Abstract: Determining a value indicative of hydrogen index. At least some of the example embodiments are methods including obtaining an inelastic count rate and a capture count rate of a first gamma detector for a particular borehole depth, obtaining an inelastic count rate and a capture count rate of a second gamma detector for the particular borehole depth, calculating a ratio of an inelastic count rate to a capture count rate for the first gamma detector, thereby creating a first value, calculating a ratio of an inelastic count rate to a capture count rate for the second gamma detector, thereby creating a second value, calculating a ratio of the first and second values, and determining a value indicative of hydrogen index based on the ratio of the first and second values.

Abstract: A method, in some embodiments, comprises lowering a neutron wireline tool into a cased borehole containing casing fluid, determining a ratio of inelastic count rate to capture count rate using gammas passing through the casing fluid, and calculating a capture cross section of the casing fluid using the ratio.

Abstract: A method, in some embodiments, comprises lowering a neutron wireline tool into a cased borehole containing casing fluid, determining a ratio of inelastic count rate to capture count rate using gammas passing through the casing fluid, and calculating a capture cross section of the casing fluid using the ratio.

Abstract: Determining a value indicative of gas saturation of a formation. At least some of the illustrative embodiments are methods including: obtaining an inelastic count rate and a capture count rate of a gamma detector for a particular borehole depth; removing at least a portion of the chlorine response from the capture count rate, thereby creating a modified capture count rate; calculating a ratio of an inelastic count rate to the modified capture count rate for the particular borehole depth; determining a value indicative of gas saturation based on the ratio; and producing a plot of the value indicative of gas saturation as a function of borehole depth for a formation that the borehole at least partially penetrates.

Abstract: Determining a value indicative of hydrogen index. At least some of the example embodiments are methods including obtaining an inelastic count rate and a capture count rate of a first gamma detector for a particular borehole depth, obtaining an inelastic count rate and a capture count rate of a second gamma detector for the particular borehole depth, calculating a ratio of an inelastic count rate to a capture count rate for the first gamma detector, thereby creating a first value, calculating a ratio of an inelastic count rate to a capture count rate for the second gamma detector, thereby creating a second value, calculating a ratio of the first and second values, and determining a value indicative of hydrogen index based on the ratio of the first and second values.

Abstract: Predicting gas saturation of a formation using neural networks. At least some of the illustrative embodiments include obtaining a gamma count rate decay curve one each for a plurality of gamma detectors of a nuclear logging tool (the gamma count rate decay curves recorded at a particular borehole depth), applying at least a portion of each gamma count rate decay curve to input nodes of a neural network, predicting a value indicative of gas saturation of a formation (the predicting by the neural network in the absence of a formation porosity value supplied to the neural network), and producing a plot of the value indicative of gas saturation of the formation as a function of borehole depth.

Abstract: Determining a value indicative of gas saturation of a formation. At least some of the illustrative embodiments are methods including: obtaining an inelastic count rate and a capture count rate of a gamma detector for a particular borehole depth; removing at least a portion of the chlorine response from the capture count rate, thereby creating a modified capture count rate; calculating a ratio of an inelastic count rate to the modified capture count rate for the particular borehole depth; determining a value indicative of gas saturation based on the ratio; and producing a plot of the value indicative of gas saturation as a function of borehole depth for a formation that the borehole at least partially penetrates.

Abstract: Processing gamma count rate decay curves using neural networks. At least some of the illustrative embodiments are methods comprising obtaining a gamma count rate decay curve one each for a plurality of gamma detectors of a nuclear logging tool (the gamma count rate decay curves recorded at a particular borehole depth), applying the gamma count rate decay curves to input nodes of a neural network, predicting by the neural network a geophysical parameter of the formation surrounding the borehole, repeating the obtaining, applying and predicting for a plurality of borehole depths, and producing a plot of the geophysical parameter of the formation as a function of borehole depth.

Abstract: Determining a value indicative of gas saturation of a formation. At least some of the illustrative embodiments are methods including obtaining an inelastic count rate and a capture count rate of a gamma detector for a particular borehole depth, calculating a ratio of an inelastic count rate to a capture count rate for the particular borehole depth, determining a value indicative of gas saturation based on the ratio of the inelastic count rate to the capture count rate for the particular borehole depth, repeating the obtaining, calculating and determining for a plurality of borehole depths, and producing a plot of the value indicative of gas saturation of the formation as a function of borehole depth.

Abstract: Predicting gas saturation of a formation using neural networks. At least some of the illustrative embodiments include obtaining a gamma count rate decay curve one each for a plurality of gamma detectors of a nuclear logging tool (the gamma count rate decay curves recorded at a particular borehole depth), applying at least a portion of each gamma count rate decay curve to input nodes of a neural network, predicting a value indicative of gas saturation of a formation (the predicting by the neural network in the absence of a formation porosity value supplied to the neural network), and producing a plot of the value indicative of gas saturation of the formation as a function of borehole depth.

Abstract: A method and related system of determining formation density by compensating actual inelastic gamma rays detected from a pulsed-neutron tool for the effects of neutron transport. The method and systems may model response of the tool and use the modeled response as an indication of an amount to compensate detected inelastic gamma rays.

Abstract: A method and system for calculating extent of a formation treatment material in a formation. At least some of the illustrative embodiments are methods comprising releasing neutrons into a formation from a neutron source of a logging tool within a borehole having an axis, sensing energies of gammas produced by materials in the formation, the sensing by a gamma detector on the logging tool, generating a measured spectrum of the energies of the gammas sensed by the gamma detector, determining elemental concentrations of materials in the formation based on a basis spectrum, and calculating axial extent of a formation treatment material in the formation in relation to the axis of the borehole based on the elemental concentrations of at least some materials in the formation.

Abstract: Processing gamma count rate decay curves using neural networks. At least some of the illustrative embodiments are methods comprising obtaining a gamma count rate decay curve one each for a plurality of gamma detectors of a nuclear logging tool (the gamma count rate decay curves recorded at a particular borehole depth), applying the gamma count rate decay curves to input nodes of a neural network, predicting by the neural network a geophysical parameter of the formation surrounding the borehole, repeating the obtaining, applying and predicting for a plurality of borehole depths, and producing a plot of the geophysical parameter of the formation as a function of borehole depth.

Abstract: Determining a value indicative of gas saturation of a formation. At least some of the illustrative embodiments are methods including obtaining an inelastic count rate and a capture count rate of a gamma detector for a particular borehole depth, calculating a ratio of an inelastic count rate to a capture count rate for the particular borehole depth, determining a value indicative of gas saturation based on the ratio of the inelastic count rate to the capture count rate for the particular borehole depth, repeating the obtaining, calculating and determining for a plurality of borehole depths, and producing a plot of the value indicative of gas saturation of the formation as a function of borehole depth.

Abstract: A method and system for calculating extent of a formation treatment material in a formation. At least some of the illustrative embodiments are methods comprising releasing neutrons into a formation from a neutron source of a logging tool within a borehole having an axis, sensing energies of gammas produced by materials in the formation, the sensing by a gamma detector on the logging tool, generating a measured spectrum of the energies of the gammas sensed by the gamma detector, determining elemental concentrations of materials in the formation based on a basis spectrum, and calculating axial extent of a formation treatment material in the formation in relation to the axis of the borehole based on the elemental concentrations of at least some materials in the formation.

Abstract: A method and related system of determining formation density by compensating actual inelastic gamma rays detected from a pulsed-neutron tool for the effects of neutron transport. The method and systems may model response of the tool and use the modeled response as an indication of an amount to compensate detected inelastic gamma rays.

Abstract: A typical nuclear well logging tool forms a count rate data stream including statistical noise. A robust single pass partially deconvolved smoothing filter matched to the tool response is applied to the count rate data to enhance vertical resolution while minimizing the statistical noise increase. The smoothing filter is partially deconvolved by the application of a three point deconvolution characteristic of the cusp portion of a related cusp function and a box function representative of the tool response.

Abstract: A method for providing gain stabilization to a nuclear spectroscopy tool by use of gross features of largely invariant spectra. A particle or gamma ray energy spectrum of an earth formation and wellbore are measured. A ratio of the number of particles or gamma rays measured in a first energy window to the number of particles or gamma rays measured in a second energy window is calculated. The gain of the nuclear spectroscopy tool is adjusted as a function of the calculated ratio. The first energy window is selected to span substantially an entire range of measured energies for the spectrum and the second energy window is selected to span an upper range of the measured energies for the spectrum.

Abstract: A system for measuring fast neutron induced gamma ray energy spectra in cased wellbores. The system includes an electronic source of monoenergetic 14 MeV fast neutrons, a high density bismuth germanate scintillation detector, a downhole pulse height analyzer and a highly accurate gain stabilizer circuit. The gain stabilization utilizes the iron (Fe) edge in the catpure gamma ray spectrum to establish system gain since iron is always present in the tool case and the wellbore casing.

Abstract: An efficient spatial smoothing algorithm for filtering data while preserving spatial detail is obtained using the system (impulse response) function of the sensor. In contrast to the normal procedure for determining the filter coefficients for an arbitrary system function, this technique avoids the use of Fourier transforms. The spatial filtering coefficients are obtained analytically for the frequently applicable Gaussian system function. The efficiency of this procedure is illustrated by filtering discrete data. For realtime smoothing of nuclear log data, a filter length of five times the vertical resolution is required.