System, method and apparatus for drilling agitator

Abstract

A drilling agitator tool, system and method facilitates axial movement of a drill string in a well. The tool has a valve assembly that provides pulses of fluid pressure in the drill string. A valve control assembly controls a frequency and pressure amplitude of the pulses induced by the valve assembly. The valve control assembly monitors real-time pressure and vibration levels of the drill string. An agitator assembly reciprocates in response to the pulses of fluid pressure to provide axial movement of the drill string in the well.

What is claimed is: 
     
         1 . A drilling agitator for a drill string in a well, comprising:
 a valve assembly that provides pulses of fluid pressure in the drill string;   a valve control assembly that controls a frequency and pressure amplitude of the pulses induced by the valve assembly, and the valve control assembly monitors real-time pressure and vibration levels of the drill string; and   an agitator assembly that reciprocates in response to the pulses of fluid pressure to provide axial movement of the drill string in the well.   
     
     
         2 . A drilling agitator according to  claim 1 , wherein the valve assembly contains a servo shaft that is coupled to a ramp to axially move a servo tip between open and closed positions, the ramp being moved axially in one direction in response to rotation of an impeller by a motor, and in an opposite direction in response to a spring force. 
     
     
         3 . A drilling agitator according to  claim 2 , wherein control of the motor controls the frequency and duration of the axial movement of the servo tip, and control is provided by a circuit to control a rotational speed of the impeller, and cyclic movement of the signal poppet in response thereto. 
     
     
         4 . A drilling agitator according to  claim 3 , wherein the circuit further comprises at least one accelerometer to monitor axial acceleration of the drill string, wherein a decrease in rotational speed induces a slower cycle in pressure but increases pressure amplitude, which causes an increase in axial acceleration and movement of the agitator assembly and the drill string. 
     
     
         5 . A drilling agitator according to  claim 1 , wherein the agitator assembly comprises a mandrel coupled to a housing, a spring for biasing the mandrel out of the housing, a disc spring for drawing the mandrel into the housing, a compensation piston coupled to the mandrel for circulating fluid thereto, the mandrel being responsive to the fluid pressure pulses to oscillate relative to the housing and axially move the drill string. 
     
     
         6 . A drilling agitator according to  claim 1 , wherein the agitator assembly comprises a plurality of agitator assemblies and the valve assembly is located axially between at least two of the agitator assemblies. 
     
     
         7 . A system for facilitating axial movement in a well, comprising:
 a drill string having a drill bit and a drilling agitator; the drilling agitator comprising:   a valve assembly that provides pulses of fluid pressure increase in the drill string above the drill bit;   a valve control assembly that controls a frequency and pressure amplitude of the pulses induced by the valve assembly, and the valve control assembly monitors real-time pressure and vibration levels of the drill string; and   an agitator assembly that reciprocates in response to the pulses of fluid pressure to provide axial movement of the drill string in the well.   
     
     
         8 . A system according to  claim 7 , wherein the valve assembly comprises a signal poppet that is axially movable within a valve body relative to an orifice, the signal poppet having an extended position that restricts but does not prevent fluid flow through the orifice, and a retracted position that permits the free flow of fluid through the orifice. 
     
     
         9 . A system according to  claim 8 , wherein the signal poppet is spring-biased to the extended position, fluid flows between an exterior of the signal poppet and an interior of the orifice, and the signal poppet has a bore through which fluid flows. 
     
     
         10 . A system according to  claim 9 , wherein the valve assembly further comprises an upper inner passage that extends axially through a valve seat that is in fluid communication with the bore of the signal poppet, and a servo valve assembly that opens and closes the valve seat to regulate fluid flow therethrough to actuate the signal poppet. 
     
     
         11 . A system according to  claim 10 , wherein the servo valve assembly comprises a servo shaft extending through an evacuation sub, the servo shaft having a servo tip with an closed position for engaging the valve seat to block the fluid flow to the upper inner passage, and an open position wherein the servo tip is removed from the valve seat to permit fluid flow to the upper inner passage. 
     
     
         12 . A system according to  claim 11 , wherein the closed position actuates the signal poppet to the retracted position, and the open position actuates the signal poppet to the extended position and thereby form a pressure pulse. 
     
     
         13 . A system according to  claim 11 , wherein the valve seat is located in a valve chamber having an opening for permitting fluid to enter the valve chamber from an annulus between the servo valve assembly and a housing thereof. 
     
     
         14 . A system according to  claim 11 , wherein the servo shaft is coupled to a ramp to axially move the servo tip between the open and closed positions, the ramp being moved axially in one direction in response to rotation of an impeller by a motor, and in an opposite direction in response to a spring force. 
     
     
         15 . A system according to  claim 14 , wherein control of the motor controls the frequency and duration of the axial movement of the servo tip, and control is provided by a circuit to control a rotational speed of the impeller, and cyclic movement of the signal poppet in response thereto. 
     
     
         16 . A system according to  claim 15 , wherein the circuit further comprises at least one accelerometer to monitor axial acceleration of the drill string, wherein a decrease in rotational speed induces a slower cycle in pressure but increases pressure amplitude, which causes an increase in axial acceleration and movement of the agitator assembly and the drill string. 
     
     
         17 . A system according to  claim 7 , wherein the agitator assembly comprises a mandrel coupled to a housing, a spring for biasing the mandrel out of the housing, a disc spring for drawing the mandrel into the housing, a compensation piston coupled to the mandrel for circulating fluid thereto, the mandrel being responsive to the fluid pressure pulses to oscillate relative to the housing and axially move the drill string. 
     
     
         18 . A system according to  claim 7 , wherein the agitator assembly comprises a plurality of agitator assemblies and the valve assembly is located axially between at least two of the agitator assemblies. 
     
     
         19 . A method of facilitating axial movement of a drill string while drilling a well, comprising:
 operating a drill string in a well in a dynamic mode;   detecting an axial acceleration of the drill string and, if the axial acceleration is insufficient, pulsing fluid pressure in the drill string between a normal circulation pressure and an elevated pressure, and, if vibration is excessive, pulsing fluid pressure in the drill string between the normal condition and a lower pressure; and   reciprocating an agitator in response to the pulsing fluid pressure to facilitate axial movement of the drill string in the well.   
     
     
         20 . A method according to  claim 19 , wherein the dynamic mode is drilling with a drill bit or steering the drill bit. 
     
     
         21 . A method according to  claim 19 , further comprising:
 determining a desired vibration level of the drill string by stepping through a series of preprogrammed increments of frequency and pressure amplitude for the pulsing fluid;   operating the drill sting at the desired vibration level;   monitoring the axial acceleration of the drill string; and   adjusting the vibration level to improve the axial acceleration of the drill string.   
     
     
         22 . A method according to  claim 19 , wherein the frequency is about 5 to 40 Hz, and pressure amplitude of the valve assembly is controlled by an electronic circuit that monitors real-time pressure and vibration levels down hole. 
     
     
         23 . A method according to  claim 19 , wherein the frequency is adjusted by about 1 Hz when the pressure or vibration level is above or below an acceptable range.