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GR Log Interpretation

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Density-Neutron

Log

2.0 2.2 2.4 2.6 2.8 3.0

42 30 18 6 -6 -18

Neutron (pu)

Lithology Porosity Fluid

Salt

Anhydrite

Limestone

Limestone

Dolomite

Shale

Sandstone

Sandsto

ne

Sandsto

ne

5%

15%

Water

Water

15% Water

20% Gas

20% Oil

20% Water

Density

(g/cm3)

Limestone compatible scales

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Spontaneous Potential (SP)Spontaneous Potential (SP)

SP

Shale

Sand Thick clean wet sand

(-) (+)

- - - - - - -

- - - - - - -

Thick shaly wet sand

Thick clean Gas sand

Thick shaly Gas sand

Rmf >> Rw inall sands

Hydrocarbon effect

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How Can We Remember These Easily?How Can We Remember These Easily?

About Lithology Interpretation

Claystone - has large amount of water, and radioactive materials, is denser when it has

less water, is not harder than limestone and is very conductive.

Sandstone- is less dense than limestone, has less water than clay, contain more water

than limestone except when it is saturated with dry gas, its conductivity is depending on

fluid type it contains, has small to none radioactive fragments.

Limestone - is harder than both clay and sand, contains least water of the three, very

resistive, it has low radioactivity materials, fast velocity, high density.

Coal - Normaly low radioactive, rarely radioactive, lowest density and very resistive

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How Can We Remember These Easily?How Can We Remember These Easily?About Fluid Interpretation

High Radioactivity - High GR

Very Conductive - Low Resistivity

High Water - High Neutron and Low Resistivity

High Gas - Low Neutron and High Resistivity

High Oil - Higher Neutron than Gas, denserthan gas Less Neutron than water,

less dense than water, more

resistive than water, less-

resistive than gas when other

properties are the same

Dry Gas - Very resistive, largest density

neutron crossover

High GOR - Larger density-neutron crossover

than oil with low GOR

Fresh Water - Reservoir filled with high resistive water