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Monday, May 23

  1. page Photoelectric Logging edited By Nhan Nguyen Photoelectric logging is named so because it uses the photo-electric absorption f…
    By Nhan Nguyen
    Photoelectric logging is named so because it uses the photo-electric absorption factor of formations to provide the required data to determine the lithology. It works similarly to the density log and requires a source that steadily emits gamma rays. However the detectors of the photoelectric log are able to determine gamma rays that have higher energies ("hard" gamma rays) and lower energies ("soft" gamma rays).
    "Hard" gamma rays are used in measuring formation density while "soft" gamma rays undergo photo-electric absorption. The photo-electric absorption factor (Pe or PEF) is used to provide a parameter which is dependent upon the atomic number of the formation, which drastically helps to find the formations lithology.
    ...
    {Capture.PNG} The formula for specific photo-electric absorption index.
    {capture_2.PNG} From "Chapter 14 - The Litho-Density Log" - Dr. Paul Glover, Petrophysics MSc Course Notes.

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    2:14 am
  2. page Temperature Logging edited By Nhan Nguyen The temperature log is used to measure the temperature of the borehole. Temperat…
    By Nhan Nguyen
    The temperature log is used to measure the temperature of the borehole. Temperature sensors are attached to any tools that is used in the well to measure the maximum temperature and the minimum temperature of the well.
    The maximum temperature of the borehole is assumed to be at the bottom of the well. The bottom hole temperature (BHT). The BHT and the temperature at the top of the borehole is used to find the geothermal gradient, also known as the geotherm. Borehole temperature is a vital parameter for resistivity logs but is also used to detect any fluid movement in the well, the analysis of fluid pressure, geochemical modeling of formations and the maturity of hydrocarbons.
    (view changes)
    2:14 am
  3. page Caliper Logging edited By Nhan Nguyen The caliper log is one of many logging tools used for measuring the diameter of…

    By Nhan Nguyen
    The caliper log is one of many logging tools used for measuring the diameter of a borehole. It also is able to measure the shape of the borehole. It is a rod with 2 or more spring driven arms that can extend and retract. The arms move in and out along the borehole walls as the caliper is pulled out of the borehole. The in and out movement of the caliper arms are then converted into an electrical signal used to produce a borehole geometry log.
    ===== {caliper_1.jpg}
    {caliper_1.jpg}
    A Caliper
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    arms. (http://www.bakerhughes.com/products-and-services/evaluation/cased-hole-wireline-systems/well-integrity/imaging-caliper-log-icl)
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    =====

    The caliper log is one of many logging tools used for measuring the diameter of a borehole. It also is able to measure the shape of the borehole. It is a rod with 2 or more spring driven arms that can extend and retract. The arms move in a
    nd out along the borehole walls as the caliper is pulled out of the borehole. The in and out movement of the caliper arms are then converted into an electrical signal used to produce a borehole geometry log.
    (view changes)
    2:13 am
  4. page Photoelectric Logging edited alkj Photoelectric logging is named so because it uses the photo-electric absorption factor of fo…
    alkjPhotoelectric logging is named so because it uses the photo-electric absorption factor of formations to provide the required data to determine the lithology. It works similarly to the density log and requires a source that steadily emits gamma rays. However the detectors of the photoelectric log are able to determine gamma rays that have higher energies ("hard" gamma rays) and lower energies ("soft" gamma rays).
    "Hard" gamma rays are used in measuring formation density while "soft" gamma rays undergo photo-electric absorption. The photo-electric absorption factor (Pe or PEF) is used to provide a parameter which is dependent upon the atomic number of the formation, which drastically helps to find the formations lithology.
    Gamma rays are emitted from the source which travel through the rock and scatter and lose energy. As the gamma rays undergo random collisions more energy is loss. "Soft" gamma rays have low energies around the 0.2MeV. Any gamma ray with an energy below the 0.2MeV threshold is completely absorbed into the rock and can encounter an electron under correct conditions. This is photo-electric absorption. Different elements are capable of absorbing different amounts of "soft" gamma rays. The PEF shows the density of the material by how many electrons there are to take part in photo-absorption. Hence the electron density of the rock can be found and so the lithology is determined.
    {Capture.PNG} The formula for specific photo-electric absorption index.
    {capture_2.PNG} From "Chapter 14 - The Litho-Density Log" - Dr. Paul Glover, Petrophysics MSc Course Notes.

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    2:12 am
  5. file capture_2.PNG uploaded
    2:11 am
  6. file Capture.PNG uploaded
    2:09 am
  7. file pescale.gif uploaded
    2:09 am
  8. page References edited ... Products and Services/Resistivity Measurements. (n.d.). Retrieved 05 21, 2011, from Schlumberg…
    ...
    Products and Services/Resistivity Measurements. (n.d.). Retrieved 05 21, 2011, from Schlumberger Limited: http://www.slb.com/services/evaluation/wireline_open_hole/petrophysics/resistivity.aspx
    Nhan Nguyen:
    ...
    Logs" Chapter 99, Chapter 8, Chapter 14
    AnaLog - Caliper Logging Overview (n.d.) Retrieved 19 05 2011 from <http://www.logwell.com/tech/cal/caliper_log.html>
    "Reading the Rocks From Wireline Logs" , Kansas Geological Survey and Oil and Gas Information (n.d) Retrieved 20 05 2011 from <http://www.kgs.ku.edu/PRS/ReadRocks/PEScale.html>
    Richard Yeomans:
    Santana, C and Bai, M (2010) ‘Deriving Rock Mechanical Properties Using Resistivity Log Data’, Halliburton, ARMA 10-173
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    1:14 am
  9. page Temperature Logging edited ... The maximum temperature of the borehole is assumed to be at the bottom of the well. The bottom…
    ...
    The maximum temperature of the borehole is assumed to be at the bottom of the well. The bottom hole temperature (BHT). The BHT and the temperature at the top of the borehole is used to find the geothermal gradient, also known as the geotherm. Borehole temperature is a vital parameter for resistivity logs but is also used to detect any fluid movement in the well, the analysis of fluid pressure, geochemical modeling of formations and the maturity of hydrocarbons.
    Each tool is attached with a temperature sensor. The measurements are always made at the bottom of the well and sometimes at intervals up the well. The general case to measure the temperature was to attach multiple temperature monitors to the outside of a tool string, which would only allow the temperature at the bottom of the borehole to be measure. However, special new temperature logging tools have been developed that allow for continuous reading of temperature up the well.
    {Temperature_Logging.gif} An Example of a Temperature Log <http://hillpetrophysics.com/wp-content/uploads/2010/06/Buildup.gif>
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    1:08 am

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