a resistor in series with the coil, with the command input voltage indicating the required current. As long as the difference between required and actual currents is less than a predetermined threshold value, only the low-voltage switching circuit operates, thereby limiting power dissipation. However, if the current difference exceeds the threshold value for at least 2.mu.s, the high-voltage switching circuit commences operation to supplement the drive provided by the low-voltage circuit. The high-voltage circuit is limited by logic circuitry to periods of operation 20.mu.s long with a 5.mu.s quiescent period between each. The low- and high-voltage supplies are bipolar, and corresponding bipolar threshold values are provided.
Abstract: Disclosed is a watthour meter box which allows simple disconnection of the meter and which includes a meter socket rotatably engaging the meter and a housing structure permitting the meter to be rotated from a first position where the meter is fully connected electrically to the meter socket to a second position where the meter is not fully connected electrically to the meter socket. In a preferred embodiment, the invention includes a stationary front panel having an oblong opening to admit the glass portion of the watthour meter and a movable plate behind the front wall having a similar oblong opening with a gasket reducing the opening to match substantially the perimeter of the glass wall of the meter. By releasing means securing the position of the movable plate, the meter rotates about a pivot member in the lower jaws of the socket and disengages its upper prongs from the upper jaws. Also disclosed are means securing the movable plate in the second disengaged position.
Abstract: A technique for converting video information into sequences of digital words in a form which can be readily accepted by a computer. The generated digital words exclude some information content of the video signals which is not necessary for certain pattern recognition and control purposes. In accordance with the preferred embodiment of the invention, there is provided a clock having a rate which is in synchronism with the video line and field information. A comparator is provided for comparing the video signals to a prescribed standard and for generating digital indications as a function of the comparisons. Each digital indication is preferably a binary bit which indicates whether the compared video signal is above or below the prescribed threshold. Means, synchronized with the clock rate, are provided for serially accumulating a predetermined number of successive digital indications. Finally, means are provided for reading out each group of accumulated digital indications.
Abstract: In accordance with an illustrative embodiment of the present invention as disclosed herein, a combination slip joint-safety valve tool includes telescoping mandrel and housing members, a full-opening valve on the housing member operable when closed to prevent upward flow of fluid through said members, and hydraulically operable valve actuator means responsive to contraction of said telescoping members for closing said valve and to extension of said members for opening said valve.
Abstract: A method and apparatus are described for preferentially exciting and for extracting late arrivals at low frequencies in an acoustic investigation of a borehole. The late arrival may be the Stoneley wave whose amplitude is derived by measuring the energy in a predetermined frequency band of a waveform produced with a low frequency transmitter-receiver system. The transmitter produces a highly damped acoustic pulse whose frequency spectrum is selected to preferentially excite a late arrival such as the Stoneley wave and/or tube wave with wavelengths which are significantly greater than the diameter of the borehole while preserving measurable earlier arrivals at higher frequencies. A receiver system is used which provides a generally flat frequency response including low frequencies to produce waveforms of both the earlier arrivals at high frequencies and late arrivals at low frequencies with sufficient extractable amplitudes throughout a wide range of borehole and formation conditions.
Abstract: In the representative embodiments of the present invention described herein, a drilling mud is circulated through a drill string at a sufficient rate to effectively operate an impeller-driven electrical generator arranged on a tool coupled in the drill string for supplying power to downhole electrical circuits and one or more downhole condition-measuring devices on the tool. By selectively controlling the flow of drilling mud past the impeller in accordance with the conditions being monitored by the condition-measuring devices, data-encoded acoustic signals are produced in the circulating fluid and transmitted to the surface for detecting and decoding as power is simultaneously supplied to the downhole system by the generator.