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: A method of calculating a porosity of a geological formation includes determining a bulk pore volume and a movable fluid pore volume in the geological formation in which drilling mud including a mud filtrate is introduced, calculating a porosity of the formation based on a bulk pore volume, and correcting the porosity based on the movable fluid volume in the geological formation.

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: 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 of calculating a porosity of a geological formation includes determining a bulk pore volume and a movable fluid pore volume in the geological formation in which drilling mud including a mud filtrate is introduced, calculating a porosity of the formation based on a bulk pore volume, and correcting the porosity based on the movable fluid volume in the geological formation.

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: 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: 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: A method for estimating information about a formation, the method including obtaining a first set of radiation data substantially influenced by the formation and non-formation materials; obtaining a second set of radiation data substantially influenced by the non-formation materials; and correcting the first set of radiation data with the second set of radiation data to provide corrected formation radiation data.

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: A method for estimating information about a formation, the method including obtaining a first set of radiation data substantially influenced by the formation and non-formation materials; obtaining a second set of radiation data substantially influenced by the non-formation materials; and correcting the first set of radiation data with the second set of radiation data to provide corrected formation radiation data.

Abstract: A method for measuring radiation, the method includes selecting at least two radiation detectors, each detector having a spatial resolution that differs from the spatial resolution of other detectors; measuring the radiation with the detectors; and combining a response from at least two of the detectors to produce a composite response exhibiting a spatial resolution.