Abstract: A method of simply and quickly determining ?-ray releasing nuclides having long half-life without carrying out a chemical separation is provided. By inputting a data of pulses incident to an ?-ray detector in a computer, obtaining time distribution of the incident pulses by using a very short time measuring timer and plotting, and fitting the linear originated in a random event corresponding to the background and the non-linear originated in the correlated events of parent nuclides-progenies by using the least squares method, the whole generating probability P (t) from the parent nuclide to the progeny thereof is obtained. By subtracting the random events portion from the P(t), the correlated events portion is extracted. The radioactivity per unit can be obtained by dividing the extracted correlated events portion by the measured time, the amount of the supplied sample and the counting efficiency.

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 for detecting failures in a natural gas returning radiation from the pipeline; determining that there is a failure in the pipeline when the spectral or thermal signature indicates that there is a plume of escaping natural gas from the pipeline emitted from a failure; and indicating to a customer that a failure in the pipeline has been detected at a predetermined coordinate position.

Abstract: Methods and apparatus for continuous real-time measurement of bulk material using gamma irradiation and neutron irradiation. A DGA device monitors bulk material flow and produces a spectrum that is compared to a baseline spectrum to produce a relative weight/impurity ratio. A PGNAA device monitors the same bulk material flow and produces a spectrum that is compared to a library of spectrums to produce a relative component ratio. The relative component ratio is processed with the relative weight/impurity ratio to produce an absolute weight and impurity value, which is then processed with the relative component ratio to produce absolute component, or analyte, values.

Abstract: A method for measuring one or more characteristics of an earth formation wherebyenergy is emitted circumferentially about a borehole into the formation, and the amount reflected back is detected during a plurality of sample periods. The samples are grouped into two or more groups by the azimuthal sector in which the sample was collected. Within a group, each sample is mathematically weighted according to the standoff of the detector from the borehole wall when the sample was taken. Within a group, the weighted samples are summed to produce a weighted total amount of energy detected within a sector. The weighted total is then transformed into the one or more characteristics.

Abstract: A method for formation logging includes acquiring measurements of neutron-induced signals having azimuthal information using a neutron tool; processing the measurements into a plurality of azimuthal sector data for each acquisition interval; and deriving a selected parameter from the plurality of azimuthal sector data. A logging tool includes a housing adapted to move in a borehole; a circuitry having memories for storing neutron-induced measurements; a neutron source disposed in the housing; and at least one detector bank disposed in the housing spaced apart from the neutron source, wherein each of the at least one detector bank comprises at least one detector disposed around a periphery of the housing such that the at least one detector is more sensitive to signals from an azimuthal direction, and wherein count rates detected by each of the at least one detector are separately stored in the memories.

Abstract: A gas detection method includes carrying out respective neutron and density logs, using neutron and density detectors, along a length of well. The density log is corrected for the dimensions and properties of the well casing. The corrected density log is then combined with the neutron log to compensate for regions of artificially high density outside the casing. The compensated density log is continuously calibrated against the neutron log. The dynamically calibrated density and neutron logs are inspected for crossovers that signify the presence of gas in a formation.

Abstract: A method of determining formation density in a cased hole environment using a logging tool having a gamma ray source, a long spacing detector, and a short spacing detector that includes developing one or more cased hole calibration relationships that utilize differences between scattered gamma rays observed by short spacing detectors and scattered gamma rays observed by long spacing detectors to determine corrected formation density values, and using the cased hole calibration relationships and scattered gamma ray measurements obtained by the long spacing detector and the short spacing detector to determine the formation density. An associated article of manufacture and computerized well logging system are also described.

Abstract: Methods and systems for continuously transferring balancing mass to a rotating system or rotating device in order to dynamically balance the rotating system or rotating device are disclosed. A flow of balancing mass can be continuously provided to the rotating system at a controlled flow rate. A pump integrated with the rotating system can be utilized to provide via pump the flow of the balancing mass to the rotating system at a controlled flow rate. The flow of balancing mass can be thereafter discharged at a shutter device integrated with the rotating system, such that the balancing mass passes through a window of the shutter device if the window is open. The balancing mass is passed through the window so as to be transferred to the rotating device at predetermined locations, thereby contributing to the balancing of the rotating system. The balancing mass is generally automatically recirculated through the rotating system if the window of the shutter device is closed.

Abstract: A method for formation logging includes acquiring measurements of neutron-induced signals having azimuthal information using a neutron tool; processing the measurements into a plurality of azimuthal sector data for each acquisition interval; and deriving a selected parameter from the plurality of azimuthal sector data. A logging tool includes a housing adapted to move in a borehole; a circuitry having memories for storing neutron-induced measurements; a neutron source disposed in the housing; and at least one detector bank disposed in the housing spaced apart from the neutron source, wherein each of the at least one detector bank comprises at least one detector disposed around a periphery of the housing such that the at least one detector is more sensitive to signals from an azimuthal direction, and wherein count rates detected by each of the at least one detector are separately stored in the memories.

Abstract: Techniques for monitoring a pulsed neutron source include measuring a burst count rate while the pulsed neutron source is turned on using a monitor detector disposed proximate the pulsed neutron source; measuring a decay count rate while the neutron source is turned off using the monitor detector; and deriving a source strength indicator from the burst count rate and the decay count rate. A pulsed neutron tool includes a tool body; a pulsed neutron source disposed in the tool body; a monitor detector disposed in the tool body proximate the pulsed neutron source; at least one measurement detector disposed in the tool body at a predetermined distance from the pulsed neutron source; and circuitry disposed in the tool body for controlling the pulsed neutron source, the monitor detector, and the at least one measurement detector.

Abstract: A rock classification system involves the use of a Ternary Diagram (TD) Model and a set of rules in a rule base. A computer, which stores a rock classification software which includes the rule base, will be responsive to certain data points from a Spectroscopy Sonde, will compare each data point with each of the rules in the rule base, and, when a match is found, will generate a specific rock classification for that data point. When a plurality of data points are input to the computer, a corresponding plurality of rock classifications are generated.

Abstract: A system for measuring density of material which can be embodied to measuring bulk density of material penetrated by a borehole. The probe component of the system comprises a source of neutron radiation and preferably two gamma ray spectrometers. The neutron source induces gamma radiation with energies up to about 10 MeV within the material being measured. Formation bulk density is determined by combining spectra of the induced gamma radiation with preferably two gamma ray spectrometers at differing axial spacings from the source. The high energy and dispersed nature of the induced gamma radiation yields greater radial depth of investigation than that obtainable with prior art backscatter density systems, which typically use gamma ray sources local to a probe and of energy about 1.3 MeV or less. The system can alternately be embodied to measure other material properties and to measure density of materials not penetrated by a borehole.

Abstract: A method for interpolating the environment and geological age at all levels in a borehole from information provided by a limited number of depths and the use of a synthetic stratigraphic cross-section for the interval between these depths. In hydrocarbon exploration, a borehole provides a suite of logs, plus estimates of geologic age at a number of spaced markers. This method uses a sea-level cycle chart, a calculation of subsidence from the thickness of the interval, and postulated values for several variables. If it is known that the supply of sediment always exceeded the available accommodation during deposition, the corresponding synthetic cross-section may then be optimized for geological plausibility (as gauged by visual observation or quantitative criteria) by perturbing the postulated variables and iterating the calculations.

Abstract: A method of estimating a petrophysical property of a subsurface area that includes deriving an acoustic calibration relationship correlating acoustic propagation characteristics of a first subsurface area with a petrophysical property of the first subsurface area determined using nuclear spectroscopy measurements; processing acoustic data acquired from a second subsurface area to determine acoustic propagation characteristics associated with a plurality of regions within the second subsurface area; and estimating the petrophysical property of the regions within the second subsurface area using the calibration relationship and the acoustic propagation characteristics associated with the second subsurface area.

Abstract: The invention relates to a borehole radar tool comprising, in a housing (2) a transmitting antenna and a receiving antenna both of which comprise, near the housing wall (2), a dipole antenna (8) and a reflector (10) opposite thereto. Also provided are an algorithm, method and apparatus for determining electromagnetic contrast information of a site into which electromagnetic fields (27) are emitted. Signals (29) generated by induction are intercepted and, using a back-projection algorithm including a suitable weighting factor, are converted into contrast information. The algorithm and/or method can be recorded in a computer program or on a data carrier. Also disclosed is a method of determining said weighting factor. The invention further provides a method and apparatus for subsurface surveys in which electromagnetic pulse signals are emitted.

Abstract: Measurements from many logging instruments such as Gamma ray counts from a pulsed neutron instrument, typically have a spectrum that contains a plurality of exponentially decaying components. The slowest decaying component is obtained by fitting a single exponential over the tail end of the data and selecting a beginning for the fitting window that minimizes the product of the chi-square and the standard error of the fit. The single determined component may be subtracted from the data and the process repeated to give additional components. The determined components are indicative of thermal neutron capture cross-sections.

Abstract: In the field of through-casing gas detection related to oil production there is a need to identify the presence of gas in a formation.

Abstract: System and method for characterizing formation properties based on NMR measurements. NMR clay measurements of this invention distinguish between interstitial pore water and the water adsorbed by the clay minerals. The measurements can be used to determine the quantity of adsorbed water in different clays and correct previously available data obtained using conventional density and neutron porosity logs. A new petrophysical parameter wetness clay is defined as an intrinsic parameter for clays, and its value is computed for members of the smectite group of clays, such as montmorillonite. The wet clay values for the density, neutron logs based on the adsorbed water in clays are used to enhance the quality and accuracy of the overall log interpretation.

Abstract: A method for interpolating the environment and geological age at all levels in a borehole from information provided by a limited number of depths and the use of a synthetic stratigraphic cross-section for the interval between these depths. In hydrocarbon exploration, a borehole provides a suite of logs, plus estimates of geologic age at a number of spaced markers. This method uses a sea-level cycle chart, a calculation of subsidence from the thickness of the interval, and postulated values for several variables. If it is known that the supply of sediment always exceeded the available accommodation during deposition, the corresponding synthetic cross-section may then be optimized for geological plausibility (as gauged by visual observation or quantitative criteria) by perturbing the postulated variables and iterating the calculations.

Abstract: A method for measuring one or more characteristics of an earth formation whereby energy is emitted circumferentially about a borehole into the formation, and the amount reflected back is detected during a plurality of sample periods. The samples are grouped into two or more groups by the azimuthal sector in which the sample was collected. Within a group, each sample is mathematically weighted according to the standoff of the detector from the borehole wall when the sample was taken. Within a group, the weighted samples are summed to produce a weighted total amount of energy detected within a sector. The weighted total is then transformed into the one or more characteristics.

Abstract: Measurements from many logging instruments such as Gamma ray counts from a pulsed neutron instrument, typically have a spectrum that contains a plurality of exponentially decaying components. The slowest decaying component is obtained by fitting a single exponential over the tail end of the data and selecting a beginning for the fitting window that minimizes the product of the chi-square and the standard error of the fit. The single determined component may be subtracted from the data and the process repeated to give additional components. The determined components are indicative of thermal neutron capture cross-sections.

Abstract: Methods are provided to quantitatively determine the separate amounts of oil and gas in a geological formation adjacent to a cased well using measurements of formation resistivity. The steps include obtaining resistivity measurements from within a cased well of a given formation, obtaining the porosity, obtaining the resistivity of formation water present, computing the combined amounts of oil and gas present using the Archie Relations, determining the relative amounts of oil and gas present, and then quantitatively determining the separate amounts of oil and gas present in the formation.

Abstract: Methods are disclosed for determining the standoff of a well logging instrument from the wall of a wellbore and the shape of the wellbore itself. The methods include measuring a compensated gamma-gamma formation density at a rotary orientation proximate a bottom of the wellbore, and measuring an apparent density at at least one other rotary orientation. The apparent density is related to the compensated density, a density of a fluid disposed between the logging instrument and a wall of the wellbore, and the standoff. Repeated measurements at a plurality of axial positions along the wellbore provide a log of the wellbore.

Abstract: A method for determing the potential in a three-dimensional domain containing a source domain of source particles and a target domain of target particles involves assigning the source particles into source particle clusters and the target particles into target particle clusters, assigning a collection point to each of the clusters, and determing the inverse distance from each particle to the collection point of its respective cluster. A pseudo-particle representative of each particle within the cluster is defined at the collection point of each cluster in accordance with the determined inverse distances and the charge-like measure of each of the particles. The potential, and/or its gradient, at any of the target particles is then determined from the position and the charge-like measure of the associated pseudo-particle.

Abstract: Method of detecting breaks in logging signals consisting of logs of different kinds recorded as a function of depth, of the type consisting in selecting a portion from each of the said logs in such a way that all the selected portions have a same depth interval in common, one of the selected portions being regarded as reference portion; selecting a parent wavelet function and constructing, from the said parent function, a family of wavelet analysis functions dependent on spatial frequency and on depth, the said method being characterized in that it furthermore consists in calculating, for each portion of log selected and for each depth datum, the absolute value of the mean gradient of the characteristic quantity of the wavelet transform for the various spatial analysis frequencies; selecting, for each portion of log processed, the peaks of the absolute value of the mean gradient of the characteristic quantity.

Abstract: A medical examination system, particularly a magnetic resonance system, has a host computer unit, a control computer unit and an image computer unit. The control computer unit is realized in the form of at least one insert card that is arranged in a commercially obtainable personal computer that contains the host computer unit.

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: A method of calibrating and using a radiation detector to quantify the radioactivity in or on a wide variety of objects, over a wide range of object sizes (points to hundreds of cubic meters), over a wide range of energies (e.g., 50-7000 keV photons), where the object can be at any location in a large sphere (e.g. 100 meter diameter) surrounding the detector, and where there can be various absorbers between the radioactive object and the detector (e.g., container, walls, air collimators), in which calibrations have been implemented and expanded following the method of Atrashkevich and Kolotov but without the use of radioactive sources and in minutes, and with no generation of radioactive waste. Such calibration technique can be applied to the quantiative analysis of a spectrum of radioactivity taken from a wide variety of in-situ or laboratory samples.

Abstract: Carbonate formations yield unreliable, down hole NMR results. Inter alia, these results must be corrected for temperature. The invention features several methods for obtaining more reliable NMR results for rock petrophysical parameters in carbonate rock formations based upon adjusting T.sub.2 data with respect to temperature.

Abstract: An integrated interpretation methodology is described that evaluates carbonate reservoirs. The methodology consists of first classifying the rock facies. A geometrical model specific to the classification is then used to predict the response of the rock to a variety of stimuli. A reconstruction of the geometrical model is made by comparing the measurements with the model predictions. The model is then used to predict the resistivity and the hydraulic transport properties of the rock, thereby enabling computation of both the reserves and their production behavior.

Abstract: An apparatus and method for measuring the size of a borehole while drilling are disclosed. The apparatus includes a gamma ray source configured to direct gamma rays into a formation, a far gamma ray detector and a near gamma ray detector configured to detect gamma rays originating in the formation and a far gamma ray counter and a near gamma ray counter coupled to the far gamma ray detector and the near gamma ray detector, respectively. The apparatus also includes a sampler coupled to the gamma ray counters configured to take and store samples from the counters, the sampler configured to reset the counter when a sample is taken. The apparatus includes a density computer for computing far density and near density for each sample, a standoff computer for computing the standoff for each sample from the far density for that sample, a formation density and a mud density, and a borehole size computer for adding the maximum standoff, the minimum standoff and the diameter of the apparatus.

Abstract: The present invention provides for method and an apparatus for determining the porosity of a geological formation surrounding a cased well. The method further comprises of generating neutron pulses that release neutrons into an area adjacent the well, from a neutron source. Neutrons are sensed and a plurality of neutron detector count rates is acquired using at least two neutron source to neutron detector spacings. A timing measurement is acquired at one of the spacings to measure a first depth of investigation. A ratio of the neutron detector count rates is acquired to measure a second depth of investigation. An apparent porosity is calculated using the timing measurements and the ratios of neutron count rates. The effect of a well casing on the calculated apparent porosity is determined in response to at least one of the ratio of neutron detector count rates and the timing measurement. A cement annulus is computed based on the ratios of neutron count rates and the timing measurement.

Abstract: Methods that allow in-situ calculations of critical petrophysical parameters including, but not limited to, .phi..sub.t, S.sub.xot, Q.sub.v, F, and R.sub.w are provided. Also, NMR clay bound water may be used to estimate a continuous Q.sub.v. In combination with other resistivity logs, such as SP, R.sub.xo and R.sub.deep, R.sub.w can be determined. With the exception of the saturation exponent n, all Archie parameters and other computational equivalents are continuously determined directly from well logs. The methods therefore allow S.sub.w to be determined more accurately, which leads to improved estimation of hydrocarbon reserves. The method is extended to complex lithology with additional tools. In complex lithology, permeability estimation is also improved using a method that estimates bound fluid volume. Also, an uncertainty analysis of the gas-corrected parameters is also provided.

Abstract: A method of determining a holdup value for a multiphase fluid. A first holdup component is calculated using a first detection technique which is insensitive to small inclusions of a first fluid constituent (hydrocarbons) dispersed in a second fluid constituent (water). A second holdup component is also calculated using a second detection technique which determines a percentage of the small inclusions of the first fluid constituent that are dispersed in the second fluid constituent. The first and second holdup components are then combined to yield a total holdup value. The method can further compensate for displacement of the second fluid constituent by the small inclusions of the first fluid constituent. The second holdup component is preferably calculated by inferring a maximum heavy phase density (MHPD) of the multiphase fluid.

Abstract: An apparatus and method for using swept frequency energy to inspect a casing or other body is disclosed. A transducer (75) transmits a swept frequency pulse at a casing and receives the reflection resulting from the pulse's impact against the casing. The reflected energy is translated to a reflection signal and analyzed by a signal processor having an envelope detector (240) which translates the reflection signal into an envelope signal. A microprocessor (260) located within the signal processor analyzes the envelope signal to compute data such as the thickness of the casing and the quality of the cement bond holding the casing.