Introduction of Gamma Ray Log

Gamma Ray Log

Introduction of Gamma Ray Log 


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Is the measurement 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 a shaly sand and used for stratigraphic correlations

Gamma ray is a radioactivity log which measured natural radioactivity in the rock

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Properties Of Gamma Ray



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

All gamma-ray encountered in the earth is emitted by uranium

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? The similarity 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

because sp are used only in fresh mud and don't use in salt mud

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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 borehole .the gamma ray detector registers incoming gamma rays as an electronic pulses


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


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Interpretation


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


shale have abundant 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 don't allow impurities to occupy the composition 
thus
sandstone and carbonates have low radioactivity

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


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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 a layer


Describe of radioactive and nonradioactive minerals


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