--> Abstract: Permeability Modeling from Petrophysical Measurements in Tight Gas Sands: Empirical Relations Including Analyses of Saturation Profiles from Individual Porosity Log Responses ; #90055 (2006).
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Previous HitPermeabilityNext Hit Modeling from Petrophysical Measurements in Tight Gas Sands: Empirical Relations Including Analyses of Saturation Profiles from Individual Porosity Log Responses

Holmes, Michael1, Antony Holmes1, Dominic Holmes1 (1) Digital Formation, Inc, Denver, CO

 

Standard petrophysical approaches to estimate Previous HitpermeabilityNext Hit involve comparisons of porosity with irreducible water saturation of the form:

 

Previous HitPermeabilityNext Hit = Constant * Porosity Exponent1 Irreducible Water SaturationExponent2

 

Usually, single values of exponent 1 and exponent 2 are applied to any one reservoir. For tight gas sands, correlations with core-measured Previous HitpermeabilityNext Hit improve if porosity and saturation-dependent values of exponents 1 and 2 are applied, calibrated to the specific reservoir.

 

A second approach to estimating Previous HitpermeabilityNext Hit involves consideration of invasion profiles. We have recently developed fluid substitution techniques whereby gas saturation from individual porosity logs (particularly density and neutron) can be calculated and compared with standard resistivity-based calculations of gas saturation. The comparison shows that in tight gas sands, differences between the calculated gas saturations are a function of Previous HitpermeabilityNext Hit. The conclusion is reached that for these very low matrix Previous HitpermeabilityNext Hit rocks, there is an increasing degree of mud filtrate invasion as Previous HitpermeabilityNext Hit increases. At very low levels of Previous HitpermeabilityNext Hit — less than 50 microdarcies — there is essentially no invasion.

 

Examples from the Rocky Mountains and East Texas are presented, comparing core Previous HitpermeabilityNext Hit with petrophysical estimates of Previous HitpermeabilityTop.

 

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana