A telemetry system includes a downhole device configured to generate modulated pressure pulses in drilling fluid within a drill string, first and second transducers configured provide first and second telemetry signals, respectively, responsive to pressure variations in the drilling fluid, and a telemetry computer coupled to the transducers. The telemetry computer includes a processor and a memory coupled to the processor. The memory contains instructions that, when executed by the processor, cause the telemetry computer to be configured to transform the first and second telemetry signals to a time-frequency domain representation to provide first and second time-frequency telemetry signals, respectively; and apply an unmixing filter to the first and second time-frequency telemetry signals to provide an enhanced signal in the time-frequency domain. The enhanced signal has a source signal component separated from a noise component, and the first and second telemetry signals are mixed source-noise signals.

A method of determining the condition of a drill string includes receiving, by a processing device and from one or more sensors coupled to a portion of a drill string at or near a surface of a wellbore, noise information. The noise information represents drilling vibrations of the drill string during drilling of the wellbore. The method also includes determining, by the processing device based on the noise information, multiple vibration modes of the drill string. The method also includes comparing, by the processing device, the vibration modes to at least one vibration mode threshold. The method also includes determining, by the processing device based on the comparison of the vibration modes to the at least one vibration mode threshold, a condition of the drill string.

A method of determining the condition of a drill string includes receiving, by a processing device and from one or more sensors coupled to a portion of a drill string at or near a surface of a wellbore, noise information. The noise information represents drilling vibrations of the drill string during drilling of the wellbore. The method also includes determining, by the processing device based on the noise information, multiple vibration modes of the drill string. The method also includes comparing, by the processing device, the vibration modes to at least one vibration mode threshold. The method also includes determining, by the processing device based on the comparison of the vibration modes to the at least one vibration mode threshold, a condition of the drill string.

A system for fluidic siren based telemetry is provided. The system includes a non-rotating restrictor and a rotating restrictor positioned relative to the non-rotating restrictor that is configured to control a flow passage to the non-rotating restrictor. The system includes a turbine coupled to the rotating restrictor and configured to rotate in response to fluid flow along a flow path. The system also includes a generator coupled to the turbine and a controller device electrically coupled to the generator. The controller device is configured to provide one or more encoded signals to the generator to adjust a rotational velocity of the rotating restrictor and causing the rotating restrictor to create different acoustic signatures through the flow passage for wireless communication of a telemetry signal to a surface based on the adjusted rotational velocity of the rotating restrictor.

A method and system for downhole pulse generation determines an optimal frequency and, in some embodiments, amplitude of axial pressure pulses to maximize the rate of penetration. Specifically, one or more sensors may be disposed on or near an axial oscillation tool that provides near real-time raw sensor data relating to speed, velocity, and acceleration of the tool. With this sensor data, an optimal set of parameters, namely an optimal frequency and, in some embodiments, amplitude may be determined based on the hydraulic conditions and frictional forces of the actual drilling environment. An optimizing control system may directly communicate these parameters to the axial oscillation tool or pass the parameters to an axial oscillation tool control system that controls the operation of the tool. Advantageously, frictional forces may be substantially reduced, the rate of penetration may be substantially enhanced, and power consumption may be intelligently managed.

A mud pulser for generating pulses in a fluid flow in a wellbore. The mud pulser has a valve housing having an uphole opening for receiving fluid flow, and a piston valve situated in a piston chamber is longitudinally moveable between an open and closed position by closing and opening a pilot port downhole of the uphole opening and in fluid communication with the piston chamber. A first channel extends in the sidewall of the valve housing and fluidly connects the uphole opening and the pilot port. One or more fluid egress ports are in communication with the piston chamber. A metering orifice may be inserted in said one or more fluid egress ports for first channel. Opening and closing the downhole pilot port moves the piston valve and thus opens and closes the uphole opening thereby generating pressure pulses in the fluid flow. A downhole valve is further disclosed.

A mud pulser for generating pulses in a fluid flow in a wellbore. The mud pulser has a valve housing having an uphole opening for receiving fluid flow, and a piston valve situated in a piston chamber is longitudinally moveable between an open and closed position by closing and opening a pilot port downhole of the uphole opening and in fluid communication with the piston chamber. A first channel extends in the sidewall of the valve housing and fluidly connects the uphole opening and the pilot port. One or more fluid egress ports are in communication with the piston chamber. A metering orifice may be inserted in said one or more fluid egress ports for first channel. Opening and closing the downhole pilot port moves the piston valve and thus opens and closes the uphole opening thereby generating pressure pulses in the fluid flow. A downhole valve is further disclosed.

A fluid pulse generator can include a fluid motor including a rotor that rotates in response to fluid flow, a variable flow restrictor positioned upstream of the fluid motor and including a restrictor member rotatable relative to a ported member and longitudinally displaceable relative to the rotor. Another fluid pulse generator can include a flex joint or a constant velocity joint connected between the restrictor member and the rotor. In another fluid pulse generator, the variable flow restrictor can include a valve and a fluidic restrictor element, the valve being operable in response to rotation of the rotor, the fluidic restrictor element being configured to generate fluid pulses in response to the fluid flow through a flow path, and the valve being configured to control the fluid flow through another flow path connected in parallel with the first flow path.

A device for generating oscillating signals includes an energy transfer device configured to apply an oscillating signal to a sensitive volume, and a resonant tuning circuit including the energy transfer device. The tuning circuit includes a tuning capacitor configured to cause the tuning circuit to resonate at a selected frequency, and an energy storage device. The transmitting device also includes a controller configured to apply a pulse sequence to the tuning circuit having a series of pulses, the energy storage device configured to retain electrical energy at an end of a first pulse, and discharge the electrical energy to the tuning circuit at an onset of a next pulse of the pulse sequence.

A device for generating oscillating signals includes an energy transfer device configured to apply an oscillating signal to a sensitive volume, and a resonant tuning circuit including the energy transfer device. The tuning circuit includes a tuning capacitor configured to cause the tuning circuit to resonate at a selected frequency, and an energy storage device. The transmitting device also includes a controller configured to apply a pulse sequence to the tuning circuit having a series of pulses, the energy storage device configured to retain electrical energy at an end of a first pulse, and discharge the electrical energy to the tuning circuit at an onset of a next pulse of the pulse sequence.