• Saturday, June 6, 2015

    Introduction of Gamma Ray Log

    Gamma Ray Log


    Is the measurment of the natural radioactivity of formation in general shales tend to have high radioactivity while sandstone-limestone-salt-anhydrite have low radioactivity

    Its tools used to determine shae content in ashaly sand and used for stratigraphic correlations

    Gamma ray is aradioactivity log which measured natural radio activity in the rock

    ******************************************************

    Properties Of Gamma Ray



    Gamma rays burst of high energy electro magnetic waves that are emitted by radioactive elements

    All gamma ray encountered in the earth is emmitted by uranium

    ******************************************************

    ? The similarty between Gamma Ray and  SP



    The gamma ray is similar to sp and gamma ray is replace the sp in salt muds and in air filled holes and when Rmf=Rw

    becous sp are used only in fresh mud and dont use in salt mud

    ******************************************************

    Theory 

    Gamma ray are high energy electromagnetic waves produced by the  decay of radioactivity isotopes such as 
    k40-th-u

    The rays pass from the formation and enter the bore hole .the gamma ray detector registers incomming gamma rays as an electronic pulses

    The pulse are sent to the uphole computer where they are counted and timed

    ******************************************************

    Interpretation

    The interpretation of gamma ray curve is based on the assumption that

    shale have abundent potassium 40 in their composition the open lattice structure and waves bonds in clays encourage incorporation of impurities the most common of these impurities are uranium-thorium

    thus

    shales have high radioactivity 

    sandstone,quartz,carbonates have strong bonds and generally dont allow impurities occupy the composition 
    thus
    sand stone and carbonates have low radioactivity

    limestone undergo rearrangement of crystal structure and addition magnesium to become dolomite

    ******************************************************
    Advantage of Gamma Ray

    Good shale indicator

    Good correlations

    Gamma ray can be run in open and cased hole

    Used to determine the top and the bottom of layer

    Discribe of radioactive and nonradioactive minerals