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A mud pulser controlled by a field applied to an electroactive fluid. The electroactive fluid is employed to act as a rapid-response brake to slow or interrupt the rotation of a mud motor or mud siren, thus creating pressure pulses in a circulating fluid. In certain embodiments, the electroactive fl

A mud pulser controlled by a field applied to an electroactive fluid. The electroactive fluid is employed to act as a rapid-response brake to slow or interrupt the rotation of a mud motor or mud siren, thus creating pressure pulses in a circulating fluid. In certain embodiments, the electroactive fluid is used as a direct brake acting on a shaft rotating in a volume of electroactive fluid where the shaft is coupled to the mud motor or siren. The application of a field to the electroactive fluid impedes the rotation of the shaft, thus slowing the mud motor and creating a pressure pulse in the circulating fluid. In another embodiment, a Moineau pump circulating an electroactive fluid is coupled to the mud motor. The application of a field to the electroactive fluid slows the rotation of the pump, thus slowing the mud motor and creating a pressure pulse in the circulating fluid.

대표청구항 ▼

What is claimed is: 1. A pressure pulser comprising: a first rotatable body in fluid communication with a flowing fluid; a second body coupled to said first body and at least partially disposed within an electroactive fluid, wherein said electroactive fluid is isolated from said flowing fluid; and

What is claimed is: 1. A pressure pulser comprising: a first rotatable body in fluid communication with a flowing fluid; a second body coupled to said first body and at least partially disposed within an electroactive fluid, wherein said electroactive fluid is isolated from said flowing fluid; and a means for applying a field to the electroactive fluid. 2. The pulser of claim 1 wherein said first body is a mud motor. 3. The pulser of claim 1 wherein said second body comprises a shaft and said means for applying a field includes an electromagnetic coil. 4. The pulser of claim 1 wherein said second body is pump rotor circulating the electroactive fluid through a flowline. 5. The pulser of claim 4 further comprising a field-generating valve disposed on the flowline, wherein said valve has a blocked position where a field is applied to the flowline. 6. The pulser of claim 4 wherein the pulser is integrated into a drill string. 7. A method for generating a pressure pulse comprising: disposing a first rotatable body in flowing fluid; coupling the first body to a second body disposed in an electroactive fluid, wherein said electroactive fluid is isolated from said flowing fluid; applying a field to the electroactive fluid. 8. The method of claim 7 wherein the field is applied by applying a current to an electromagnetic coil. 9. The method of claim 7 wherein the field is applied by a magnetic circuit. 10. The method of claim 7 wherein said first body is a mud motor. 11. The method of claim 7 wherein said second body comprises a shaft and an electromagnetic coil. 12. The method of claim 7 wherein said second body is pump rotor circulating the electroactive fluid through a flowline. 13. The method of claim 12 further comprising a field-generating valve disposed on the flowline, wherein said valve has a blocked position where a field is applied to the flowline. 14. The method of claim 7 wherein the first and second bodies are integrated into a drill string. 15. An apparatus for generating a pressure pulse in a column of circulating fluid, the apparatus comprising: a first rotating member disposed in the column of circulating fluid; a chamber containing an electroactive fluid isolated from the circulating fluid; a second rotating member attached to said first rotating member and at least partially contained within said chamber of electroactive fluid; a magnet proximate to said chamber of electroactive fluid and switchable between first and second states so as to apply a field to the electroactive fluid in the first state and not apply a field to the electroactive fluid in the second state. 16. An apparatus for generating pressure pulses in a column of circulating fluid, the apparatus comprising: a housing adapted for communicating the circulating fluid therethrough; a first body in said housing and adapted for rotation in the circulating fluid; a chamber in said housing and enclosing an electroactive fluid; wherein said chamber is isolated from the circulating fluid; a second body in said housing and connected to said first body; wherein said second body is at least partially disposed within said chamber and has an outer surface in contact with said electroactive fluid; and a magnet switchable between a first state applying a field to the electroactive fluid and a second state not applying a field to the electroactive fluid. 17. The apparatus of claim 16 wherein said first body is a mud motor. 18. The apparatus of claim 17 wherein said second body is a shaft. 19. The apparatus of claim 17 wherein said second body is a Moineau pump. 20. The apparatus of claim 16 wherein said magnet is an electromagnet. 21. The apparatus of claim 20 wherein said first body is a mud motor and said second body is a shaft. 22. The apparatus of claim 16 wherein said magnet is a permanent magnet. 23. The apparatus of claim 16 wherein said first body is a rotor and said second body is a shaft. 24. The apparatus of claim 23 wherein said second body extends through said chamber and is connected to a motor.