Agitator sub

Abstract

A hydraulically driven agitator sub includes: a tubular body for connection within a string including a first mandrel and a second mandrel, and a central bore defining a longitudinal axis of the tubular body and creating a flow path permitting a flow of fluids between the two mandrels and through the tubular body, the second mandrel secured, at least partially, within an annular bore of the first mandrel so that the second mandrel is telescopically arranged with and axially moveable within the first mandrel between a telescopically extended position and a compressed position; and a first sealing part and a second sealing part, one of the first and the second sealing part being secured to the first mandrel and the other sealing part being secured to the second mandrel, both sealing parts being within the fluid flow path of the tubular body, the first sealing part and the second sealing part being positioned to come together when the first mandrel and the second mandrel are in the compressed position to form a seal in the fluid path, the seal substantially preventing the flow of fluids through the tubular body

1 . An apparatus comprising: a tubular body for connection within a string including a first mandrel and a second mandrel, and a central bore defining a longitudinal axis of the tubular body and creating a flow path permitting a flow of fluids between the two mandrels and through the tubular body, the second mandrel secured, at least partially, within an annular bore of the first mandrel so that the second mandrel is telescopically arranged with and axially moveable within the first mandrel between a telescopically extended position and a compressed position; and a first sealing part and a second sealing part, one of the first and the second sealing part being secured to the first mandrel and the other sealing part being secured to the second mandrel, both sealing parts being within the fluid flow path of the tubular body, the first sealing part and the second sealing part being positioned to come together when the first mandrel and the second mandrel are in the compressed position to form a seal in the fluid path, the seal substantially preventing the flow of fluids through the tubular body. 
     
     
         2 . The apparatus of  claim 1  further comprising a biasing member acting between the first mandrel and the second mandrel and biasing the first mandrel and the second mandrel toward the compressed position. 
     
     
         3 . The apparatus of  claim 1  further comprising a transmission arrangement between the first mandrel and the second mandrel to transmit torsional forces therebetween. 
     
     
         4 . The apparatus of  claim 1  further comprising a dampener to act between the first mandrel and the second mandrel in the compressed position to mitigate damaging contact between the first sealing part and the second sealing part. 
     
     
         5 . The apparatus of  claim 1  wherein the first sealing part has an aperture therethrough forming a portion of the fluid flow path and the second sealing part includes a profile portion that seats in and plugs the center aperture when the first sealing part and the second sealing part come together to form a seal. 
     
     
         6 . A drill string comprising: a string of tubulars; a drill bit connected at a distal end of the string of tubulars; a drill collar; and a hydraulically driven agitator positioned between the drill bit and the drill collar. 
     
     
         7 . The drill string of  claim 6  wherein the hydraulically driven agitator includes: a tubular body including a first mandrel connected at an upper end directly or indirectly to the drill collar and a second mandrel connected at a lower end directly or indirectly to the drill bit, and a central bore defining a longitudinal axis of the tubular body and creating a flow path permitting a flow of fluids between the two mandrels and through the tubular body, the second mandrel secured, at least partially, within an annular bore of the first mandrel so that the second mandrel is telescopically arranged with and axially moveable within the first mandrel between a telescopically extended position and a compressed position; and a first sealing part and a second sealing part, one of the first and the second sealing part being secured to the first mandrel and the other sealing part being secured to the second mandrel, both sealing parts being within the fluid flow path of the tubular body, the first sealing part and the second sealing part being positioned to come together when the first mandrel and the second mandrel are in the compressed position to form a seal in the fluid path, the seal substantially preventing the flow of fluids through the tubular body. 
     
     
         8 . The drill string of  claim 7  wherein the hydraulically driven agitator further comprises a biasing member acting between the first mandrel and the second mandrel and biasing the first mandrel and the second mandrel toward the compressed position. 
     
     
         9 . The drill string of  claim 7  wherein the hydraulically driven agitator further comprises a transmission arrangement between the first mandrel and the second mandrel to transmit torsional forces therebetween. 
     
     
         10 . The drill string of  claim 7  wherein the hydraulically driven agitator further comprises a dampener to act between the first mandrel and the second mandrel in the compressed position to mitigate damaging contact between the first sealing part and the second sealing part. 
     
     
         11 . The drill string of  claim 7  wherein the first sealing part has an aperture therethrough forming a portion of the fluid flow path and the second sealing part includes a profile portion that seats in and plugs the center aperture when the first sealing part and the second sealing part come together to form a seal. 
     
     
         12 . A method for creating an agitation effect in a wellstring, the method comprising: connecting an apparatus according to  claim 1  in-line with a wellbore string to position the second mandrel and the first mandrel in the compressed position when there is weight on bit in the wellbore string; applying weight on bit to position the first mandrel and the second mandrel in the fully compressed position; pumping fluids through the wellbore string to develop a fluid pressure overcoming the weight on bit holding the first mandrel and the second mandrel in compressed position and driving the first mandrel and the second mandrel apart; allowing the pressure to dissipate such that the first mandrel and the second mandrel return back to the compressed position; and continuing to pump fluids through the wellbore string to create an agitation effect as the first mandrel and the second mandrel continue to be pumped apart and then returned to the compressed position. 
     
     
         13 . The method of  claim 12  further comprising applying torsional forces through the wellbore string and transmitting the torsional forces through the apparatus. 
     
     
         14 . The method of  claim 12  wherein driving the first mandrel and the second mandrel apart includes lifting a drill collar upwardly away from a drill bit.