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Coarse-scale resistivity for saturation estimation in heterogeneous reservoirs based on Archie's formula

Per Atle Olsen
Coarse-scale resistivity for saturation estimation in heterogeneous reservoirs based on Archie's formula
Geophysics (March 2011) 76 (2): E35-E43

Abstract

Relations between porosity, saturation, and resistivity are essential when estimating in-place hydrocarbon volumes. The most common relation is the Archie formula. During the last decade, several new coarse-scale electromagnetic techniques for resistivity measurements have been developed. Applications of coarse-scale resistivity must consider the underlying geologic variability of porosity and saturation to be used in such relations. I have investigated the effect of small-scale (logging-scale) variability in porosity and water saturation on coarse-scale resistivity for Archie relations. An analytical expression for coarse-scale resistivity is derived based on the assumption of lognormal distributed porosity and saturation. Similarly, coarse-scale water saturation is derived assuming lognormal distributed porosity and resistivity. The results suggest that the coarse-scale equivalent Archie resistivity is normally less than the geometric average and larger than the harmonic average of the heterogeneous resistivity distribution. An important aspect of the analytical derived relations is the quantification of the effect of the variability (variance and covariance) on the coarse-scale results. Another coarse-scale average resistivity based on macroscopic anisotropy could be a practical approximation of the coarse-scale equivalent Archie resistivity in many cases.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 76
Serial Issue: 2
Title: Coarse-scale resistivity for saturation estimation in heterogeneous reservoirs based on Archie's formula
Author(s): Olsen, Per Atle
Affiliation: Statoil, Trondheim, Norway
Pages: E35-E43
Published: 201103
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 19
Accession Number: 2011-061177
Categories: Applied geophysicsEconomic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201134
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