Method for generating pressure fluctuations in a flowing fluid

Abstract

An anti-plugging oscillating shear valve system for generating pressure fluctuations in a flowing drilling fluid comprising a stationary stator and an oscillating rotor, both with axial flow passages. The rotor oscillates in close proximity to the stator, at least partially blocking the flow through the stator and generating oscillating pressure pulses. The rotor passes through two zero speed positions during each cycle, facilitating rapid changes in signal phase, frequency, and/or amplitude facilitating enhanced data encoding. The rotor is driven by a electric motor disposed in a lubricant filled housing. In one embodiment, the housing to shaft seal is a flexible bellows. In one embodiment, a torsional spring is attached to the motor and the resulting spring mass system is designed to be near resonance at the desired pulse frequency. The torsion spring may be a solid torsion bar or a magnetic spring.

What is claimed is:  
     
         1 . An oscillating shear valve system for generating pressure fluctuations in a flowing drilling fluid, comprising: 
 a tool housing with an upper end and a lower end, said tool housing adapted to be inserted in a bottom hole drilling assembly, said tool housing having an internal bore adapted to support a pulser assembly;    a pulser assembly, comprising; 
 a non-rotating stator disposed in the flowing drilling fluid, said stator having a plurality of flow passages to channel the drilling fluid;  
 a rotor disposed in the flowing drilling fluid proximate the stator, the rotor having a plurality of flow passages matching the plurality of flow passages in the stator;  
 a drive motor adapted to drive the rotor in a rotationally oscillating manner, thereby generating pressure fluctuations in the drilling fluid;  
 an oil filled pulser housing, said housing having an open end and a closed end, the housing adapted for mounting the drive motor and a drive shaft, the drive shaft having a first end and a second end, said first end adapted for attaching to the motor, and said second end adapted for attaching to the rotor, the housing open end adapted to mount a fluid seal for sealing between the housing and the drive shaft; and,  
   an electronics module for controlling the drive motor.    
     
     
         2 . The oscillating shear valve system of  claim 1 , wherein, the fluid seal for environmentally sealing between the housing and the drive shaft is a flexible elastomeric bellows, the flexible elastomeric bellows having a first end and a second end, said first end is adapted to fixedly attach to the drive shaft and said second end is adapted to fixedly attach to the pulser housing, the elastomeric bellows flexing torsionally as the drive shaft rotationally oscillates, said bellows providing pressure equalization to the oil filled housing for the downhole drilling fluid pressure.  
     
     
         3 . The oscillating shear valve system of  claim 2  wherein the tool housing is further adapted to house at least one upper pressure sensor proximate the upper end and at least one lower pressure sensor proximate the lower end;  
     
     
         4 . The oscillating shear valve system of  claim 2  wherein the electronics module comprises circuitry to power and control the motion of the motor, said circuitry including a programmable processor adapted to perform programmed instructions for controlling the motion of the motor;  
     
     
         5 . The oscillating shear valve system of  claim 3  wherein the electronics module comprises circuitry to power and control the motion of the motor, and to power and read the at least one upper pressure sensor and the at least one lower pressure sensor, said circuitry including a programmable processor adapted to perform programmed instructions for controlling the motion of the motor, said processor further adapted to read pressure signals from the at least one upper pressure sensor and the at least one lower pressure sensor, said processor modifying the motor motion, according to programmed instructions, so as to maintain a predetermined pressure differential between the at least one upper pressure sensor and the at least one lower pressure sensor.  
     
     
         6 . The oscillating shear valve system of  claim 5  wherein the programmable processor is adapted, according to programmed instructions, to detect and decode a command pressure pulse signal sent from a surface location, said processor thereby modifying the motion of the motor, according to programmed instructions.  
     
     
         7 . The oscillating shear valve system of  claim 3 , wherein the drive motor is a reversible D.C. motor.  
     
     
         8 . The oscillating shear valve system of  claim 3 , wherein the drive motor is a stepper motor.  
     
     
         9 . An oscillating shear valve system for generating pressure fluctuations in a flowing drilling fluid, comprising: 
 a tool housing with an upper end and a lower end, said tool housing adapted to be inserted in a bottom hole drilling assembly, said tool housing having an internal bore adapted to support a pulser assembly;    a pulser assembly, comprising; 
 a non-rotating stator disposed in the flowing drilling fluid, said stator having a plurality of flow passages to channel the drilling fluid;  
 a rotor disposed in the flowing drilling fluid proximate the stator, the rotor having a plurality of flow passages matching the plurality of flow passages in the stator;  
 a drive motor adapted to drive the rotor in a rotationally oscillating manner, thereby generating pressure fluctuations in the drilling fluid;  
 an oil filled pulser housing, said housing having an open end and a closed end, the housing adapted for mounting the drive motor and a drive shaft, the drive shaft having a first end and a second end, said first end adapted for attaching to the motor, and said second end adapted for attaching to the rotor, the housing open end adapted to mount a fluid seal for sealing between the housing and the drive shaft;  
 a torsional spring with a first end and a second end, the first end of the torsional spring adapted to attach to the second end of the motor drive shaft, and the second end of the torsional spring adapted to be anchored to the pulser housing; and,  
   an electronics module for controlling the drive motor.    
     
     
         10 . The oscillating shear valve system of  claim 9 , wherein, the fluid seal for sealing between the housing and the drive shaft is a flexible elastomeric bellows, the flexible elastomeric bellows having a first end and a second end, said first end is adapted to fixedly attach to the drive shaft and said second end is adapted to fixedly attach to the pulser housing, the elastomeric bellows flexing torsionally as the drive shaft rotationally oscillates, said bellows providing pressure equalization to the oil filled housing for the downhole drilling fluid pressure  
     
     
         11 . The oscillating shear valve system of  claim 10 , wherein the tool housing is further adapted to house at least one upper pressure sensor proximate the upper end and at least one lower pressure sensor proximate the lower end;  
     
     
         12 . The oscillating shear valve system of  claim 10 , wherein the electronics module comprises circuitry to power and control the motion of the motor, said circuitry including a programmable processor adapted to perform programmed instructions for controlling the motion of the motor;  
     
     
         13 . The oscillating shear valve system of  claim 11 , wherein the electronics module comprises circuitry to power and control the motion of the motor, and to power and read the at least one upper pressure sensor and the at least one lower pressure sensor, said circuitry including a programmable processor adapted to perform programmed instructions for controlling the motion of the motor, said processor further adapted to read pressure signals from the at least one upper pressure sensor and the at least one lower pressure sensor, said processor modifying the motor motion, according to programmed instructions, so as to maintain a predetermined pressure differential between the at least one upper pressure sensor and the at least one lower pressure sensor.  
     
     
         14 . The oscillating shear valve system of  claim 13 , wherein the programmable processor is adapted, according to programmed instructions, to detect and decode a command pressure pulse signal sent from a surface location, said processor thereby modifying the motion of the motor, according to programmed instructions.  
     
     
         15 . The oscillating shear valve system of  claim 10 , wherein the torsion spring has a predetermined spring constant such that the torsion spring combined with the rotating masses comprising the motor drive shaft, the drive shaft, and the rotor comprise a torsional spring-mass system whose torsional resonant frequency is related to the operating pulse frequency.  
     
     
         16 . The oscillating shear valve system of  claim 15 , wherein the torsion spring is a solid rod.  
     
     
         17 . The oscillating shear valve system of  claim 15 , wherein the torsion spring comprises: 
 an outer magnet carrier adapted to be rotationally anchored to the pulser housing and adapted to move axially within the pulser housing, said outer magnet carrier having a plurality of permanent bar magnets mounted equally spaced around an inner diameter of the outer magnet carrier, said magnets mounted with alternating magnetic poles normal to the inner diameter of the outer magnet carrier, and,    an inner magnet carrier adapted to attach to the second end of the motor drive shaft, said inner magnet carrier having a plurality of permanent bar magnets mounted equally spaced around an outer diameter of the inner magnet carrier, said magnets mounted with alternating magnetic poles normal to the outer diameter of the inner magnet carrier.    
     
     
         18 . The oscillating shear valve system of  claim 10 , wherein the drive motor is a reversible D.C. motor.  
     
     
         19 . The oscillating shear valve system of  claim 10 , wherein the drive motor is a stepper motor.  
     
     
         20 . A method for generating a fast transition in a mud pulse telemetry scheme utilizing a phase shift key encoding (PSK) scheme, comprising; 
 utilizing an oscillating shear valve to generate pressure pulses, said oscillating shear valve comprising a non-rotating stator; an oscillating rotor, said rotor adapted to rotate in a first direction and a second direction, where said second direction is opposite said first direction; an electric motor for driving the rotor; and an electronics module to control the motor to move in a periodic oscillatory motion such that the rotor transitions through a zero speed each time the rotor direction is reversed, said electronics module comprising circuitry to enable encoding a date stream using PSK;    driving the rotor with a first predetermined signal phase relationship,    changing the drive signal according to the PSK scheme at a predetermined rotor speed, and    attaining a second predetermined phase relationship in no more than one oscillatory period.    
     
     
         21 . The method of  claim 20  wherein the predetermined rotor speed for changing the drive signal is a zero speed transition.  
     
     
         22 . A method for generating a fast transition in a mud pulse telemetry scheme utilizing a frequency shift key encoding (FSK) scheme, comprising; 
 utilizing an oscillating shear valve to generate pressure pulses, said oscillating shear valve comprising a non-rotating stator; an oscillating rotor, said rotor adapted to rotate in a first direction and a second direction, where said second direction is opposite said first direction; an electric motor for driving the rotor; and an electronics module to control the motor to move in a periodic oscillatory motion such that the rotor transitions through a zero speed each time the rotor direction is reversed, said electronics module comprising circuitry to enable encoding a date stream using FSK;    driving the rotor at a first predetermined frequency,    changing the drive signal according to the FSK scheme at a predetermined rotor speed, and    attaining a second predetermined frequency in no more than one oscillatory period.    
     
     
         23 . The method of  claim 22  wherein the predetermined rotor speed for changing the drive signal is a zero speed transition.  
     
     
         24 . A method for generating a fast transition in a mud pulse telemetry scheme utilizing an amplitude shift key encoding (ASK) scheme, comprising; 
 utilizing an oscillating shear valve to generate pressure pulses, said oscillating shear valve comprising a non-rotating stator; an oscillating rotor, said rotor adapted to rotate in a first direction and a second direction, where said second direction is opposite said first direction; an electric motor for driving the rotor;    and an electronics module to control the motor to move in a periodic oscillatory motion such that the rotor transitions through a zero speed each time the rotor direction is reversed, said electronics module comprising circuitry to enable encoding a date stream using ASK;    driving the rotor in an oscillatory periodic motion through a first predetermined rotational angle, thereby generating a first pulse amplitude;    changing the drive signal according to the ASK scheme at a predetermined rotor speed, and    driving the rotor in an oscillatory periodic motion through a second predetermined rotational angle, attaining a second pulse amplitude in no more than one oscillatory period.    
     
     
         25 . The method of  claim 24  wherein the predetermined rotor speed for changing the drive signal is a maximum speed.  
     
     
         26 . A method for generating an increased data rate in a mud pulse telemetry scheme by combining an amplitude shift key encoding (ASK) scheme and a frequency shift key encoding scheme (FSK), comprising; 
 utilizing an oscillating shear valve to generate pressure pulses, said oscillating shear valve comprising a non-rotating stator; an oscillating rotor, said rotor adapted to rotate in a first direction and a second direction, where said second direction is opposite said first direction; an electric motor for driving the rotor; and an electronics module to control the motor to move in a periodic oscillatory motion such that the rotor transitions through a zero speed each time the rotor direction is reversed, said electronics module comprising circuitry to enable encoding a date stream using a combination of ASK and FSK;    driving the rotor in an oscillatory periodic motion through a first predetermined rotational angle at a first frequency, thereby generating a first pulse amplitude at a first frequency;    changing the drive signal according to the ASK and FSK schemes at a predetermined rotor speed, and    driving the rotor in an oscillatory periodic motion through a second predetermined rotational angle at a second predetermined frequency, thereby attaining a second pulse amplitude at a second frequency in no more than one oscillatory period.    
     
     
         27 . A method for generating an increased data rate in a mud pulse telemetry scheme by combining an amplitude shift key encoding (ASK) scheme and a phase shift key encoding scheme (PSK), comprising; 
 utilizing an oscillating shear valve to generate pressure pulses, said oscillating shear valve comprising a non-rotating stator; an oscillating rotor, said rotor adapted to rotate in a first direction and a second direction, where said second direction is opposite said first direction; an electric motor for driving the rotor; and an electronics module to control the motor to move in a periodic oscillatory motion such that the rotor transitions through a zero speed each time the rotor direction is reversed, said electronics module comprising circuitry to enable encoding a date stream using a combination of ASK and PSK;    driving the rotor in an oscillatory periodic motion through a first predetermined rotational angle at a first phase angle, thereby generating a first pulse amplitude at a first phase;    changing the drive signal according to the ASK and PSK schemes at a predetermined rotor speed, and,    driving the rotor in an oscillatory periodic motion through a second rotational angle at a second predetermined phase angle, thereby attaining a second pulse amplitude at a second phase angle in no more than one oscillatory period.    
     
     
         28 . A method for preventing jamming of a mud pulse valve by a foreign body in a fluid stream, comprising utilizing an oscillating shear valve to generate pressure pulses, said oscillating shear valve comprising a non-rotating stator; an oscillating rotor, said rotor adapted to rotate in a first direction and a second direction, where said second direction is opposite said first direction whereby a foreign body is washed out of a flow passage by such oscillating motion.