Abstract: A method for evaluating a formation includes determining a number of detected gamma rays resulting from imparting neutrons into a formation. The detected gamma rays are each characterized by an energy level thereof. The gamma rays are detected at a first distance from a position of imparting the neutrons into the formation. Those of the detected gamma rays attributable to neutron capture by hydrogen nuclei are removed from the number of detected gamma rays. The number of detected gamma rays having hydrogen neutron capture gamma rays removed therefrom are used to calculate a property of the formation.

Abstract: The system and method provide security and cargo handling personnel a versatile tool to rapidly check cargo for hidden radiological materials, explosives, drugs, and chemical weapons material. Gamma ray emission is stimulated by a pulsed neutron source. The gamma ray signature is used to classify the material. Passive gamma ray analysis can be used to detect and identify radiological material. The method of determining the contents of a target includes irradiating a target; detecting at least one spectrum emitted from the target; performing a primary analysis to extract a first set of indicators; and performing a secondary analysis to decide the contents of the target. The primary analysis utilizes either a least squares analysis or principal component analysis. The secondary analysis utilizes a generalized likelihood ratio test or support vector machines.

Abstract: A well logging tool has a neutron source for irradiating formation surrounding a borehole. Two detectors are mounted in a spaced-apart vertical relationship within the tool pressure-resistant housing. Each detector detects capture gamma radiation across the entire gamma ray energy spectrum, windows are set in this spectrum to separate two distinct energy ranges, thereby generating a total of four independent sets of signals, two for each detector. One set of signals is indicative of the hydrogen content and insensitive to the chlorine content of the irradiated formation. The second set of signals is indicative of the hydrogen plus the chlorine content of the irradiated formation. By comparing the sets of signals in two proportional energy ranges, the logging tool allows to generate a log that helps determine the presence or absence of hydrocarbon or salt water in the formation.

Abstract: An apparatus and method non-invasively interrogates an object to detect contraband. The apparatus irradiates the object with fast neutrons of energy greater than 6.7 MeV, and measures the ensuing gamma-ray spectra. Irradiation of the object is accomplished by producing a neutron beam and moving the interrogated object stepwise or continuously relative to the beam. The nuclear interactions of highly penetrating neutrons within the irradiated volume of the object give rise to energetic nuclear-species characteristic gamma-rays. The energy and intensity of the emitted gamma-rays provide information relative to the spatial and density distributions of the gamma-ray sources, i.e., the specific atomic nuclei within the object. From this information, three-dimensional images of the atomic nuclei spatial and density distributions are inferred. Such three-dimensional images allow a decision to be made as to the presence of contraband. Measurements are made using arrays of gamma-ray scintillator detectors.

Abstract: A system and method for detecting contraband generates a highly collimated beam of pulsed fast neutrons, having a pulse width on the order of a nanosecond, and an energy of 5 to 9 MeV. An object under investigation is scanned with the collimated pulsed beam. The neutrons in the beam cause (n, .gamma.) reactions in a limited object volume or voxel, defined by the intersection of the collimated beam and the scanned object. The highly penetrating fast neutrons produce nuclear reactions with the atomic elements present within the object, causing gamma rays to be emitted. By measuring the approximate time of flight of the neutron pulse, a determination is made as to the particular voxel from which the gamma ray originated. The energy of the detected gamma rays identifies the particular elements from which the gamma rays originated. Thus, e.g., the carbon, nitrogen, oxygen, and chlorine content, which elements are commonly found in contraband, of a particular voxel can be determined directly and precisely.

Abstract: A method and apparatus for determining true formation porosity utilize downhole measurement-while-drilling neutron porosity measurement devices. A initial measurement is taken shortly after the formation is bored and before any substantial invasion by the drilling fluid occurs. Subsequent measurements are made until a steady, no longer increasing, measurement is reached indicating saturation of the formation by the drilling fluid to the depth of the measurements. The steady measurement is indicative of the true porosity of a gas containing formation while the difference between the initial and steady measurements is indicative of the gas saturation of a gas containing formation.