Abstract: An apparatus for use in acoustically assessing a wellbore, comprises a tubular body, an acoustic transmitter supported on the body, first and second acoustic receivers supported on the body with the second receiver being farther from the transmitter, wherein at least one of the inner and outer body surfaces includes a helical groove between the acoustic transmitter and the first acoustic receiver and the helical groove is filled with a composite material. The body may include a second helical groove that has the same pitch as the first helical groove and is diametrically opposite the first helical groove and may further include a third helical groove between the first and second receivers. At least one of the grooves may an opening width that is less than the maximum groove width and may have a cross-sectional area that includes a neck. The composite material may comprise tungsten particles in rubber.

Abstract: A method for adjusting a gain of a gamma detector comprises detecting gamma radiation using the detector, recording the detected radiation as count rates in channels, wherein the last channel accumulates all counts above the maximum recorded energy; comparing the last channel count rate (LCCR) to a threshold X and, if LCCR>X, decreasing the gain by a preset amount Y. If LCCR?X, establishing a first estimate of a needed voltage HV1 using tool temperature and a temperature lookup table, and establishing a second estimate of a needed voltage HV2 using a backscatter peak value and a backscatter lookup table; comparing |HV1?HV2| to a threshold Z; if |HV1?HV2|<Z, adjusting the gain of the gamma detector by HV2 or, if |HV1?HV2|?Z, adjusting the gain of the gamma detector by HV1.

Abstract: A method for adjusting a gain of a gamma detector comprises detecting gamma radiation using the detector, recording the detected radiation as count rates in channels, wherein the last channel accumulates all counts above the maximum recorded energy; comparing the last channel count rate (LCCR) to a threshold X and, if LCCR>X, decreasing the gain by a preset amount Y. If LCCR?X, establishing a first estimate of a needed voltage HV1 using tool temperature and a temperature lookup table, and establishing a second estimate of a needed voltage HV2 using a backscatter peak value and a backscatter lookup table; comparing |HV1?HV2| to a threshold Z; if |HV1?HV2|<Z, adjusting the gain of the gamma detector by HV2 or, if |HV1?HV2|?Z, adjusting the gain of the gamma detector by HV1.

Abstract: An apparatus for use in acoustically assessing a wellbore, comprises a tubular body, an acoustic transmitter supported on the body, first and second acoustic receivers supported on the body with the second receiver being farther from the transmitter, wherein at least one of the inner and outer body surfaces includes a helical groove between the acoustic transmitter and the first acoustic receiver and the helical groove is filled with a composite material. The body may include a second helical groove that has the same pitch as the first helical groove and is diametrically opposite the first helical groove and may further include a third helical groove between the first and second receivers. At least one of the grooves may an opening width that is less than the maximum groove width and may have a cross-sectional area that includes a neck. The composite material may comprise tungsten particles in rubber.

Abstract: A downhole assembly includes a drill collar, the drill collar having an outer wall and an insert, the insert positioned within drill collar. The insert has a bore therethrough. The downhole assembly further includes at least one sensor within the insert, wherein the sensor is a gamma ray detector.

Abstract: Prior to actual use in a downhole application, gamma spectrum shape for a gamma detector can be quantified, and a relationship established between detector gain and spectrum shape. Given this relationship, the shape of a gamma spectrum measured after downhole deployment of the detector within a wellbore, for example as part of a tool in a drill string, can be quantified and compared to the pre-established relationship to determine whether the detector gain has drifted due to temperature or operating time effects. Using this relationship, a gain-affecting voltage across the detector (e.g., the photocathode voltage across the photomultiplier tube) can be adjusted to compensate for such drifts and thus to compensate for variations caused by temperature or operating time. With such compensation applied to the detector, resulting gamma spectra reliably indicate actual differences in radiation levels, thus enabling an inference of the composition of the formation at various times/depths.

Abstract: A downhole assembly includes a drill collar, the drill collar having an outer wall and an insert, the insert positioned within drill collar. The insert has a bore therethrough. The downhole assembly further includes at least one sensor within the insert, wherein the sensor is a gamma ray detector.

Abstract: Prior to actual use in a downhole application, gamma spectrum shape for a gamma detector can be quantified, and a relationship established between detector gain and spectrum shape. Given this relationship, the shape of a gamma spectrum measured after downhole deployment of the detector within a wellbore, for example as part of a tool in a drill string, can be quantified and compared to the pre-established relationship to determine whether the detector gain has drifted due to temperature or operating time effects. Using this relationship, a gain-affecting voltage across the detector (e.g., the photocathode voltage across the photomultiplier tube) can be adjusted to compensate for such drifts and thus to compensate for variations caused by temperature or operating time. With such compensation applied to the detector, resulting gamma spectra reliably indicate actual differences in radiation levels, thus enabling an inference of the composition of the formation at various times/depths.

Abstract: Prior to actual use in a downhole application, gamma spectrum shape for a gamma detector can be quantified, and a relationship established between detector gain and spectrum shape. Given this relationship, the shape of a gamma spectrum measured after downhole deployment of the detector within a wellbore, for example as part of a tool in a drill string, can be quantified and compared to the pre-established relationship to determine whether the detector gain has drifted due to temperature or operating time effects. Using this relationship, a gain-affecting voltage across the detector (e.g., the photocathode voltage across the photomultiplier tube) can be adjusted to compensate for such drifts and thus to compensate for variations caused by temperature or operating time. With such compensation applied to the detector, resulting gamma spectra reliably indicate actual differences in radiation levels, thus enabling an inference of the composition of the formation at various times/depths.

Abstract: Prior to actual use in a downhole application, gamma spectrum shape for a gamma detector can be quantified, and a relationship established between detector gain and spectrum shape. Given this relationship, the shape of a gamma spectrum measured after downhole deployment of the detector within a wellbore, for example as part of a tool in a drill string, can be quantified and compared to the pre-established relationship to determine whether the detector gain has drifted due to temperature or operating time effects. Using this relationship, a gain-affecting voltage across the detector (e.g., the photocathode voltage across the photomultiplier tube) can be adjusted to compensate for such drifts and thus to compensate for variations caused by temperature or operating time. With such compensation applied to the detector, resulting gamma spectra reliably indicate actual differences in radiation levels, thus enabling an inference of the composition of the formation at various times/depths.

Abstract: Acoustic data acquired in a MWD/LWD system can be compressed for transmission to the surface. The compression technique can include semblance processing acoustic signals received at a plurality of receivers spaced apart from a transmitter to generate a semblance projection at each of a plurality of depths. Peaks of the semblance projection can then be telemetered to the surface, with each peak including a slowness (velocity) value and a coherence (semblance) value. The telemetered values may be processed at the surface to generate logs as a function of depth.

Abstract: Acoustic data acquired in a MWD/LWD system can be compressed for transmission to the surface. The compression technique can include semblance processing acoustic signals received at a plurality of receivers spaced apart from a transmitter to generate a semblance projection at each of a plurality of depths. Peaks of the semblance projection can then be telemetered to the surface, with each peak including a slowness (velocity) value and a coherence (semblance) value. The telemetered values may be processed at the surface to generate logs as a function of depth.

Abstract: Apparatus and methods for measuring gamma ray energy spectra wherein the gain of the measurement system is continuously and automatically adjusted to a standard gain. Gain of the system is controlled automatically through analysis of the measured energy spectra. Alternately, the gain of the system is controlled by the use of a calibration source and the operation of the system at a standard and amplified gain. Gain control can be improved further by combining both the spectral analysis and calibration source methodology. The system can be embodied in a wireline or logging-while-drilling borehole logging systems that measure naturally occurring or induced gamma ray spectra. The system can also be used in non-borehole applications including non-borehole gamma ray spectral systems such as computer-aided-tomography scan systems, security scanning systems, radiation monitoring systems, process control systems, analytical measurement systems using activation analysis methodology, and the like.

Abstract: A logging system for measuring parameters of earth formation penetrated by a well borehole. Measurements made with the system are not adversely affected by varying pressure encountered a borehole environment. This is accomplished by the use of a main compensation element and a detector compensation element to render source and detector geometry invariant to varying pressure. The system is particularly suited for nuclear LWD systems such as back scatter gamma ray density systems. The basic concepts of the system are, however, applicable to other types of nuclear measurement systems that comprise one or more radiation sources, and one or more axially spaced radiation detectors, where system response is a function of source-detector spacing. The basic concepts of the system are also applicable to other types of logging systems, such as electromagnetic and acoustic, where source (transmitter) and sensor (receiver) elements require invariant geometry in order to maximize accuracy of measurements.

Abstract: A logging system for measuring parameters of earth formation penetrated by a well borehole. Measurements made with the system are not adversely affected by varying pressure encountered a borehole environment. This is accomplished by the use of a main compensation element and a detector compensation element render source and detector geometry invariant to varying pressure. The system is particularly suited for nuclear LWD systems such as back scatter gamma ray density systems. The basic concepts of the system are, however, applicable to other types of nuclear measurement systems that comprise one or more radiation sources, and one or more axially spaced radiation detectors, where system response is a function of source-detector spacing. The basic concepts of the system are also applicable to other types of logging systems, such as electromagnetic and acoustic, where source (transmitter) and sensor (receiver) elements require invariant geometry in order to maximize accuracy of measurements.

Abstract: Apparatus and methods for measuring gamma ray energy spectra wherein the gain of the measurement system is continuously and automatically adjusted to a standard gain. Gain of the system is controlled automatically through analysis of the measured energy spectra. Alternately, the gain of the system is controlled by the use of a calibration source and the operation of the system at a standard and amplified gain. Gain control can be improved further by combining both the spectral analysis and calibration source methodology. The system can be embodied in a wireline or logging-while-drilling borehole logging systems that measure naturally occurring or induced gamma ray spectra. The system can also be used in non-borehole applications including non-borehole gamma ray spectral systems such as computer-aided-tomography scan systems, security scanning systems, radiation monitoring systems, process control systems, analytical measurement systems using activation analysis methodology, and the like.

Abstract: A method for determining concentrations of naturally occurring radioactive elements in earth formation by analysis of gamma ray energy spectra measured by at least one gamma ray detector while the borehole is being drilled. Gain of the gamma ray detector is controlled automatically through analysis of the spectra. The one or more gamma ray detectors are disposed at the periphery of the downhole instrumentation to maximize sensitivity. Elemental concentrations of naturally occurring radioactive elements such as potassium, uranium and thorium are measured either as a function of depth in the borehole, or as a function of aximuthal sectors around the borehole wall, or as a function of both depth and azimuthal sectors.

Abstract: A system for measuring elemental compositions and other properties of earth formation penetrated by a borehole, wherein the measurements are made while drilling the borehole. The downhole instrumentation includes a neutron source and a gamma ray detector disposed in a drill collar. Formation parameters of interest are determined from the energy and intensity of gamma radiation induced in the formation by the neutron source. By minimizing the amount of iron in the immediate vicinity of the gamma ray detector, disposing no iron directly between the detector and the formation, and positioning the gamma ray detector as close as practical to the formation, interfering gamma radiation from iron is reduced thereby increasing precision and accuracy of the formation parameter measurements.

Abstract: A system for measuring elemental compositions and other properties of earth formation penetrated by a borehole, wherein the measurements are made while drilling the borehole. The downhole instrumentation includes a neutron source and a gamma ray detector disposed in a drill collar. Formation parameters of interest are determined from the energy and intensity of gamma radiation induced in the formation by the neutron source. By minimizing the amount of iron in the immediate vicinity of the gamma ray detector, disposing no iron directly between the detector and the formation, and positioning the gamma ray detector as close as practical to the formation, interfering gamma radiation from iron is reduced thereby increasing precision and accuracy of the formation parameter measurements.