Spectral identification of proppant in subterranean fracture zones
First Claim
1. For use in conjunction with a subterranean formation traversed by a borehole, a well logging method comprising the steps of:
- performing across an interval of the well at least one logging operation in each of which a logging tool, having a neutron emitting source and at least one detector sensitive to thermal neutron capture gamma rays, is moved through the borehole and used to generate detector capture gamma ray energy spectra as a function of tool position along the borehole; and
utilizing said capture gamma ray energy spectra obtained during the at least one logging operation to determine the presence of high thermal neutron capture cross section material-containing proppant in the formation and/or the borehole region;
wherein said utilizing comprises distinguishing capture gamma rays from said high thermal neutron capture cross-section material-containing proppant from capture gamma rays produced by thermal neutron reactions with other downhole formation and borehole constituents;
wherein said distinguishing step comprises spectral stripping, least squares fitting, or other spectral processing/deconvolution methods to resolve the capture gamma rays from the high capture cross-section material in the proppant from capture gamma rays originating from other downhole elements/materials; and
wherein said determining in said utilizing step comprises the identification of intervals in the well where capture gamma rays from said high thermal neutron capture cross-section material are detected.
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Accused Products
Abstract
Proppant placed in a subterranean fracture zone is detected with a spectral identification method in which capture gamma ray spectra are obtained during a logging run carried out with a logging tool having a neutron emitting source and at least one detector sensitive to thermal neutron capture gamma rays. Capture gamma rays from one or more high thermal neutron cross-section materials in the proppant are distinguished from capture gamma rays produced by thermal neutron capture reactions with other downhole formation and borehole constituents utilizing a spectral processing/deconvolution technique. The capture gammas rays from the high thermal neutron capture cross section material in the proppant are used to identify propped fracture zones either alone or in combination with other proppant identification methods which rely on measuring thermal neutron related count rates and/or thermal neutron capture cross-sections from neutron, compensated neutron, and/or pulsed neutron capture logging tools.
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Citations
23 Claims
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1. For use in conjunction with a subterranean formation traversed by a borehole, a well logging method comprising the steps of:
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performing across an interval of the well at least one logging operation in each of which a logging tool, having a neutron emitting source and at least one detector sensitive to thermal neutron capture gamma rays, is moved through the borehole and used to generate detector capture gamma ray energy spectra as a function of tool position along the borehole; and utilizing said capture gamma ray energy spectra obtained during the at least one logging operation to determine the presence of high thermal neutron capture cross section material-containing proppant in the formation and/or the borehole region; wherein said utilizing comprises distinguishing capture gamma rays from said high thermal neutron capture cross-section material-containing proppant from capture gamma rays produced by thermal neutron reactions with other downhole formation and borehole constituents; wherein said distinguishing step comprises spectral stripping, least squares fitting, or other spectral processing/deconvolution methods to resolve the capture gamma rays from the high capture cross-section material in the proppant from capture gamma rays originating from other downhole elements/materials; and wherein said determining in said utilizing step comprises the identification of intervals in the well where capture gamma rays from said high thermal neutron capture cross-section material are detected. - View Dependent Claims (2, 3, 4, 5)
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6. For use in conjunction with a subterranean formation traversed by a borehole, a well logging method comprising the steps of:
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performing across an interval of the well at least one logging operation in each of which a logging tool, having a neutron emitting source and at least one detector sensitive to thermal neutron capture gamma rays, is moved through the borehole and used to generate detector capture gamma ray energy spectra as a function of tool position along the borehole; and utilizing said capture gamma ray energy spectra obtained during the at least one logging operation to determine the presence of high thermal neutron capture cross section material-containing proppant in the formation and/or the borehole region; wherein said utilizing comprises distinguishing capture gamma rays from said high thermal neutron capture cross-section material-containing proppant from capture gamma rays produced by thermal neutron reactions with other downhole formation and borehole constituents; wherein said distinguishing step comprises spectral stripping, least squares fitting, or other spectral processing/deconvolution methods to resolve the capture gamma rays from the high capture cross-section material in the proppant from capture gamma rays originating from other downhole elements/materials; wherein said determining in said utilizing step comprises the identification of intervals in the well where capture gamma rays from said high thermal neutron capture cross-section material are detected; wherein said proppant was emplaced in the formation and/or borehole region via induced fracturing operations; and wherein said at least one logging operation comprises a first logging operation before induced fracturing operations and a second logging operation after the induced fracturing operations, and wherein said distinguishing step further comprises comparing or combining capture gamma ray energy spectra obtained in said first logging operation with capture gamma ray energy spectra obtained during said second logging operation. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. For use in conjunction with a subterranean formation traversed by a borehole, a well logging method comprising the steps of:
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performing across an interval of the well at least one logging operation in each of which a logging tool, having a neutron emitting source and at least one detector sensitive to thermal neutron capture gamma rays, is moved through the borehole and used to generate detector capture gamma ray energy spectra as a function of tool position along the borehole; and utilizing said capture gamma ray energy spectra obtained during the at least one logging operation to determine the presence of high thermal neutron capture cross section material-containing proppant in the formation and/or the borehole region; wherein said utilizing comprises distinguishing capture gamma rays from said high thermal neutron capture cross-section material-containing proppant from capture gamma rays produced by thermal neutron reactions with other downhole formation and borehole constituents; wherein said distinguishing step comprises spectral stripping, least squares fitting, or other spectral processing/deconvolution methods to resolve the capture gamma rays from the high capture cross-section material in the proppant from capture gamma rays originating from other downhole elements/materials; wherein said determining in said utilizing step comprises the identification of intervals in the well where capture gamma rays from said high thermal neutron capture cross-section material are detected; wherein said proppant was emplaced in the formation and/or borehole region via induced fracturing operations; and wherein said determining step further incorporates a comparison of count rates obtained with a neutron logging tool containing at least one thermal neutron detector during a first logging operation conducted before induced fracturing operations with count rates obtained with a corresponding neutron tool during a second logging operation conducted after the fracturing operations. - View Dependent Claims (14)
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15. For use in conjunction with a subterranean formation traversed by a borehole, a well logging method comprising the steps of:
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performing across an interval of the well at least one logging operation in each of which a logging tool, having a neutron emitting source and at least one detector sensitive to thermal neutron capture gamma rays, is moved through the borehole and used to generate detector capture gamma ray energy spectra as a function of tool position along the borehole; and utilizing said capture gamma ray energy spectra obtained during the at least one logging operation to determine the presence of high thermal neutron capture cross section material-containing proppant in the formation and/or the borehole region; wherein said utilizing comprises distinguishing capture gamma rays from said high thermal neutron capture cross-section material-containing proppant from capture gamma rays produced by thermal neutron reactions with other downhole formation and borehole constituents; wherein said distinguishing step comprises spectral stripping, least squares fitting, or other spectral processing/deconvolution methods to resolve the capture gamma rays from the high capture cross-section material in the proppant from capture gamma rays originating from other downhole elements/materials; wherein said determining in said utilizing step comprises the identification of intervals in the well where capture gamma rays from said high thermal neutron capture cross-section material are detected; wherein said proppant was emplaced in the formation and/or borehole region via induced fracturing operations; and
;wherein said determining step further incorporates a comparison of measured near and/or far detector count rates obtained with a compensated neutron logging tool in a logging operation conducted after the fracturing operation with corresponding computed detector count rates obtained utilizing relationships developed between the compensated neutron logging tool near/far detector count rate ratio and the measured detector count rates during the same logging operation. - View Dependent Claims (16)
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17. For use in conjunction with a subterranean formation traversed by a borehole, a well logging method comprising the steps of:
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performing across an interval of the well at least one logging operation in each of which a logging tool, having a neutron emitting source and at least one detector sensitive to thermal neutron capture gamma rays, is moved through the borehole and used to generate detector capture gamma ray energy spectra as a function of tool position along the borehole; and utilizing said capture gamma ray energy spectra obtained during the at least one logging operation to determine the presence of two or more high thermal neutron capture cross section materials contained in proppant placed in the formation and/or the borehole region; wherein said utilizing comprises distinguishing capture gamma rays from said high thermal neutron capture cross-section materials-containing proppant from capture gamma rays produced by thermal neutron reactions with other downhole formation and borehole constituents; wherein said distinguishing step comprises spectral stripping, least squares fitting, or other spectral processing/deconvolution methods to resolve the capture gamma rays from any of the two or more high capture cross-section materials in the proppant from capture gamma rays originating from other downhole elements/materials; and wherein said determining in said utilizing step comprises the identification of intervals in the well where capture gamma rays from any of said two or more high thermal neutron capture cross-section materials are detected. - View Dependent Claims (18, 19)
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20. For use in conjunction with a subterranean formation traversed by a borehole, a well logging method comprising the steps of:
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performing across an interval of the well two logging operations in each of which a logging tool, having a neutron emitting source and at least one detector sensitive to thermal neutron capture gamma rays, is moved through the borehole and used to generate detector capture gamma ray energy spectra as a function of tool position along the borehole; and utilizing said capture gamma ray energy spectra obtained during each logging operation to determine changes in the presence of high thermal neutron capture cross section material-containing proppant in the formation and/or the borehole region between the two logging operations; wherein said utilizing comprises distinguishing capture gamma rays from said high thermal neutron capture cross-section material-containing proppant from capture gamma rays produced by thermal neutron reactions with other downhole formation and borehole constituents; wherein said distinguishing step comprises spectral stripping, least squares fitting, or other spectral processing/deconvolution methods to resolve the capture gamma rays from the high capture cross-section material in the proppant from capture gamma rays originating from other downhole elements/materials; and wherein said determining in said utilizing step comprises the identification of intervals in the well where the intensity/number of capture gamma rays from said high thermal neutron capture cross-section material in the first of the two logging operations is different from the intensity/number of capture gamma rays from said high thermal neutron capture cross section material in the second logging operation. - View Dependent Claims (21, 22, 23)
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Specification