Abstract: Methods and systems are described for using pulsed neutron ?-ray spectroscopy to measure formation water salinity from within a bore-hole. Through generating a cross-plot of database values of ratios of spectroscopically determined yields of hydrogen (H) and chlorine (Cl) from two detectors, deriving apparent salinities therefrom, formation and borehole water salinities can be determined.

Abstract: A method and apparatus for calibrating readings of a downhole tool are provided. The method including collecting data representative of gamma ray photon energies detected by a downhole tool during the well-logging, a spectrum of the gamma ray photon energies detected by the downhole tool having a derivative with respect to the gamma ray photon energies. The method and program comprise calibrating the readings of the downhole tool using at least one predetermined correction factor based on the derivative of the spectrum of the gamma ray photon energies detected by the downhole tool. A computer-readable program storage device and a computer programmed to perform a set of instructions are also provided.

Abstract: A method and apparatus are provided for correcting gamma ray data representative of gamma ray energies for spectral degradation. The method and apparatus include degrading reference gamma ray spectra. At least one correction factor is calculated between the degraded gamma ray spectra and the reference gamma ray spectra. The gamma ray data are then corrected using a calculated correction factor. Another method is provided for determining a correction factor for correcting data representative of gamma ray energies for spectral degradation. The method includes disposing a downhole tool in a simulated environment representative of actual downhole conditions, the tool including a neutron source and at least one gamma ray detector. The temperature of at least one of the gamma ray detectors of the tool is then varied while the simulated environment is irradiated with neutrons emitted from the neutron source.

Abstract: The invention described herein provides for an intelligent or "adaptable" filtering method that could be applied when filtering log data. In the present invention, for a given filter model, the adaptive filtering technique differentiates between true changes in the formation or borehole quantity measured and what can be considered to be just a "statistical fluctuation". So, when in long constant-value intervals (data deviations do not exceed those predicted by statistical theory) the filter will automatically increase the number of filter levels used, thereby providing a large reduction (smoothing) of the statistical variations. However, when approaching a spot where there is a true change in the quantity being measured (data deviations over and above those predicted by statistics) the filter will automatically and smoothly decrease, on both sides of this spot, thereby preserving the sharpness of the bed boundary or borehole fluid contact and also preserving the true shape of a thin geologic bed.

Abstract: The present invention provides a new method to determine corrected characteristics of materials using the measured quantities obtained by a measurement and an extensive set of database points representing laboratory and modeled results in well defined environments. In particular the invention relates to the measurement of the characteristics of the formation around a wellbore as well as of the borehole with a well logging tool. Using a dynamic parametrization technique, the environmental corrections and the transformations from the measured to the physical characteristics can be achieved in a more accurate, robust and flexible way. The dynamic local parametrization is based on a weighted multiple linear regression over the entire database to obtain the local coefficients for the transformation which can be expressed as a simple equation.

Abstract: A method for measuring formation density corrected for activated gamma radiation. The formation adjacent the borehole is irradiated with low energy gamma radiation from a density tool source. At least one gamma ray detection means is spaced longitudinally from the source. A gamma ray spectrum containing gamma rays that result from density source radiation and also activated gamma rays is detected by the detection means. The activated gamma rays are identified and subtracted from the total number of detected gamma rays which results in the gamma ray count from the density tool source. This gamma ray count can then be used in conventional density calculation processes to determine formation density that has been corrected for activated gamma rays caused by naturally occurring gamma radiation and from other logging equipment that induces gamma radiation.

Abstract: The invention relates to a novel method and apparatus for the cyclical timing of the neutron bursts, spectral gates, tau determination gates, and background measurement periods in a capture spectroscopy measurement. Each measurement cycle period is divided in time into 62 tau units, where tau is the thermal decay time constant determined from the immediately preceding cycle period. The neutron accelerator bursts eight times, each burst lasting for one tau unit and beginning at 0, 6, 12, . . . 42 taus. The capture spectral gates, two units long, follow each neutron burst after a one tau unit long delay. Spectral background due to activation is measured in a long background window until tau equals 61, following a two tau delay from the eighth spectral gate and, properly normalized, is subtracted on a channel-by-channel basis from the spectrum accumulated from the capture spectral gates. Tau determination gates I and II follow each neutron burst after a two tau delay.