Abstract: A downhole system comprises a main sensor, such as a gamma sensor, and a backup sensor. The backup sensor may be of a different type from the main sensor. In some embodiments the backup sensor is a high reliability sensor that may have a different sensitivity from the main sensor. The system operates both the main and backup sensors and generates calibration data for the backup sensor. If the main sensor fails the calibration data may be applied to process data from the backup sensor to yield an estimate of the data that the main sensor would have yielded if it had remained operational. The calibration data may compensate for temperature variations and/or temporal drift, for example.

Abstract: A fluid pressure pulse generator comprises a stator having a body with a cylindrical bore and a fluid flow chamber comprising a lateral opening and an uphole axial inlet, and a rotor having a cylindrical body rotatably seated within the bore, a rotor head connected to the rotor body, and a fluid diverter comprising a fluid passage through the rotor body and a nozzle in the rotor head. A fluid passage has an opening on an outside surface of the rotor body and an outlet at an end of the rotor body. The nozzle has an inlet end communicable with a drilling fluid and an outlet end in fluid communication with the fluid opening. The flow area of the nozzle increases from the inlet to outlet end such that the velocity of the drilling fluid slows while from inlet to outlet end.

Abstract: An electromagnetic telemetry signal generating assembly comprises a first section of drill string, a second section of drill string, a gap sub configured to insulate the first section from the second section, and a power source configured to provide a first voltage to a control circuit. The control circuit is configured to drive a second voltage between the sections of drill string. The gap sub provides a gap of at least 12 inches (30 cm). The second voltage may be different than the first voltage.

Abstract: Methods, techniques, and systems for transmitting a data frame of an electromagnetic (EM) telemetry signal to or from a downhole location can be performed using multi-channel transmissions in which at least two different channels at two different frequencies are used to send a long header and the data frame. At least a portion of the long header is transmitted at a first frequency, and at least a portion of the data frame and any remaining portion of the long header not transmitted at the first frequency are transmitted at one or more additional frequencies different from each other and the first frequency. In one example, only two channels are used: one channel is used to transmit all of the long header, another channel is used to transmit all of the data frame, and either of the channels is used to transmit an identifier identifying the type of the data frame.

Abstract: An assembly for receiving telemetry signals from downhole equipment is located at a top end of a drill string above a drill rig floor. The assembly may be configured to receive multiple types of telemetry signals, for example, two or more of electromagnetic telemetry, mud pulse telemetry and drill string acoustic telemetry signals. The assembly may comprise a cap comprising a coupling and an end separated by an electrically insulating gap region. The end of the cap may be connected to a grounding system for the drill rig.

Abstract: A component mounting apparatus for holding a rigid component in a downhole bore or a downhole collar based application includes a first body including first and second parallel spaced apart component holders disposed in a first common plane and a first support connecting the component holders together. The first and second parallel spaced apart component holders are operable to receive and grip a rigid component between the first and second parallel spaced apart component holders. Various component mounting assemblies and configurations may be realized using the component mounting apparatus described. The component mounting apparatus and various mounting assemblies may be used to mount a printed circuit board in a cylindrical enclosure or tubular housing, for example.

Abstract: A fluid pressure pulse generator comprises a stator with a body and cylindrical bore and a generally cylindrical rotor having uphole and downhole ends with different diameters to form an annular fluid barrier at the intersection of the two ends. An annular gap is formed between the rotor uphole end and stator body. The stator body and rotor body collectively have a fluid flow chamber comprising a lateral opening and an uphole axial inlet, and a downhole axial outlet and fluid diverter comprising a lateral opening in fluid communication with the axial outlet. The annular fluid barrier is in fluid communication with the fluid flow chamber or the fluid diverter. The rotor can be rotated such that the fluid diverter is movable in and out of fluid communication with the fluid flow chamber to create fluid pressure pulses.

Abstract: A fluid pressure pulse generator comprises a stator having a body and cylindrical bore and a rotor having a cylindrical body and cap. The diameter of the cylindrical body is smaller than that of the stator central bore such that an annular gap is formed therebetween. The cap has a base with a diameter larger than that of the rotor body, forming a protruding lip that covers at least a portion of the annular gap. The stator body and rotor body collectively have at least one fluid flow chamber comprising a lateral opening and an uphole axial inlet, and a downhole axial outlet and at least one fluid diverter comprising a lateral opening in fluid communication with the axial outlet. The rotor can rotate within the stator such that the fluid diverter moves in and out of fluid communication with the fluid flow chamber to create fluid pressure pulses.

Abstract: A fluid pressure pulse generator comprising a stator and rotor that can be used in measurement while drilling using mud pulse or pressure pulse telemetry is disclosed. The stator comprises a stator body with a circular opening therethrough and the rotor comprises a circular rotor body rotatably received in the circular opening of the stator body. One of the stator body or the rotor body comprises one or more than one fluid opening for flow of fluid therethrough and the other of the stator body or the rotor body comprises one or more than one full flow chamber. The rotor is rotatable between a full flow configuration whereby the full flow chamber and the fluid opening align so that fluid flows from the full flow chamber through the fluid opening, and a reduced flow configuration whereby the full flow chamber and the fluid opening are not aligned.

Abstract: A downhole system has a plurality of telemetry systems and a control system configured to obtain information from one or more sensors and transmit that information on one or more of the plurality of telemetry systems. The configuration of a controller may be changed so as to change which information is transmitted on a given telemetry system and how the information is to be transmitted on the given telemetry system.

Abstract: A system for charging a capacitor used to power measurement-while-drilling equipment includes a power bus, which is electrically connected to the capacitor; a first pair of battery terminals; switching circuitry for electrically connecting the power bus to and disconnecting the power bus from the first pair of battery terminals; and a controller, for controlling the switching circuitry, which is configured to charge the capacitor by applying a first pulse width modulated control signal to control the switching circuitry. The first pulse width modulated control signal has a duty cycle selected such that the voltage of the first battery remains above a first minimum operating voltage while the capacitor is being charged.

Abstract: A method and apparatus for joining first and second bodies coaxially together to resist relative axial and rotational movement between the bodies. A male portion of the first body is received in a complementary female portion of the second body, and the male and female portions are aligned axially on a common axis such that respective cooperating grooves in opposing cylindrical or tapered complementary surfaces of the male and female portions are aligned to form a plurality of passageways or a passageway having a plurality of passageway portions, between the opposing cylindrical or tapered complementary surfaces. At least two of the passageways or at least two of the passageway portions are disposed at different angles to the common axis.

Abstract: A method for modulating a downhole telemetry signal uses a fluid pressure pulse generator that generates pressure pulses of multiple pulse heights in a drilling fluid. The method comprises: converting measurement data into a bitstream comprising symbols of a selected symbol set; encoding the bitstream into a pressure pulse telemetry signal using a modulation technique that includes amplitude shift keying, wherein each symbol of the selected symbol set is assigned a pressure pulse having a unique amplitude; and generating pressure pulses in the drilling fluid corresponding to the telemetry signal. Alternatively, the method can comprise a modulation technique that includes amplitude shift keying and phase shift keying and wherein each symbol of the selected symbol set is assigned a pressure pulse having a unique combination of amplitude and phase.

Abstract: A gap sub has electrically-conductive parts held together by electrical insulators which engage in channels formed in the parts. The electrical insulators hold the parts in a spaced-apart electrically-insulated relationship. In some embodiments, the electrical insulators are removable to allow separation of the parts. An insulating oil or other fluid may fill the gap.

Abstract: The present disclosure is directed at methods, systems, and techniques for managing batteries for use in a downhole drilling application. The system includes a power bus, pairs of battery terminals for connecting to batteries, switching circuitry that connects and disconnects the batteries to the power bus, data collection circuitry that obtains battery parameters obtained during system operation, and a controller that controls the switching circuitry and receives the battery parameters. A control line connects the controller to the switching circuitry and a data line connects the controller to the data collection circuitry, with the control and data lines being distinct such that control and data signals are not multiplexed with each other.

Abstract: A fluid pressure pulse generating apparatus including a pulser assembly and a fluid pressure pulse generator and methods of using the fluid pressure pulse generating apparatus. The pulser assembly comprises a motor, a sensor for detecting rotation of the motor, a driveshaft rotationally coupled to the motor, and processing and motor control equipment communicative with the motor and the sensor. The fluid pressure pulse generator is coupled with the driveshaft. The sensor provides an indication of the amount of rotation of the motor and this information can be processed by the processing and motor control equipment to determine the position of the driveshaft and to control rotation of the driveshaft based on a predetermined rotational relationship between the driveshaft and the motor.

Abstract: The embodiments described herein generally relate to a fluid pressure pulse generating apparatus with a primary seal assembly, back up seal assembly and pressure compensation device. The pressure compensation device comprises a membrane support and a longitudinally extending membrane system. The membrane support has a longitudinally extending bore therethrough for receiving a driveshaft of the fluid pressure pulse generating apparatus. The longitudinally extending membrane system comprising a longitudinally extending outer membrane sleeve and a longitudinally extending inner membrane sleeve with the inner membrane sleeve positioned inside the outer membrane sleeve. The membrane system is sealed to the membrane support to allow flexing of the membrane system in response to fluid pressure on either an inner longitudinal surface of the membrane system or an outer longitudinal surface of the membrane system and to prevent fluid on the inner longitudinal surface mixing with fluid on the outer longitudinal surface.

Abstract: An assembly for use in subsurface drilling includes a downhole probe supported by a centralizer. The centralizer comprises a tubular member that extends around the downhole probe. A wall of the centralizer is fluted to provide inward contact points that support the downhole probe and outward contact points that bear against a bore wall of a section of drill string. The downhole probe may be supported for substantially its entire length.

Abstract: A method for regulating an electromagnetic (“EM”) telemetry signal sent from downhole to surface includes determining a value of a controlled parameter of the EM telemetry signal, comparing the value of the controlled parameter to a configuration value, and adjusting the value of the controlled parameter in a first direction towards the configuration value while monitoring a feedback parameter of the EM telemetry signal when the value of the controlled parameter and the configuration value differ. The controlled parameter is one of transmission voltage and transmission current, and the feedback parameter is the other of transmission voltage and transmission current.

Abstract: A coupling key for fixedly coupling a driveshaft to a rotating component of a measurement while drilling telemetry apparatus comprises a key body and at least one zero backlash ring. The key body has dimensions selected to fit within a keyhole of a driveshaft and a receptacle of a rotating component, with a gap that is large enough that the key body can be freely inserted into the keyhole and receptacle and small enough that the coupling body can couple the driveshaft to the rotating component in a rotational direction. The least one zero backlash ring extends around the key body and protrudes from surfaces of the key body and into the gap such that an interference fit is established between the coupling key, the keyhole, and the receptacle when the coupling key is coupling the driveshaft and rotating component together.