Abstract: An apparatus for detecting thermal and epithermal neutrons. The apparatus includes a first radiation responsive element configured to absorb substantially all incident thermal neutrons and produce first light scintillations indicative of the absorbed thermal neutrons and a second radiation responsive element configured to produce second light scintillations indicative of at least epithermal neutrons that traverse the first radiation responsive element. Also disclosed are borehole logging methods and apparatuses for estimating formation properties using nuclear radiation, particularly an apparatus and method for estimating parameters of a formation. The method may include using neutron count rate information from a detector to model porosity or salinity. The apparatus includes a processor and storage subsystem with a program that, when executed, implements the method.

Abstract: In one aspect, a method of making a drill bit is disclosed that includes selecting a drill bit configuration, obtaining a stress map for the drill bit configuration relating to a drilling operation, performing a mechanical test with an actual drill bit having the selected configuration, and selecting a location on a surface of the drill bit for installing a sensor thereat based on a location of low stress from the stress map and results of the mechanical test, and placing a sensor at the selected location.

Abstract: The present disclosure relates to borehole logging methods and apparatuses for estimating formation properties using nuclear radiation, particularly an apparatus and method for estimating amounts of silicon and/or oxygen in the formation using exposure time information. The method may include using nuclear radiation information from at least one nuclear radiation detector to estimate at least one parameter of interest. The method may also include reducing an error in the estimated formation properties due to speed variations of a nuclear radiation source that activates the silicon and oxygen in the formation. The apparatus may include at least one nuclear radiation detector. The apparatuses may include an information processing device to perform the methods.

Abstract: Methods of evaluating a parameter of interest of a formation intersected by a borehole, including exposing a radiation sensor in the borehole to a calibration radiation source while a measurement operation using the radiation sensor is suspended. Methods may include exposing the radiation sensor to the calibration radiation source when the radiation sensor is stationary relative to the formation or during interruption of drilling operations or at predetermined intervals; processing response information, including performing a mitigation process on a portion of the response information relating to exposure of the radiation sensor to a calibration radiation source during measurement operations; or using the calibrated measurement information to estimate parameters of interest. Devices may include a radiation sensor, a calibrator including a calibration radiation source, and an actuator configured to intermittently expose the radiation sensor to the calibration radiation source.

Abstract: An apparatus for estimating porosities of a formation includes: a borehole conveyable pulsed neutron generator to emit a pulse of high energy neutrons; a short spaced neutron detector to provide a count rate as a function of time; a long spaced neutron detector to provide a count rate as a function of time; a timing gate to synchronize a timing of neutrons detected by the detectors with respect to the neutron pulse; and a processor. The processor is configured to determine epithermal count rates and thermal count rates for the detectors based on timing of detection of neutrons with respect to the neutron pulse and calculate a first ratio of short to long spaced detector epithermal count rates and a second ratio of short to long spaced detector thermal count rates. The processor estimates an epithermal porosity using the first ratio and a thermal porosity using the second ratio.

Abstract: A method of estimating at least one property of an earth formation includes: constructing a matrix model of a formation; constructing a shale model of the formation, the shale model including an estimation of a concentration of at least one trace element; combining the first model and the second model to generate a formation model; and comparing measured pulsed neutron data with the mixed model to estimate the at least one property.

Abstract: Methods, systems, devices, and products for estimating a parameter of interest of a volume of an earth formation. Methods may include correcting a measurement relating to the parameter of interest by a downhole tool using at least one correction model determined from a plurality of predefined models. The at least one correction model may be determined based on an estimated borehole standoff of the tool from the borehole wall that is associated with the measurement. Correcting the measurement may include determining a correction factor using the correction model and applying the correction factor to the measurement. Each of the plurality of predefined models may be associated with each of a plurality of standoff bins, wherein each of the plurality of standoff bins is defined as a mutually exclusive interval of distance values from the downhole tool to the borehole wall.

Abstract: A method of estimating fluid composition in an earth formation includes: generating at least one pulsed neutron measurement by a pulsed neutron tool; estimating a pulsed neutron fluid saturation by analyzing the at least one pulsed neutron measurement via a pulsed neutron model of the earth formation, the pulsed neutron model including expected pulsed neutron measurements relative to selected fluid composition and properties; comparing the pulsed neutron fluid saturation to a reference fluid saturation estimated via a downhole tool; adjusting the pulsed neutron model to at least substantially eliminate a difference between the pulsed neutron fluid saturation and the reference fluid saturation by adjusting at least one of the selected fluid composition and the selected fluid properties; and estimating at least one of the fluid composition and the fluid properties based on the adjusted model.

Abstract: Methods, systems, devices, and products for estimating at least one parameter of interest of a volume of an earth formation, including density, porosity, and fluid saturation of the volume. Methods may include normalizing radiation information relating to radiation emissions from a spatially distributed nuclear source and indicative of a property of the earth volume using a correction factor determined using an estimated lithology of the volume. The nuclear source may be in the volume. Radiation emissions may be generated by neutron irradiation of at least one nuclide in the volume. The correction factor may be determined using any of nuclear density of the at least one nuclide; an estimated concentration of the at least one nuclide in the volume; or a parameter relating to concentration of the nuclide in the volume. The emissions may include gamma rays.

Abstract: An apparatus and method for estimating at least one parameter of interest of an earth formation including an estimation of the parameter of interest using a time-dependent ratio of information obtained from at least one neutron detector through the exposure of the earth formation to a radiation source, particularly a pulsed nuclear source. The apparatus includes a processor and storage subsystem with a program that, when executed, implements the method. Also, an apparatus and method for estimating at least one parameter of interest of an earth formation including an estimation of the parameter of interest using a first component and a second component of an information set obtained using a single radiation detector.

Abstract: A drill bit made according to one embodiment includes a source configured to induce radiation into a formation during drilling of a wellbore and a sensor in the drill bit configured to detect radiation from the formation responsive to the radiation induced by the source. The drill bit may further include a circuit configured to process signals received from the sensor to estimate a property of the formation.

Abstract: An apparatus for detecting thermal and epithermal neutrons. The apparatus includes a first radiation responsive element configured to absorb substantially all incident thermal neutrons and produce first light scintillations indicative of the absorbed thermal neutrons and a second radiation responsive element configured to produce second light scintillations indicative of at least epithermal neutrons that traverse the first radiation responsive element. Also disclosed are borehole logging methods and apparatuses for estimating formation properties using nuclear radiation, particularly an apparatus and method for estimating parameters of a formation. The method may include using neutron count rate information from a detector to model porosity or salinity. The apparatus includes a processor and storage subsystem with a program that, when executed, implements the method.

Abstract: A method for estimating a property of an earth formation, the method includes: conveying a carrier through a borehole penetrating the earth formation; irradiating the formation with neutrons from a neutron source disposed at the carrier; detecting a first signal from the formation due to the irradiating using a first radiation detector, the first signal being related to a saturation of a fluid in the formation; detecting a second signal from an element in the formation due to the irradiating using a second radiation detector, the second signal being related to an element emitting the second signal in the formation; and estimating the property from the first signal and the second signal.

Abstract: A method for estimating a parameter of interest of an earth formation having a fluid contained in pores of the earth formation, the method includes: conveying a carrier through a borehole penetrating the earth formation; irradiating the earth formation with neutrons from a neutron source disposed at the carrier; measuring radiation emitted from the earth formation resulting from the irradiating using at least one detector; calculating or determining a mathematical parameter from radiation measured by the at least one detector; predicting values of the mathematical parameter over a range of values of an earth formation property; and comparing the mathematical parameter to the predicted values to estimate the parameter of interest.

Abstract: In one aspect, the present disclosure provides an apparatus for determining formation density. One embodiment of the apparatus includes a bottomhole assembly having a drill bit attached to end thereof for drilling through a formation, a first sensor in the drill bit configured to provide first signals for determining a first density of the formation proximate to the drill, a second sensor distal from the first sensor configured to provide signals for determining density of a second density of the formation, and a processor configured to determine the formation density from the first density and the second density.

Abstract: A method for estimating a concentration of carbon dioxide (CO2) in a formation penetrated by a borehole, the method includes: conveying a carrier through the borehole; irradiating the formation with neutrons from a neutron source disposed at the carrier; detecting photons from the formation resulting from the irradiating; and estimating the concentration of CO2 from data acquired from the detecting.

Abstract: An instrument for performing measurements downhole, includes an irradiator oriented to irradiate sub-surface materials surrounding the instrument, the irradiator including at least one neutron source disposed proximate to a moderator for providing a source of inelastic gamma photons and also disposed proximate to a material for providing a source of capture gamma photons; and a first detector and a second detector, each detector for detecting gamma rays and oriented in a relationship to the irradiator for receiving gamma photons from at least one of the irradiator and the formation. A method for irradiating sub-surface materials is provided.

Abstract: A method for performing a measurement of a property downhole includes: using an instrument including an irradiator including a pulsed neutron generator, a moderator and a material including a high cross section for capturing thermal neutrons downhole, generating inelastic gamma photons from neutron interactions in the moderator and generating capture gamma photons from neutron interactions in the material; irradiating sub-surface materials proximate to the instrument with the inelastic gamma photons and the capture gamma photons; detecting radiation scattered by the sub-surface materials; and estimating the property according to the detected radiation. A system is also disclosed.

Abstract: In one aspect, a method of making a drill bit is disclosed that includes selecting a drill bit configuration, obtaining a stress map for the drill bit configuration relating to a drilling operation, performing a mechanical test with an actual drill bit having the selected configuration, and selecting a location on a surface of the drill bit for installing a sensor thereat based on a location of low stress from the stress map and results of the mechanical test, and placing a sensor at the selected location.

Abstract: In one aspect, the present disclosure provides an apparatus for determining formation density. One embodiment of the apparatus includes a bottomhole assembly having a drill bit attached to end thereof for drilling through a formation, a first sensor in the drill bit configured to provide first signals for determining a first density of the formation proximate to the drill, a second sensor distal from the first sensor configured to provide signals for determining density of a second density of the formation, and a processor configured to determine the formation density from the first density and the second density.