Abstract: A downhole tool for acoustically imaging a subterranean formation having a transmitter and receiver and which includes an acoustic isolator between the transmitter and receiver. The acoustic isolator includes attenuation elements with rounded ends and that are connected in series by compression fittings. The compression fittings include sleeves that threadingly engage lock nuts and compressively engage the rounded ends. The contact interfaces between the compression fittings extend along a curved path thereby limiting acoustic transmission along the series of attenuation elements.

Abstract: Monitoring scattered gamma rays is used to identify substances disposed between coaxial tubulars disposed in a subterranean wellbore. Gamma rays are strategically directed from within an inner most tubular and into the annulus, some of the gamma rays scatter from the substance between the tubulars and are detected with detectors set a designated axial distance from the gamma ray source. Gamma rays also scatter from fluid within the tubular, a ratio of the gamma rays detected that scatter from the fluid in the tubular and from the substance can be used to determine the substance.

Abstract: A logging system for imaging a subterranean formation that includes radiation sources that emit different energy levels of radiation into the formation. The radiation scatters from the formation and is sensed by a single sensor that is responsive to the different energy levels of radiation. The single sensor includes a crystal which includes cesium, lithium, yttrium, cerium, and chlorine. The radiation sources emit neutron rays and gamma rays.

Abstract: A downhole tool for acoustically imaging a subterranean formation having a transmitter and receiver and which includes an acoustic isolator between the transmitter and receiver. The acoustic isolator includes attenuation elements with rounded ends and that are connected in series by compression fittings. The compression fittings include sleeves that threadingly engage lock nuts and compressively engage the rounded ends. The contact interfaces between the compression fittings extend along a curved path thereby limiting acoustic transmission along the series of attenuation elements.

Abstract: A well logging system that includes a tool which is deployed within the well. The tool has a housing in which imaging hardware is stored, and on which sensors are located, where the sensors detect and measure electrical signals that have been induced in the formation surrounding the well. A wiper system is also mounted on the housing for clearing mud and other debris from outer surfaces of the sensors.

Abstract: A downhole string and method of operating where tension in the downhole string is monitored real time so that the tension in the downhole string does not exceed its yield strength. Included with the string is a tension sub for monitoring the tension that includes a sensor in the housing of the tension sub. The sensor can be a strain gauge and can be placed proximate an upper end of the downhole string so that tension in a wireline attached to the string can also be monitored. The portion of the housing having the sensor is narrowed for enhancing sensitivity of monitoring.

Abstract: Substances on or adjacent a tubular disposed in a subterranean wellbore can be detected and/or their presence identified by monitoring gamma rays scattered from the substances. The substances include deposits on a sidewall of the tubular and liquid contained in the tubular. Examples of the deposits include asphaltenes, paraffins, scale, sand, and the like. Gamma rays are strategically directed from a tool disposed within the tubular and to adjacent a sidewall of the tubular. Some of the gamma rays scatter from the substances adjacent the tubular and are detected with detectors set a designated axial distance from the gamma ray source.

Abstract: Fractures at a wellbore wall and in a region surrounding a wellbore wall can be detected by monitoring gamma rays scattered from the fractures. Gamma rays are strategically directed from a tool disposed within the wellbore and to the wall and/or the region. Some of the gamma rays scatter from the fractures and are detected with detectors set a designated axial distance from the gamma ray source. In addition to identifying the presence of the fractures, the location and size of the fractures is also estimated. Based on the location and disposition of the fractures, perforations are formed in the formation to provide communication between the fractures and the wellbore.

Abstract: Fractures at a wellbore wall and in a region surrounding a wellbore wall can be detected by monitoring gamma rays scattered from the fractures. Gamma rays are strategically directed from a tool disposed within the wellbore and to the wall and/or the region. Some of the gamma rays scatter from the fractures and are detected with detectors set a designated axial distance from the gamma ray source. In addition to identifying the presence of the fractures, the location and size of the fractures is also estimated. Based on the location and disposition of the fractures, perforations are formed in the formation to provide communication between the fractures and the wellbore.

Abstract: Substances on or adjacent a tubular disposed in a subterranean wellbore can be detected and/or their presence identified by monitoring gamma rays scattered from the substances. The substances include deposits on a sidewall of the tubular and liquid contained in the tubular. Examples of the deposits include asphaltenes, paraffins, scale, sand, and the like. Gamma rays are strategically directed from a tool disposed within the tubular and to adjacent a sidewall of the tubular. Some of the gamma rays scatter from the substances adjacent the tubular and are detected with detectors set a designated axial distance from the gamma ray source.

Abstract: Methods and devices are provided for accurately determining depths of certain structures in downhole strings. Locator tools comprise a shaft and a plurality of locator springs longitudinally mounted on the shaft. The locator springs are biased to expand and are configured to compress to allow the tool to traverse past restrictions in the downhole string. Each locator spring includes a locating pad that allows it to engage with an internal locating notch in the downhole string. The internal locating notch is sized to mate with the locator tool, i.e., to allow the locator springs to engage the internal locating notch. In this way, the depth of internal locating notches may be determined precisely and accurately by sensing engagement of the tool with the internal locating notch. Advantages of certain embodiments include more accurate depth determination, repeatable engagements of the tool, and reduced false engagements.

Abstract: Monitoring scattered gamma rays is used to identify substances disposed between coaxial tubulars disposed in a subterranean wellbore. Gamma rays are strategically directed from within an inner most tubular and into the annulus, some of the gamma rays scatter from the substance between the tubulars and are detected with detectors set a designated axial distance from the gamma ray source. Gamma rays also scatter from fluid within the tubular, a ratio of the gamma rays detected that scatter from the fluid in the tubular and from the substance can be used to determine the substance.