Abstract: Methods and apparatus are provided for determining the content of a first element in a formation which cannot otherwise be determined via a capture spectrum measurement. The methods and apparatus utilize the inelastic spectrum measurement of the first element and the inelastic and capture spectrum measurements of at least a second element. The methods and apparatus have particular application to determining the carbon content of a formation although they are not limited thereto. The inelastic and capture spectrum measurements of silicon are useful in making such determinations, although other chemical elements may be used as the second element.

Abstract: A method for determining the porosity of an underground formation includes the steps of irradiating the formation with neutrons, detecting and measuring gamma rays resulting from irradiation of the formation, discriminating between gamma rays from the formation and gamma rays from the tool, and using a measurement of the gamma rays from the tool to determine the formation porosity. A suitable logging tool includes a neutron source, a gamma ray detector, means for discriminating between gamma rays from the formation and gamma rays from the tool, and means for relating the gamma rays from the tool to the formation porosity.

Abstract: The energy-to-channel response of a bismuth germanate scintillator (BGO) gamma ray spectra measurement system is calibrated by use of the 10.2 MeV gamma ray peak originating from epithermal neutron capture within the BGO crystal as a calibration reference line. The 10.2 MeV peak is located by successively fitting the detected spectrum to the combination of a gaussian-shaped gamma ray peak and an exponentially-shaped background, beginning at the upper end of the spectrum and successively sliding the fitting window downwards until the peak is reached. Once the 10.2 MeV peak has been located, the spectral gain is adjusted to shift the peak to an assigned calibration channel location adjacent the upper end of the overall spectral window.

Abstract: Logging method and tool string for identifying and determining the concentrations of subsurface formation elements next to a borehole, by (i) using a broad energy spectra neutron source (such as a chemical source, like AmBe), and (ii) detecting and counting the delayed gamma rays resulting from the activation by the neutrons of atoms of least one element of interest (e.g. aluminum). Two gamma ray detectors may also be disposed on either side of the broad energy spectra neutron source, for detecting and counting the prompt gamma rays resulting from the capture of neutrons by atoms of elements, such as Si, Ca, Fe, S, H, or Cl, Gd, Ti, or K.The broad energy spectra neutron source is used for both the "activation" and the "capture" measurements. The tool string may also include a natural gamma ray tool for the determination of uranium, thorium and potassium, and for measuring the background to be subtracted from the gross Al activation measurement.

Abstract: Logging method and tool string for identifying and determining the concentrations of subsurface formation elements next to a borehole, by (i) using a low energy neutron source (either a chemical source, e.g. a .sup.252 Cf, or a deuterium-deuterium electronic source), and (ii) detecting and counting the delayed gamma rays resulting from the activation by the neutrons of atoms of at least one element of interest (e.g. aluminum). Two gamma ray detectors may also be disposed on either side of the low energy neutron source, for detecting and counting the prompt gamma rays resulting from the capture of neutrons by atoms of elements, such as Si, Ca, Fe, S, H, or Cl, Gd, Ti, or K.The low energy neutron source is used for both the "activation" and the "capture" measurements. The tool string may also include a natural gamma ray tool for the determination of uranium, thorium and potassium, and for measuring the background to be subtracted from the gross Al activation measurement.

Abstract: Logging apparatus and methods for detecting first signals indicative of the absolute concentrations of the first category of elements in the rock matrix, for irradiating the formation with a pulse of high energy neutrons and for detecting a second signal indicative of the relative concentrations of a second category of elements in a rock matrix. The absolute and relative concentrations of a plurality of elements are determined, and this information is used to transform at least one of the relative concentrations into an absolute concentration. One of the measured absolute concentrations is for aluminum, from which correlations are used to determine the absolute concentrations of other, non-measured elements. A tool system for measuring the absolute aluminum concentration includes a californium-252 source and a gamma ray detector having a plurality of windows from which the aluminum count rate can be compensated for interference by manganese activation.

Abstract: A golf accessory for retrieving golf balls, repairing divots and placing ball markers, the accessory including a planar member having a ball holder section formed on one side and a flexible ball guide section on the opposite side for biasing the ball into the holder, the guide section including a pair of tapered tines for repairing divots and placing golf ball markers on the green.

Abstract: Capture gamma ray spectroscopy measurements of earth formations traversed by a borehole are corrected for the influence thereon of the geometry and constituents of the borehole, thereby affording more accurate measurements of the spectral contributions from the formation elements. A partition factor is determined for each separate homogeneous region in the borehole/formation measurement environment, i.e., the tool, the borehole fluid, the casing (if present), the cement annulus (if present), and the formation, and these factors are plugged into predetermined elemental yield relationships, for the elements for which capture spectral measurements are made, to determine the volumetric fractions of such elements (or minerals containing such elements) in the formation.

Abstract: In the illustrative embodiments of the invention disclosed, a more accurate elemental analysis of an earth formation surrounding a borehole is achieved by comparing a gamma ray energy spectrum measured in the borehole, following irradiation of the borehole and the surrounding earth formation with high-energy neutrons, with a composite spectrum made up of a combination of weighted standard spectra of elements postulated to have contributed significantly to the borehole spectrum, wherein the standard spectra include a tool background spectrum that accounts for the spectral contribution due to neutron interactions with the tool constituents. The tool background spectrum is derived by isolating the tool contribution to one or more of the elemental standard spectra, and by using one or a combination of such isolated tool contribution spectra as the tool background spectrum.

Abstract: The composition of a geological formation traversed by a borehole is investigated by measuring an energy spectrum of the radiation within the borehole. The measured spectrum is thereafter analyzed by comparing it with a composite spectrum, made up of standard spectra of constituents postulated to comprise the formation-borehole system. As a result of such analysis, the proportions of the postulated constituents in the formation are determined. Where the measured spectrum is subject to degradation due to changes in the resolution of the detector, a filtering arrangement effects modification of the standard spectra in a manner which provides for a more accurate determination of the constituents of the borehole-formation system.

Abstract: The composition of an earth formation is investigated by repetitively irradiating the formation with bursts of incident radiation and generating an unknown energy spectrum from radiation resulting from the interaction of the incident radiation with nuclei of the formation. A background energy spectrum is generated from radiation detected during a time interval adjacent to the interval in which the unknown energy spectrum is measured. A percentage of the background spectrum, shifted to have the best energy-versus-channel number match with that of the unknown spectrum, is then subtracted from the unknown spectrum to produce an improved, unknown spectrum substantially free of background contributions from which an improved, compensated, inelastic neutron interaction log may be generated.