The disclosure provides a well integrity monitoring tool for a wellbore, a method, using a nuclear tool and an EM tool, for well integrity monitoring of a wellbore having a multi-pipe configuration, and a well integrity monitoring system. In one example, the method includes: operating a nuclear tool in the wellbore to make a nuclear measurement at a depth of the wellbore, operating an EM tool in the wellbore to make an EM measurement at the depth of the wellbore, determining a plurality of piping properties of the multi-pipe configuration at the depth employing the EM measurement, determining, employing the piping properties, a processed nuclear measurement from the nuclear measurement, and employing the processed nuclear measurement to determine an integrity of a well material at the depth and within an annulus defined by the multi-pipe configuration.

Methods and apparatus for estimating parameters of interest of a volume in an earth formation from a response spectrum representing radiation information obtained by a radiation detector in a borehole intersecting the volume responsive to nuclear phenomena in the volume, the response spectrum including spectral distortion resulting i) environmental conditions in the formation, or ii) deterioration of at least one component of the radiation detector. Methods include recovering an enhanced response spectrum estimating the true spectrum, comprising mitigating the spectral distortion by applying at least one contrast sharpening mask to the response spectrum. The at least one contrast sharpening mask may comprise at least a low pass smoothing mask subtracted from a unity mask which when applied to the response spectrum obtains high-frequency data and adds the high-frequency data to the response spectrum. The response spectrum may be a gamma ray spectrum.

A variety of applications can include a gamma ray downhole logging system having a gamma ray detector, where temperature sensitivity of the gamma ray detector is accounted for in the operation of the logging system. Correction of sensitivity of the gamma ray detector can include using a measure of sensitivity drift derived from temperature binned gamma ray spectra from measurements by the gamma ray detector over a calibration period for a number of calibration periods. Additional apparatus, systems, and methods are disclosed.

A method includes introducing a tool string into a wellbore having annular material disposed in an annulus defined between casing and the wellbore. Obtaining acoustic refracted waveform measurements of the annular material from a cement bond logging tool, obtaining ultrasonic measurements of the annular material from a circumferential acoustic scanning tool, obtaining gamma radiation measurements scattered from the annular material from a spectral density logging tool, and obtaining thermal neutron radiation measurements scattered from the annular material from a dual spaced neutron logging tool. Obtained measurements may then be collected and computed with a computer and a deliverable is generated that includes one or more cross plots providing a compositional equivalent of the annular material.

A method includes introducing a tool string into a wellbore having annular material disposed in an annulus defined between casing and the wellbore. Obtaining acoustic refracted waveform measurements of the annular material from a cement bond logging tool, obtaining ultrasonic measurements of the annular material from a circumferential acoustic scanning tool, obtaining gamma radiation measurements scattered from the annular material from a spectral density logging tool, and obtaining thermal neutron radiation measurements scattered from the annular material from a dual spaced neutron logging tool. Obtained measurements may then be collected and computed with a computer and a deliverable is generated that includes one or more cross plots providing a compositional equivalent of the annular material.

A wellbore inspection apparatus and a corresponding method of operation are described. The wellbore inspection apparatus comprises a neutron generator that produces, by a fusion reaction, a neutron and a corresponding charged particle. An associated particle imaging (API) detector comprises a particle detector array that detects the corresponding charged particle. The particle detector array comprises a plurality of particle detector elements that facilitate determining a trajectory of the neutron based upon a detection, by a particular one of the plurality of particle detector elements, of the corresponding charged particle. A gamma-ray detector assembly comprises a set of gamma-ray detector elements, and a set of collimating structures, where adjacent pairs of the set of collimating structures define a gamma-ray path for a gamma-ray arising from an inelastic collision of the neutron.

A borehole neutron imaging tool having a two-dimensional array of neutron detector crystals, wherein said tool includes at least a source of neutrons; at least one collimated imaging detector to record images created by incident neutrons; sonde-dependent electronics; and a plurality of tool logic electronics and power supply units. A method for borehole neutron imaging, the method including controlling the direction of incident neutrons onto the imaging array; imaging said borehole surroundings; and creating a composite image of the materials surrounding the formation.

A borehole neutron imaging tool having a two-dimensional array of neutron detector crystals, wherein said tool includes at least a source of neutrons; at least one collimated imaging detector to record images created by incident neutrons; sonde-dependent electronics; and a plurality of tool logic electronics and power supply units. A method for borehole neutron imaging, the method including controlling the direction of incident neutrons onto the imaging array; imaging said borehole surroundings; and creating a composite image of the materials surrounding the formation.

Methods and apparatus for estimating parameters of interest of a volume in an earth formation from a response spectrum representing radiation information obtained by a radiation detector in a borehole intersecting the volume responsive to nuclear phenomena in the volume, the response spectrum including spectral distortion resulting i) environmental conditions in the formation, or ii) deterioration of at least one component of the radiation detector. Methods include recovering an enhanced response spectrum estimating the true spectrum, comprising mitigating the spectral distortion by applying at least one contrast sharpening mask to the response spectrum. The at least one contrast sharpening mask may comprise at least a low pass smoothing mask subtracted from a unity mask which when applied to the response spectrum obtains high-frequency data and adds the high-frequency data to the response spectrum. The response spectrum may be a gamma ray spectrum.

A first set of radiation detectors may be disposable on the a drill string, wherein the first set of radiation detectors are capable of detecting gamma radiation and neutron radiation; and a combined chemical source spaced from the first set of radiation detectors, wherein the combined chemical source comprises a gamma radiation emitting material and a neutron radiation emitting material. The first set of radiation detectors and combined chemical source may be used in methods for logging a wellbore.