Abstract: A subsurface logging tool that is deployable in a wellbore that traverses a formation includes a gamma-ray scintillation detector with a thallium-based scintillator material. The scintillator material is suitable for high-temperature downhole environments (i.e., above 70° C.). As such, the scintillator material improves the performance of oilfield measurement(s) at temperatures above 70° C. and at least up to 175° C., when compared with the use of the other materials. The scintillator material may have an effective atomic number of at least sixty. The scintillator material may have the chemical formula Tl2LiY1-xCexCl6, where x is 0 to 1. Lithium (Li) may be partially or completely replaced by another alkali metal or by indium (In). Yttrium (Y) is partially or completely replaced by another rare earth element. Chlorine (Cl) is partially or completely replaced by another halide.

Abstract: A subsurface logging tool that is deployable in a wellbore that traverses a formation includes a gamma-ray scintillation detector with a thallium-based scintillator material. The scintillator material is suitable for high-temperature downhole environments (i.e., above 70° C.). As such, the scintillator material improves the performance of oilfield measurement(s) at temperatures above 70° C. and at least up to 175° C., when compared with the use of the other materials. The scintillator material may have an effective atomic number of at least sixty. The scintillator material may have the chemical formula Tl2LiY1-xCexCl6, where x is 0 to 1. Lithium (Li) may be partially or completely replaced by another alkali metal or by indium (In). Yttrium (Y) is partially or completely replaced by another rare earth element. Chlorine (Cl) is partially or completely replaced by another halide.

Abstract: A method for estimating a borehole independent porosity of a subterranean formation includes processing a neutron logging data point, preferably including average near and far detector neutron count rates with suitable input data to obtain the porosity estimate. The borehole independent formation porosity may be obtained without any compensation and without any reliance on the measurement or estimation of sensor standoff and/or borehole caliper.

Abstract: A method for determining a bulk formation density using a neutron generator includes detected secondary gamma rays and evaluating the detected gamma rays according to pre-determined selection criteria. Selected gamma rays are then used to compute the formation density. The selection criteria may include, for example, a time delay between the detection of a neutron and an associated particle and/or a direction of propagation of the neutron.

Abstract: A well-logging tool may be positioned within a borehole of a subterranean formation. The well-logging tool may include a housing having an interior defining a dual-detector receiving chamber extending longitudinally, and having first and second portions, and a first azimuthal radiation detector carried by the first portion of the dual-detector receiving chamber. The first azimuthal radiation detector may include a first gamma-ray detector and a first photodetector associated with the first gamma-ray detector. The well-logging tool may include a second spectral radiation detector carried by the second portion of the dual-detector receiving chamber. The second spectral radiation detector may include a second gamma-ray detector and a second photodetector associated with the second gamma-ray detector.

Abstract: A well-logging tool may be positioned within a borehole of a subterranean formation. The well-logging tool may include a housing having an interior defining a dual-detector receiving chamber extending longitudinally, and having first and second portions, and a first azimuthal radiation detector carried by the first portion of the dual-detector receiving chamber. The first azimuthal radiation detector may include a first gamma-ray detector and a first photodetector associated with the first gamma-ray detector. The well-logging tool may include a second spectral radiation detector carried by the second portion of the dual-detector receiving chamber. The second spectral radiation detector may include a second gamma-ray detector and a second photodetector associated with the second gamma-ray detector.

Abstract: A well-logging tool may be positioned within a borehole of a subterranean formation. The well-logging tool may include a housing having an interior defining a dual-detector receiving chamber extending longitudinally, and having first and second portions, and a first azimuthal radiation detector carried by the first portion of the dual-detector receiving chamber. The first azimuthal radiation detector may include a first gamma-ray detector and a first photodetector associated with the first gamma-ray detector. The well-logging tool may include a second azimuthal radiation detector carried by the second portion of the dual-detector receiving chamber. The second azimuthal radiation detector may include a second gamma-ray detector and a second photodetector associated with the second gamma-ray detector.

Abstract: A neutron logging tool includes a neutron source and at least one position sensitive thermal or epithermal neutron detector. The logging tool further includes an electronic controller configured to estimate the axial location of detected neutrons. Measurement of the axial neutron flux distribution enables other formation and borehole parameters such as formation porosity and sensor standoff to be computed. In logging while drilling embodiments, a borehole caliper may also be computed form the axial neutron flux distribution.

Abstract: A method for determining a bulk formation density using a neutron generator includes detected secondary gamma rays and evaluating the detected gamma rays according to pre-determined selection criteria. Selected gamma rays are then used to compute the formation density. The selection criteria may include, for example, a time delay between the detection of a neutron and an associated particle and/or a direction of propagation of the neutron.

Abstract: A method for estimating a borehole independent porosity of a subterranean formation includes processing a neutron logging data point, preferably including average near and far detector neutron count rates with suitable input data to obtain the porosity estimate. The borehole independent formation porosity may be obtained without any compensation and without any reliance on the measurement or estimation of sensor standoff and/or borehole caliper.

Abstract: The downhole tool disclosed herein comprises a body, a flexible member attached to the body, and a transducer housed in the body. The flexible member compresses against one side of the wellbore and urges the body against the other side. The transducer emits a signal to the flexible member reflectable from the flexible member back to the transducer. The signal travel time from the transducer to the flexible member and back is analyzed for estimating the distance between the body and the flexible member. The standoff distance can be estimated from the distance between the body and the flexible member. From the standoff distance, the wellbore diameter is estimated. The tool may also obtain wellbore dimensions by obtaining near side wellbore standoff and using a magnetic ruler to determine bowspring flexing. The magnetic ruler results may be used in conjunction with or without the far side standoff data.

Abstract: A neutron logging tool includes a neutron source and at least one position sensitive thermal or epithermal neutron detector. The logging tool further includes an electronic controller configured to estimate the axial location of detected neutrons. Measurement of the axial neutron flux distribution enables other formation and borehole parameters such as formation porosity and sensor standoff to be computed. In logging while drilling embodiments, a borehole caliper may also be computed form the axial neutron flux distribution.

Abstract: A photoelectric factor (PEF) that is corrected for standoff effects is obtained from measurements made with a single detector. A first PEF is obtained using a first pair of soft and hard windows and a second PEF is obtained using a second pair of soft and hard windows. Additional correction to the PEF may be made using a formation density measured by the logging tool.

Abstract: The downhole tool disclosed herein comprises a body, a flexible member attached to the body, and a transducer housed in the body. The flexible member compresses against one side of the wellbore and urges the body against the other side. The transducer emits a signal to the flexible member reflectable from the flexible member back to the transducer. The signal travel time from the transducer to the flexible member and back is analyzed for estimating the distance between the body and the flexible member. The standoff distance can be estimated from the distance between the body and the flexible member. From the standoff distance, the wellbore diameter is estimated. The tool may also obtain wellbore dimensions by obtaining near side wellbore standoff and using a magnetic ruler to determine bowspring flexing. The magnetic ruler results may be used in conjunction with or without the far side standoff data.

Abstract: A photoelectric factor (PEF) that is corrected for standoff effects is obtained from measurements made with a single detector. A first PEF is obtained using a first pair of soft and hard windows and a second PEF is obtained using a second pair of soft and hard windows. Additional correction to the PEF may be made using a formation density measured by the logging tool. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.

Abstract: A tool is presented for making density measurements of a formation surrounding a wellbore, comprising a collar housing in a drill string. The housing has at least one first section with a first outer diameter, and at least one sensing section with a second outer diameter located proximate the at least one first section. The second outer diameter is smaller than the first outer diameter. A radioactive source is disposed in the sensing section of the housing. At least two detectors are disposed in the sensing section and spaced from the radioactive source and are positioned to detect radiation resulting from gamma rays emitted by the source.

Abstract: A tool for measuring formation properties in situ. The tool includes a solid state neutron detector and a neutron source disposed on a drill string or wireline. The detector includes a boron carbon surface deposited on a substrate, and the surface can be multi-planar or curved for allowing sensitivity in more than one direction.

Abstract: A tool is presented for making density measurements of a formation surrounding a wellbore, comprising a collar housing in a drill string. The housing has at least one first section with a first outer diameter, and at least one sensing section with a second outer diameter located proximate the at least one first section. The second outer diameter is smaller than the first outer diameter. A radioactive source is disposed in the sensing section of the housing. At least two detectors are disposed in the sensing section and spaced from the radioactive source and are positioned to detect radiation resulting from gamma rays emitted by the source.

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.