Near-field sensitivity of formation and cement porosity measurements with radial resolution in a borehole

Abstract

A neutron porosity tool having an electronic neutron generator arrangement and a control mechanism used to provide voltage and pulses to an electronic neutron tube is provided, the neutron generator arrangement including: at least one vacuum tube; at least one ion target; at least one radio-frequency cavity; at least one high-voltage generator; at least two neutron detectors; at least one pulser circuit; and at least one control circuit. A method of controlling a neutron porosity tool having an electronic neutron generator arrangement and a control mechanism that provides voltage and pulses to an electronic neutron tube, the method including at least: controlling a bipolar neutron tube to produce two distinct neutron reactions; using a control circuit to modify the output of a pulser circuit; and using a plurality of neutron detectors to determine formation response offsets.

1 . A neutron porosity tool having an electronic neutron generator arrangement and a control mechanism used to provide voltage and pulses to an electronic neutron tube so that the output of two neutron reaction planes from collocated target planes in a wellbore environment, said neutron generator arrangement comprising:
 at least one vacuum tube;   at least one ion target;   at least one radio-frequency cavity;   at least one high-voltage generator;   at least two neutron detectors;   at least one puller circuit; and   at least one control circuit.   
     
     
         2 . The neutron generator arrangement of  claim 1 , wherein the arrangement is configured as to provide two differing ion accelerating voltages by two high voltage generators, such that deuterium-deuterium and deuterium-tritium reactions may be generated within the same reactants plane. 
     
     
         3 . The neutron generator arrangement of  claim 1 , wherein the arrangement is configured as to provide the same ion accelerating voltages by two high voltage generators, such that deuterium-deuterium reactions are generated on both sides of the target within the same reactants plane. 
     
     
         4 . The neutron generator arrangement of  claim 1 , wherein the arrangement is configured as to provide the same ion accelerating voltages by two high voltage generators, such that deuterium-tritium reactions are generated on both sides of the target within the same reactants plane. 
     
     
         5 . The neutron generator arrangement of  claim 1 , wherein the arrangement is configured as to provide two cathode sources and two co-located targets, such that deuterium-deuterium and deuterium-tritium reactions are generated within the same reactants plane. 
     
     
         6 . The neutron generator arrangement of  claim 1 , wherein two high voltage generators are used to provide differing acceleration voltages on either side of the target, such that deuterium-deuterium and deuterium-tritium reactions are generated within the same reactants plane. 
     
     
         7 . The neutron generator arrangement of  claim 1 , wherein the pulser circuits are configured to provide pulses to either side of the target concurrently so that deuterium-deuterium and deuterium-tritium reaction outputs are distinct and individual. 
     
     
         8 . The neutron generator arrangement of  claim 1 , wherein the pulser circuits are configured to provide pulses to either side of the target alternately, such that deuterium-deuterium and deuterium-tritium reaction outputs are distinct and individual. 
     
     
         9 . The tool of  claim 1 , where the detectors comprise helium-3 gas. 
     
     
         10 . The tool of  claim 1 , where the detectors comprise Lithium-6 glass. 
     
     
         11 . A method of controlling a neutron porosity tool having an electronic neutron generator arrangement and a control mechanism that provides voltage and pulses to an electronic neutron tube thereby enabling the production of two distinct neutron energies to provide radial discrimination of porosity, said method comprising:
 controlling a bipolar neutron tube to produce two distinct neutron reactions;   using a control circuit to modify the output of a pulser circuit; and   using a plurality of neutron detectors to determine formation response offsets.   
     
     
         12 . The method of  claim 11 , further comprising configuring the neutron generator arrangement to provide two differing ion accelerating voltages by two high voltage generators such that deuterium-deuterium and deuterium-tritium reactions may be generated within the same reactants plane. 
     
     
         13 . The method of  claim 11 , further comprising configuring the arrangement is to provide two cathode sources and two co-located targets such that deuterium-deuterium and deuterium-tritium reactions are generated within the same reactants plane. 
     
     
         14 . The method of  claim 11 , further comprising controlling two high voltage generators to provide differing acceleration voltages on either side of the target, such that deuterium-deuterium and deuterium-tritium reactions are generated within the same reactants plane. 
     
     
         15 . The method of  claim 11 , further comprising controlling the pulser circuits so as to provide pulses to either side of the target concurrently, such that deuterium-deuterium and deuterium-tritium reaction outputs are distinct and individual. 
     
     
         16 . The method of  claim 11 , further comprising configuring the pulser circuits so as to provide pulses to either side of the target alternately, such that deuterium-deuterium and deuterium-tritium reaction outputs are distinct and individual.