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Shale Volume Calculation

Irfan SaputraHRS Jakarta

CE8R2/ March 2008

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Introduction

Shale is usually more radioactive than sand or carbonate, gamma ray log can

be used to calculate volume of shale in porous reservoirs. The volume of shale

expressed as a decimal fraction or percentage is called Vshale.

Calculation of the gamma ray index is the first step needed to determine the

volume of shale from gamma ray log.

All of the prs files are available in the LogMath section of the Hampson-Russell

Knowledgebase for copying and pasting into the LogMath window.

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Various Equation for Vshale Calculation

The gamma ray log has several nonlinear empirical responses as well a linear

responses. The non linear responses are based on geographic area or formation age.

All non linear relationships are more optimistic that is they produce a shale volume

value lower than that from the linear equation.

minmax

minlog

GRGR

GRGRIVGRsh

==

Linear response (Vshale = IGR) :

Vshale_linear.prs

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Various Equation for V shale Calculation

The nonlinear responses are :

Larionov (1969) for older rock :

Clavier (1971) :

Steiber (1970) :

Larionov (1969) for Tertiary rocks : )12(083.0 7.3

= GR

I

shV

GR

GR

sh

I

IV

=

23

[ ]21

2)7.0(38.3(7.1 +=GRsh

IV

)12(33.0 2

= GR

I

shV

Vshale_Larionov_Tertiary_Rock.prs

Vshale_Steiber.prs

Vshale_Clavier.prs

Vshale_Larionov_Older_Rock.prs

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Comparison of All Methods

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References

Asquith, G., and D. Krygowski, 2004, Basic Well Log Analysis: AAPG Methods

in Exploration 16, p.31-35