Abstract: An apparatus for detecting mud pulse telemetry signals includes a differential transducer. In various exemplary embodiments, a high-pressure side of the differential transducer is in fluid communication with either drilling fluid in a standpipe (which is in fluid communication with drilling fluid in the borehole) or a gas chamber of a pulsation dampener. Exemplary embodiments typically further include a pressure delay module in fluid communication with the low-pressure side of the differential transducer and the gas chamber of the pulsation dampener. The invention is intended to advantageously improve the reliability and bandwidth of mud pulse telemetry communications in oilfield drilling applications.

Abstract: A well logging apparatus is disclosed having an elongate body supporting a plurality of antenna coils housed in recesses formed on the body. A sleeve covers the segment of the body containing the antenna recesses and seals the antennas from borehole fluids. Electronics compartments formed in the body for housing signal conditioning circuitry are likewise sealed by the sleeve. The sleeve includes slotted regions filled with a sealant, the slotted regions being disposed about the antenna coils and providing an electromagnetically transparent window through the sleeve.

Abstract: A logging-while-drilling system is disclosed which includes a pair of receiving antenna disposed between upper and lower transmitting antenna. The upper and lower transmitting antenna are energized successively to generate an electromagnetic wave which propagates through the formation surrounding the borehole. The amplitude attenuation and phase shift of the electromagnetic wave between the receiving antenna is measured. Measurements from both the upper and lower transmitting antenna can be combined to eliminate by cancellation system error components. In order to further improve the performance of the logging-while-drilling system, separate and dedicated driver circuits are provided proximate each transmitter. In addition, reference signals which are utilized to coordinate and synchronize the operation of the various components of the logging-while-drilling system are provided at frequencies which are substantially different from the interrogation frequency of the electromagnetic interrogation signal.

Abstract: Variable control of the stroke and timing of the poppet in a pressure pulse generator system provides desired control for varying down hole conditions. A stepper motor interconnected to the poppet provides variable acceleration and variable position for the poppet under the control of a motor controller and motor driver which establish the number of steps and timing of steps for the motor. Various valve position profiles are provided in a memory for specific stroke and acceleration operation of the valve under varying down hole conditions and signaling requirements.

Abstract: A well logging apparatus and method for measuring the resistivity of the formation surrounding a borehole is disclosed. The invention provides two transmitting antennas arranged around a housing means or drill collar in spaced relation from one another. A transmitting circuit alternately supplies an oscillating drive signal to each transmitting antenna with a sufficiently high frequency such that one and then the other of the transmitting antennas radiates an electromagnetic wave signal which propagates through the formation. Two receiving antennas are located equally spaced between the transmitting antennas to produce pick-up signals from the electromagnetic wave propagating through the formation. Each receiving antenna includes a single turn coil connected in series with a capacitor to provide a reduced impedance circuit to resonate in the frequency region embracing the oscillating drive signal.

Abstract: Improved radioactivity well logging by mounting a scintillator and photomultiplier tube in a single case interfacing with a hole extending through a drill collar at the lower end of a drill string so that measurements can be made while drilling. Radioactive sources (when required for well logging) are mounted in cavities which open to the exterior of the drill collar. Light from the scintillator is coupled directly to the aligned photomultiplier tube both of which are mounted in a case extending radially within the drill collar and sealingly engaging an electronics housing within the drill collar and the drill collar wall surrounding the hole. The scintillator is of greater diameter than the photomultiplier tube. A frustoconical light pipe connects the scintillator and the photomultiplier tube, channeling scintillation in the crystal to the photomultiplier to provide an amplified detection capability over that for a scintillator having the same diameter as the photomultiplier tube.

Abstract: Improved radioactivity well logging by mounting a scintillator in a hole extending through a drill collar at the lower end of a drill string so that measurements can be made while drilling. Radioactive sources (when required for well logging) are mounted in cavities which open to the exterior of the drill collar. Light from the scintillator is coupled through a right-angle prism or fiber optics through an angle of about 90.degree. so that an elongated photomultiplier tube can be mounted within a housing within the drill collar with the longitudinal axis of the photomultiplier tube extending substantially parallel to the axis of the drill collar to provide maximum cross sectional area for flow of drilling fluid with the housing in the drill collar.

Abstract: Apparatus for sending pressure pulses through drilling fluid in a drill string in a well bore includes an assembly adapted to be lowered from the surface through the drill string to a position adjacent the lower end of the drill string. The external dimension of the assembly is substantially less than that of the internal diameter of the drill string, so there is always a substantial clearance between the assembly exterior and the drill string interior to permit a substantial flow of drilling fluid down the drill string, past the assembly, through a drill bit, and into an annular space between the drill string exterior and the well bore. The assembly includes an internal bore to permit drilling fluid to flow through the assembly. Means are provided for intermittently restricting flow of drilling fluid through the assembly bore to send the pressure pulses to the surface in response to the magnitude of a downhole condition to be measured.

Abstract: Apparatus for sending pressure pulses through drilling fluid in a drill string in a well bore includes an assembly adapted to be lowered from the surface through the drill string to a position adjacent the lower end of the drill string. The external dimension of the assembly is substantially less than that of the internal diameter of the drill string, so there is always a substantial clearance between the assembly exterior and the drill string interior to permit a substantial flow of drilling fluid down the drill string, past the assembly, through a drill bit, and into an annular space between the drill string exterior and the well bore. The assembly includes an internal bore to permit drilling fluid to flow through the assembly. Means are provided for intermittently restricting flow of drilling fluid through the assembly bore to send the pressure pulses to the surface in response to the magnitude of a downhole condition to be measured.

Abstract: A monostable, solenoid-operated valve in a passage which bypasses the drilling fluid pressure drop across a drill bit at the lower end of a drill string in a well opens and closes in response to downhole conditions to create pressure pulses in the drilling fluid. The valve is urged toward a closed position by drilling fluid pumped through the drill string. A larger force is required to open the valve than to hold it open. Current supplied to the solenoid to open the valve is thereafter reduced to a value sufficient to hold the valve open. The solenoid is de-energized to close the valve.

Abstract: A monostable valve for insertion in a drill string used in forming a borehole such as an oil well. In an open position, the valve vents drilling fluid flowing in the drill string to an annulus in the borehole for return flow to the surface, thus generating a surface-detectable negative fluid-pressure pulse. A valve closure member is supported for horizontal movement to provide significant isolation from vertical accelerations occurring during drilling, and the closure member and associated valve seat are field replaceable. Primary power for valve actuation is drawn from the drilling-fluid hydraulic energy as controlled by a low-power solenoid-actuated pilot valve.