Nuclear magnetic resonance fluid characterization apparatus and method for using with electric wireline formation testing instruments

Abstract

A method for characterizing a fluid sample withdrawn from an earth formation. The method includes performing nuclear magnetic resonant spin echo measurements on the fluid sample at a nuclear magnetic resonant frequency of carbon-13. Amplitudes of the spin echo measurements are summed. The summed measurements are spectrally analyzed. The fluid is characterized by determining whether aromatic hydrocarbons are present by measuring an amplitude of the spectrally analyzed spin echo measurements at about 130 part per million shift from the carbon-13 frequency. The fluid is also characterized by determining whether aliphatic hydrocarbons are present by measuring an amplitude of the spectrally analyzed spin echo measurements at about 30 parts per million frequency shift.

1. A method for characterizing a fluid sample in a chamber on a wireline instrument, said fluid withdrawn from an earth formation, comprising:
 performing magnetic resonant spin echo measurements on said fluid sample in said chamber at a magnetic resonant frequency of carbon-13;  
 summing amplitudes of said spin echo measurements;  
 spectrally analyzing said summed amplitudes;  
 determining whether aromatic hydrocarbons are present in said fluid sample by measuring an amplitude of said spectrally analyzed summed amplitudes at about 130 parts per million shift from said carbon-13 resonant frequency and determining whether aliphatic hydrocarbons are present in said fluid sample by measuring an amplitude of said spectrally analyzed summed amplitudes at about 30 parts per million frequency shift from said carbon-13 resonant frequency.  
 
     
     
       2. The method as defined in  claim 1  further comprising improving a signal-to-noise ratio of said spin echo measurements by:
 performing spin echo measurements on a first portion of said sample in said chamber during a wait time between sets of said spin echo measurements performed on a second portion of said sample, said first portion substantially unaffected by a radio frequency magnetic field used to make said spin echo measurements on said second portion; and  
 stacking said spin echo measurements made on said first portion and said second portion.  
 
     
     
       3. The method as defined in  claim 1  further comprising measuring a magnitude of a static magnetic field in said chamber used to make said spin echo measurements and superimposing a selectable magnitude magnetic field on said static magnetic field of compensate for temperature induced changes in said magnitude of said static magnetic field. 
     
     
       4. The method as defined in  claim 1  further comprising performing nuclear magnetic resonance spin echo amplitude measurements in said chamber at a resonant frequency of hydrogen nuclei, and determining a relaxation rate of said hydrogen nuclei. 
     
     
       5. An apparatus for characterizing  which characterizes a fluid sample withdrawn from an earth formation, said fluid sample being contained in a chamber on a wireline instrument, comprising:
 a magnet for inducing  which induces a substantially homogeneous static magnetic field in at least a portion of said sample in said chamber;  
 a first antenna for inducing  which induces a radio frequency magnetic field in said at least a portion of said sample in said chamber, said radio frequency magnetic field substantially perpendicular to a magnetization direction of said static magnetic field;  
 circuits coupled to said antenna for performing  which perform nuclear magnetic resonance spin echo measurements at a nuclear magnetic resonant frequency of carbon-13, said circuits including means for stacking said spin echo measurements over a measurement sequence; and  
 a spectral analyzer for measuring  which measures amplitudes of components of said spin echo measurements at frequency shifts of 30 and 130 parts per million from said resonant frequency.  
 
     
     
       6. The apparatus as defined in  claim 5  further comprising:
 at least one additional antenna switchably coupled to said circuits for performing  which perform said nuclear magnetic resonance measurements, so that spin echo measurements can be performed during a wait time between measurements sequences performed using said first antenna on a portion of said fluid sample substantially unaffected by radio frequency magnetic fields radiated by said first antenna; and  
 circuits for stacking  which stack measurements made by said first antenna and said at least one additional antenna.  
 
     
     
       7. The apparatus as defined in  claim 5  further comprising:
 a sensor for measuring  which measures a magnitude of said homogeneous static magnetic field induced by said magnets in said fluid sample in said chamber;  
 shim coils located proximal to said fluid sample, said shim coils inducing a selectable magnitude magnetic field on said fluid sample superimposed on said static magnetic field; and  
 circuits for imparting  which impart a direct current to said shim coils in response to an output of said sensor, said direct current adjusted by said circuits to maintain a substantially constant magnetic field amplitude in said fluid sample.  
 
     
     
       8. The apparatus as defined in  claim 5  further comprising circuits selectively coupled to said antenna for performing  which perform nuclear magnetic resonance spin echo measurements at a nuclear magnetic resonant frequency of hydrogen nuclei. 
     
     
       9. An apparatus for characterizing  which characterizes a fluid sample withdrawn from an earth formation, comprising:
 a probe for selective hydraulic engagement with  on a wireline instrument which selectively engages said earth formation using a hydraulic arrangement;  
 a pump coupled to said probe for  which selectively withdrawing  withdraws said fluid sample from said formation; and  
 a nuclear magnetic resonance sensor in said wireline instrument in hydraulic communication with said pump and said probe, said sensor comprising a magnet for inducing  which induces a substantially homogeneous static magnetic field in a chamber including at least a portion of said sample, a first antenna for inducing  which induces a radio frequency magnetic field in said at least a portion of said sample, said radio frequency magnetic field substantially perpendicular to a magnetization direction of said static magnetic field, circuits coupled to said antenna for performing  which perform nuclear magnetic resonance spin echo measurements at a nuclear magnetic resonant frequency of carbon-13, said circuits including means for  enabling stacking said spin echo measurements over a measurement sequence, and a spectral analyzer for measuring amplitudes of components of said spin echo measurements at frequency shifts of 30 and 130 parts per million from said resonant frequency.  
 
     
     
       10. The apparatus as defined in  claim 9  further comprising:
 at least one additional antenna switchably coupled to said circuits for performing  which perform said nuclear magnetic resonance measurements, so that spin echo measurements can be performed during a wait time between measurements sequences performed using said first antenna on a portion of said fluid sample substantially unaffected by radio frequency magnetic fields radiated by said first antenna; and  
 circuits for stacking  which stack measurements made by said first antenna and said at least one additional antenna.  
 
     
     
       11. The apparatus as defined in  claim 9  further comprising:
 a sensor for measuring  which measures a magnitude of said homogeneous static magnetic field induced by said magnets in said fluid sample in said chamber;  
 shim coils located proximal to said fluid sample, wherein said shim coils for inducing  induce a selectable magnitude magnetic field on said fluid sample superimposed on said static magnetic field; and  
 circuits for imparting a direct current to said shim coils in response to an output of said sensor, said direct current adjusted by said circuits to maintain a substantially constant magnetic field amplitude in said fluid sample in said chamber.  
 
     
     
       12. The apparatus as defined in  claim 9  further comprising circuits selectively coupled to said antenna for performing  which perform nuclear magnetic resonance spin echo measurements at a nuclear magnetic resonant frequency of hydrogen nuclei. 
     
     
       13. A method for characterizing a fluid sample withdrawn from an earth formation, comprising:
 placing a probe in hydraulic communication with said earth formation, said probe forming part of an electric wireline formation testing instrument;  
 withdrawing fluid by operating a pump in selective hydraulic communication with said probe;  
 conducting said fluid into a sample chamber disposed in said instrument for performing nuclear magnetic resonance measurements on said fluid therein, said measurements comprising:
 performing magnetic resonant spin echo measurements on said fluid sample in said chamber at a nuclear magnetic resonant frequency of carbon-13, summing amplitudes of said spin echo measurements, spectrally analyzing said summed amplitudes, and determining whether aromatic hydrocarbons are present in said fluid sample by measuring an amplitude of said spectrally analyzed summed amplitudes at about 130 part per million shift from said carbon-13 frequency; and  
 determining whether aliphatic hydrocarbons are present in said fluid sample by measuring an amplitude of said spectrally analyzed summed amplitudes at about 30 parts per million frequency shift.  
 
 
     
     
       14. The method as defined in  claim 13  further comprising improving a signal-to-noise ratio of said spin echo measurements by:
 performing spin echo measurements on a first portion of said sample in said chamber during a wait time between sets of said spin echo measurements performed on a second portion of said sample in said chamber, said first portion substantially unaffected by a radio frequency magnetic field used to make said spin echo measurements on said second portion; and  
 stacking said spin echo measurements made on said first portion and said second portion.  
 
     
     
       15. The method as defined in  claim 13  further comprising measuring a magnitude of a static magnetic field in said chamber used to make said spin echo measurements and superimposing a selectable magnitude magnetic field on said static magnetic field to compensate for temperature induced changes in said magnitude of said static magnetic field. 
     
     
       16. The method as defined in  claim 13  further comprising performing nuclear magnetic resonance spin echo amplitude measurements at a resonant frequency of hydrogen nuclei in said chamber, and determining a nuclear magnetic relaxation rate of said hydrogen nuclei. 
     
     
       17. The method as defined in  claim 13  further comprising performing nuclear magnetic resonance spin echo measurements in said chamber, at a resonant frequency of sodium-23 ions in aqueous solution, summing amplitudes of said sodium-23 spin echo measurements, and determining a relative concentration of sodium ions in said fluid sample. 
     
     
       18. A method for distinguishing between a first component and a second component in a fluid sample withdrawn from an earth formation and in a chamber on a wireline instrument, comprising:
 (a) performing magnetic resonance spin echo measurements on said fluid sample in said chamber at a selected magnetic resonance frequency;    (b) summing amplitudes of said spin echo measurements;    (c) spectrally analyzing said summed amplitudes in the frequency domain;    (d) determining whether said first component is present in said fluid sample in said chamber by measuring an amplitude of said spectrally analyzed summed amplitudes at a shift characteristic of said first component from said selected resonant frequency; and    (e) determining whether said second component is present in said fluid sample in said chamber by measuring an amplitude of said spectrally analyzed summed amplitudes at a shift characteristic of said second component from said selected frequency.   
     
     
       19. The method as defined in  claim 18  further comprising improving a signal-to-noise ratio of said spin echo measurements by:
 (i) performing spin echo measurements on a first portion of said sample in said chamber during a wait time between sets of said spin echo measurements performed on a second portion of said sample in said chamber, said first portion substantially unaffected by a radio frequency magnetic field used to make said spin echo measurements on said second portion; and    ( ii )  stacking said spin echo measurements made on said first portion and said second portion.     
     
     
       20. The method as defined in  claim 18  further comprising measuring a magnitude of a static magnetic field used to make said spin echo measurements in said chamber and superimposing a selectable magnitude magnetic field on said static magnetic field to compensate for temperature induced changes in said magnitude of said static magnetic field. 
     
     
       21. The method as defined in  claim 18  further comprising performing nuclear magnetic resonance spin echo amplitude measurements at a resonant frequency of hydrogen nuclei in said chamber, and determining a relaxation rate of said hydrogen nuclei. 
     
     
       22. The method as defined in  claim 18  wherein said selected magnetic resonance frequency is associated with carbon- 13 . 
     
     
       23. The method as defined in  claim 18  wherein said first and second components comprise connate fluid and a mud filtrate. 
     
     
       24. An apparatus which characterizes a fluid sample withdrawn from an earth formation, said fluid sample contained within a chamber on a wireline instrument, the method comprising:
 (a) a magnet on said wireline instrument which induces a substantially homogeneous static magnetic field in at least a portion of said sample in said chamber;    (b) a first antenna which induces a radio frequency magnetic field in said portion of said sample in said chamber, said radio frequency magnetic field substantially perpendicular to a magnetization direction of said static magnetic field;    (c) circuits coupled to said antenna which perform nuclear magnetic resonance spin echo measurements at a selected nuclear magnetic resonant frequency, said circuits including means for stacking said spin echo measurements over a measurement sequence; and    (d) a spectral analyzer which measures amplitudes of components of said spin echo measurements at frequency shifts characteristic of a first and second component of said fluid.   
     
     
       25. The apparatus as defined in  claim 24  further comprising:
 (i) at least one additional antenna switchably coupled to said circuits which performs said nuclear magnetic resonance measurements, so that spin echo measurements can be performed during a wait time between measurement sequences performed using said first antenna, on a portion of said fluid sample in said chamber that is substantially unaffected by radio frequency magnetic fields radiated by said first antenna; and    (ii) circuits which stack measurements made by said first antenna and said at least one additional antenna.   
     
     
       26. The apparatus as defined in  claim 24  further comprising circuits selectively coupled to said antenna which perform nuclear magnetic resonance spin echo measurements at a nuclear magnetic resonant frequency of hydrogen nuclei. 
     
     
       27. The apparatus of  claim 24  wherein said selected magnetic resonance frequency corresponds to carbon  13 . 
     
     
       28. The method as defined in  claim 24  wherein said first and second components comprise connate fluid and a mud filtrate. 
     
     
       29. A method which characterizes a fluid sample withdrawn from an earth formation, comprising:
 (a) placing a probe in hydraulic communication with said earth formation, said probe forming part of a wireline formation testing instrument;    (b) withdrawing fluid by operating a pump in selective hydraulic communication with said probe;    (c) conducting said fluid into a sample chamber disposed in said instrument and performing nuclear magnetic resonance measurements on said fluid therein, said measurements comprising magnetic resonant spin echo measurements on said fluid sample in said sample chamber at a selected nuclear magnetic resonant frequency, summing amplitudes of said spin echo measurements, and spectrally analyzing said summed amplitudes;    (d) determining whether a first component is present in said fluid sample by measuring an amplitude of said spectrally analyzed summed amplitudes at a frequency shift from said selected frequency characteristic of said first component; and    (e) determining whether a second component is present in said fluid sample by measuring an amplitude of said spectrally analyzed summed amplitudes at a frequency shift from said selected frequency characteristic of said second component.   
     
     
       30. The method of  claim 29  wherein said selected frequency is associated with carbon- 13 . 
     
     
       31. The method of  claim 29  wherein said first and second components comprise a connate fluid and a mud filtrate.