Downhole assembly

Abstract

A piezo electric control system for use in a downhole assembly which is inserted into a borehole comprising an articulated mandrel, a passive and an active damping mechanism operating on said mandrel for exercising control over torsional stick-slip in which said piezo electric system exercises control.

1 . A downhole assembly comprising piezo electric members configured to output an electrical signal in response to vibration of the assembly and controlling means for controlling an aspect of said downhole assembly, wherein the assembly is configured to provide a proportional control voltage for the controlling means from the magnitude of the electric signal outputted from the piezo electric members. 
     
     
         2 . The assembly according to  claim 1 , wherein said control voltage is provided by the electric signal outputted from the piezo electric members. 
     
     
         3 . The assembly according to  claim 1 , wherein said control means comprises means to damp vibrations in the downhole assembly. 
     
     
         4 . The assembly of  claim 3 , comprising a primary passive damping means and an independently operating secondary, active, damping control means. 
     
     
         5 . The assembly of  claim 1  incorporating piezo electric members which are configured as transducers which are responsive to motion, vibration and compression and which recover waste mechanical energy from the assembly, converting said energy into electrical power, resulting in an electrical signal output responds proportionally to vibration imparted to the assembly during operation. 
     
     
         6 . The assembly of  claim 1  where the piezo electric members comprise piezo electric fibres. 
     
     
         7 . The assembly of  claim 1  configured to harvest electrical energy from the piezo electric members and where said output energy is used as means to measure vibration within distal elements of the downhole assembly. 
     
     
         8 . The assembly of  claim 4  configured to harvest electrical energy from the piezo electric members to provide a proportional control voltage from an electric signal outputted from the piezo electric members for controlling an aspect of the active damping mechanism. 
     
     
         9 . The assembly of  claim 1  wherein the piezo electric members are located in proximity to the distal end of the downhole assembly, 
     
     
         10 . The assembly of  claim 1 , wherein the piezo electric members are embedded in an elastomeric matrix. 
     
     
         11 . A method for harvesting vibration energy from a piezo electric control system for electrical control during a drilling operation, which method comprises use of a downhole assembly according to  claim 1 . 
     
     
         12 . The method of  claim 11 , wherein the downhole assembly comprises a primary passive closed cell elastomeric damping means and an independently operating secondary, active, damping means, a lower assembly and an upper assembly, incorporating piezo electric members configured within a lower sub-assembly, to output an electrical signal which is proportional in response to vibration imparted to the lower assembly and secondary piezo electric members configured within an upper sub-assembly to output an electrical signal response which is proportional to the vibration imparted to the upper assembly. 
     
     
         13 . The method of  claim 12 , wherein a comparison is made between said output electrical signal generated within the lower sub assembly and said output electrical signal generated within the upper sub assembly. 
     
     
         14 . The method of  claim 12 , wherein active damping is applied which is proportional to the differential between the electrical response of the piezo electric member in the lower sub assembly and the electrical response of the piezo-electric member in the upper sub assembly. 
     
     
         15 . The method of  claim 11 , incorporating piezo electric fibres into the downhole assembly for the purpose of generating a proportional electrical output in response to the magnitude of vibration imparted to the assembly. 
     
     
         16 . The method of  claim 15 , wherein said electrical output from the piezo electric fibres is a signal. 
     
     
         17 . The method of  claim 15 , wherein said electrical output from the piezo electric fibres is a control voltage. 
     
     
         18 . The method of  claim 15 , wherein said electrical output is used instantly. 
     
     
         19 . The method of  claim 15 , wherein said electrical output is stored for later usage. 
     
     
         20 . The method of  claim 15 , wherein said electrical output is used to control viscosity of magneto-rheological fluids. 
     
     
         21 . The method of  claim 15 , wherein said electrical output is used to control at least one hydraulic damping valve mechanism. 
     
     
         22 . The method of  claim 15 , where said magnitude of vibration can be segregated into components in order to better comprehend motion of the drilling assembly. 
     
     
         23 . The method of  claim 12 , wherein said damping is continuous. 
     
     
         24 . The method of  claim 12 , wherein intermittent or sporadic active damping is applied.