Neutron method and apparatus for determining total cross-section

Claim 1

A method for quantitatively determining the macroscopic neutron absorption cross-section of a geological formation traversed by a borehole, wherein said method comprises the steps of: a. passing a logging sonde through said borehole while continuously irradiating said formation with a continuous source of neutrons; b. detecting an epithermal neutron flux with a first detector carried by said sonde and spaced from said source of neutrons; c. detecting a thermal neutron flux with a second detector carried by said sonde also spaced from said source of neutrons; d. generating electrical signals indicative of said detected epithermal neutron flux and of said thermal neutron flux; and e. combining said electrical signals indicative of said detected epithermal neutron flux and of said thermal neutron flux to generate a signal representative of the macroscopic neutron absorption cross-section of said geological formation according to the relationship: SIGMA=A+B log (FE)-C log (FT) where SIGMA is the macroscopic neutron absorption cross-section of said material, (FE) is the signal indicative of epithermal neutrons, (FT) is the signal indicative of thermal neutrons, and A,B, and C are constants.

Claim 2

A method for quantitatively determining the macroscopic neutron absorption cross-section of a geological formation traversed by a borehole, wherein said method comprises the steps of: a. passing a logging sonde through said borehole while continuously irradiating said formation with a continuous source of neutrons; b. detecting an epithermal neutron flux with a first detector carried by said sonde and spaced from said source of neutrons; c. detecting a thermal neutron flux with a second detector carried by said sonde also spaced from said source of neutrons; d. generating electrical signals indicative of said detected epithermal neutron flux and of said thermal neutron flux; and e. combining said electrical signals indicative of said detected epithermal neutron flux and of said thermal neutron flux to generate a signal representative of the macroscopic neutron absorption cross-section of said geological formation according to the relationship: SIGMA=A+B log (FE)-C log (FT) where SIGMA is the macroscopic neutron absorption cross-section of said material, (FE) is the signal indicative of epithermal neutrons, (FT) is the signal indicative of thermal neutrons, and A,B, and C are constants.

Claim 3

A method for quantitatively determining the macroscopic neutron absorption cross-section of a geological formation traversed by a borehole, wherein said method comprises the steps of: a. passing a logging sonde through said borehole while continuously irradiating said formation with a continuous source of neutrons; b. detecting an epithermal neutron flux at each one of a first pair of detectors carried by said sonde and spaced different distances from said source of neutrons; c. detecting a thermal neutron flux at each one of a second pair of detectors carried by said sonde and spaced different distances from said source of neutrons; d. generating a first electrical signal indicative of the spatial distribution of epithermal neutrons; e. generating a second electrical signal indicative of the spatial distribution of thermal neutrons; f. combining said first and second electrical signals to generate a signal representative of the macroscopic neutron absorption cross-section of said geological formation.

Claim 4

A method for quantitatively determining the macroscopic neutron absorption cross-section of a geological formation traversed by a borehole, wherein said method comprises the steps of: a. passing a logging sonde through said borehole while continuously irradiating said formation with a continuous source of neutrons; b. detecting an epithermal neutron flux at each one of a first pair of detectors carried by said sonde and spaced different distances from said source of neutrons; c. detecting a thermal neutron flux at each one of a second pair of detectors carried by said sonde and spaced different distances from said source of neutrons; d. generating a first electrical signal indicative of the spatial distribution of epithermal neutrons; e. generating a second electrical signal indicative of the spatial distribution of thermal neutrons; f. combining said first and second electrical signals to generate a signal representative of the macroscopic neutron absorption cross-section of said geological formation.

Claim 6

A method for quantitatively determining the macroscopic neutron absorption cross-section of a material irradiated by a continuous neutron source, wherein said method comprises the steps of: a. deriving a first signal indicative of thermal neutrons emanating from said material; b. deriving a second signal indicative of epithermal neutrons emanating from said material; c. taking the logarithm of said first and second signals to generate first and second logarithm signals respectively; and d. combining said first and second logarithm signals in a linear combination to generate a signal representative of the macroscopic neutron absorption cross-section of the material.

Claim 7

A method for quantitatively determining the macroscopic neutron absorption cross-section of a material irradiated by a continuous neutron source, wherein said method comprises the steps of: a. deriving a first signal indicative of thermal neutrons emanating from said material; b. deriving a second signal indicative of epithermal neutrons emanating from said material; c. taking the logarithm of said first and second signals to generate first and second logarithm signals respectively; and d. combining said first and second logarithm signals in a linear combination to generate a signal representative of the macroscopic neutron absorption cross-section of the material.

Claim 11

A method for quantitatively determining the macroscopic neutron absorption cross-section of a material, wherein said method comprises the steps of: a. irradiating the material with neutrons from a continuous source; b. monitoring radiation emanating from the material to generate a first signal indicative of thermal neutrons; c. monitoring radiation emanating from the material to generate a second signal indicative of epithermal neutrons; d. taking the logarithm of said first and second signals to generate first and second logarithm signals respectively; and e. combining said first and second logarithm signals in a linear combination to generate a signal representative of the macroscopic neutron absorption cross-section of said material.

Claim 12

A method for quantitatively determining the macroscopic neutron absorption cross-section of a material, wherein said method comprises the steps of: a. irradiating the material with neutrons from a continuous source; b. monitoring radiation emanating from the material to generate a first signal indicative of thermal neutrons; c. monitoring radiation emanating from the material to generate a second signal indicative of epithermal neutrons; d. taking the logarithm of said first and second signals to generate first and second logarithm signals respectively; and e. combining said first and second logarithm signals in a linear combination to generate a signal representative of the macroscopic neutron absorption cross-section of said material.

Claim 19

An apparatus for quantitatively determining the macroscopic neutron absorption cross-section of a neutron irradiated material, wherein said apparatus comprises: a. means for deriving a signal indicative of thermal neutrons; b. means for deriving a signal indicative of epithermal neutrons; c. means for taking the logarithms of said thermal and epithermal neutron signals; and d. means for combining said thermal and epithermal neutron logarithm signals to generate a signal representative of the macroscopic neutron absorption cross-section of the material.

Claim 20

An apparatus for quantitatively determining the macroscopic neutron absorption cross-section of a neutron irradiated material, wherein said apparatus comprises: a. means for deriving a signal indicative of thermal neutrons; b. means for deriving a signal indicative of epithermal neutrons; c. means for taking the logarithms of said thermal and epithermal neutron signals; and d. means for combining said thermal and epithermal neutron logarithm signals to generate a signal representative of the macroscopic neutron absorption cross-section of the material.

Claim 21

An apparatus for quantitatively determining the macroscopic neutron absorption cross-section of a material, wherein said apparatus comprises: a. a neutron source for irradiating the material with neutrons; b. detector means for monitoring radiation emanating from the material to generate a signal indicative of thermal neutrons; c. detector means for monitoring radiation emanating from the material to generate a signal indicative of epithermal neutrons; d. means for taking the logarithms of said thermal and epithermal neutron signals; and e. means for combining the logarithms of said thermal and epithermal neutron signals to generate a signal representative of the macroscopic neutron absorption cross-section of said material.

Claim 22

An apparatus for quantitatively determining the macroscopic neutron absorption cross-section of a material, wherein said apparatus comprises: a. a neutron source for irradiating the material with neutrons; b. detector means for monitoring radiation emanating from the material to generate a signal indicative of thermal neutrons; c. detector means for monitoring radiation emanating from the material to generate a signal indicative of epithermal neutrons; d. means for taking the logarithms of said thermal and epithermal neutron signals; and e. means for combining the logarithms of said thermal and epithermal neutron signals to generate a signal representative of the macroscopic neutron absorption cross-section of said material.

Claim 23

An apparatus for quantitatively determining the macroscopic neutron absorption cross-section of a neutron irradiated material, wherein said apparatus comprises: a. first means for deriving a signal indicative of thermal neutrons; b. second means for deriving a signal indicative of thermal neutrons; c. first means for deriving a signal indicative of epithermal neutrons; d. second means for deriving a signal indicative of epithermal neutrons; e. means for taking the ratios of said thermal and said epithermal neutron signals respectively; f. means for generating signals indicative of the logarithms of said thermal and epithermal neutron ratios; and g. means for combining said logarithm signals to generate a signal representative of the macroscopic neutron absorption cross-section of the material.

Claim 24

An apparatus for quantitatively determining the macroscopic neutron absorption cross-section of a neutron irradiated material, wherein said apparatus comprises: a. first means for deriving a signal indicative of thermal neutrons; b. second means for deriving a signal indicative of thermal neutrons; c. first means for deriving a signal indicative of epithermal neutrons; d. second means for deriving a signal indicative of epithermal neutrons; e. means for taking the ratios of said thermal and said epithermal neutron signals respectively; f. means for generating signals indicative of the logarithms of said thermal and epithermal neutron ratios; and g. means for combining said logarithm signals to generate a signal representative of the macroscopic neutron absorption cross-section of the material.

Claim 25

An apparatus for quantitatively determining the macroscopic neutron absorption cross-section of a material, wherein said apparatus comprises: a. a neutron source for irradiating the material with neutrons; b. a pair of spaced detector means for monitoring radiation emanating from the material to generate a pair of signals indicative of thermal neutrons; c. a pair of spaced detector means for monitoring radiation emanating from the material to generate a pair of signals indicative of epithermal neutrons; d. means for determining a ratio signal for each respective pair of signals; e. means for taking the logarithms of each of said ratio signals; and f. means for combining the logarithms of said ratio signals to generate a signal representative of the macroscopic neutron absorption cross-section of said material.

Claim 26

An apparatus for quantitatively determining the macroscopic neutron absorption cross-section of a material, wherein said apparatus comprises: a. a neutron source for irradiating the material with neutrons; b. a pair of spaced detector means for monitoring radiation emanating from the material to generate a pair of signals indicative of thermal neutrons; c. a pair of spaced detector means for monitoring radiation emanating from the material to generate a pair of signals indicative of epithermal neutrons; d. means for determining a ratio signal for each respective pair of signals; e. means for taking the logarithms of each of said ratio signals; and f. means for combining the logarithms of said ratio signals to generate a signal representative of the macroscopic neutron absorption cross-section of said material.

Claim 27

A method for monitoring fluid movements in a geological formation traversed by a well bore including the steps of: a. logging the well bore to generate a first log trace representative of macroscopic neutron absorption cross-section; b. relogging the well bore after the fluids in said geological formation have moved to generate a second log trace representative of macroscopic neutron absorption cross-section; c. comparing said first and second log traces to derive an indication of the movement of fluid in said geological formation, either of said logging or relogging steps comprising the steps of: (i.) passing a logging sonde through said borehole while continuously irradiating said formation with a source of neutrons; (ii.) detecting an epithermal neutron flux with a first detector carried by said sonde and spaced from said source of neutrons; (iii.) detecting a thermal neutron flux with a second detector carried by said sonde also spaced from said source of neutrons; (iv.) generating electrical signals indicative of said detected epithermal neutron flux and of said thermal neutron flux respectively; and (v.) combining said electrical signals indicative of said detected epithermal neutron flux and of said thermal neutron flux to generate a log trace representative of the macroscopic neutron absorption cross-section of said geological formation according to the relationship: SIGMA=A+B log (FE)-C log (FT) where SIGMA is the macroscopic neutron absorption cross-section of said formation, (FE) is the signal indicative of epithermal neutrons, (FT) is the signal indicative of epithermal neutrons, (FT) is the signal indicative of thermal neutrons, and A, B, and C are constants.

Claim 28

A method for monitoring fluid movements in a geological formation traversed by a well bore including the steps of: a. logging the well bore to generate a first log trace representative of macroscopic neutron absorption cross-section; b. relogging the well bore after the fluids in said geological formation have moved to generate a second log trace representative of macroscopic neutron absorption cross-section; c. comparing said first and second log traces to derive an indication of the movement of fluid in said geological formation, either of said logging or relogging steps comprising the steps of: (i.) passing a logging sonde through said borehole while continuously irradiating said formation with a source of neutrons; (ii.) detecting an epithermal neutron flux with a first detector carried by said sonde and spaced from said source of neutrons; (iii.) detecting a thermal neutron flux with a second detector carried by said sonde also spaced from said source of neutrons; (iv.) generating electrical signals indicative of said detected epithermal neutron flux and of said thermal neutron flux respectively; and (v.) combining said electrical signals indicative of said detected epithermal neutron flux and of said thermal neutron flux to generate a log trace representative of the macroscopic neutron absorption cross-section of said geological formation according to the relationship: SIGMA=A+B log (FE)-C log (FT) where SIGMA is the macroscopic neutron absorption cross-section of said formation, (FE) is the signal indicative of epithermal neutrons, (FT) is the signal indicative of epithermal neutrons, (FT) is the signal indicative of thermal neutrons, and A, B, and C are constants.

Claim 29

A method for monitoring fluid movements in a geological formation traversed by a well bore including the steps of: a. logging the well bore to generate a first log trace representative of macroscopic thermal neutron absorption cross-section; b. relogging the well bore after the fluids in said geological formation have moved, to generate a second log trace representative of macroscopic thermal neutron absorption cross-section; c. comparing said first and second logs to derive an indication of the movement of fluid in said geological formation, either of said logging or relogging steps comprising the steps of: i. passing a logging sonde through said borehole while continuously irradiating said formation with a source of neutrons; ii. detecting an epithermal neutron flux at each one of a first pair of detectors carried by said sonde and spaced different distances from said source of neutrons; iii. detecting a thermal neutron flux at each one of a second pair of detectors carried by said sonde and spaced different distances from said source of neutrons; iv. generating a first electrical signal indicative of the spatial distribution of epithermal neutrons; v. generating a second electrical signal indicative of the spatial distribution of thermal neutrons; vi. combining said first and second electrical signals to generate a signal representative of the macroscopic neutron absorption cross-section of said geological formation.

Claim 30

A method for monitoring fluid movements in a geological formation traversed by a well bore including the steps of: a. logging the well bore to generate a first log trace representative of macroscopic thermal neutron absorption cross-section; b. relogging the well bore after the fluids in said geological formation have moved, to generate a second log trace representative of macroscopic thermal neutron absorption cross-section; c. comparing said first and second logs to derive an indication of the movement of fluid in said geological formation, either of said logging or relogging steps comprising the steps of: i. passing a logging sonde through said borehole while continuously irradiating said formation with a source of neutrons; ii. detecting an epithermal neutron flux at each one of a first pair of detectors carried by said sonde and spaced different distances from said source of neutrons; iii. detecting a thermal neutron flux at each one of a second pair of detectors carried by said sonde and spaced different distances from said source of neutrons; iv. generating a first electrical signal indicative of the spatial distribution of epithermal neutrons; v. generating a second electrical signal indicative of the spatial distribution of thermal neutrons; vi. combining said first and second electrical signals to generate a signal representative of the macroscopic neutron absorption cross-section of said geological formation.