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Connection equation and shaly-sand correction for electrical resistivity

Scientific Investigations Report 2011-5005

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Abstract

Estimating the amount of conductive and nonconductive constituents in the pore space of sediments by using electrical resistivity logs generally loses accuracy where clays are present in the reservoir. Many different methods and clay models have been proposed to account for the conductivity of clay (termed the shaly-sand correction). In this study, the connectivity equation (CE), which is a new approach to model non-Archie rocks, is used to correct for the clay effect and is compared with results using the Waxman and Smits method. The CE presented here requires no parameters other than an adjustable constant, which can be derived from the resistivity of water-saturated sediments. The new approach was applied to estimate water saturation of laboratory data and to estimate gas hydrate saturations at the Mount Elbert well on the Alaska North Slope. Although not as accurate as the Waxman and Smits method to estimate water saturations for the laboratory measurements, gas hydrate saturations estimated at the Mount Elbert well using the proposed CE are comparable to estimates from the Waxman and Smits method. Considering its simplicity, it has high potential to be used to account for the clay effect on electrical resistivity measurement in other systems.

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Connection equation and shaly-sand correction for electrical resistivity
Series title:
Scientific Investigations Report
Series number:
2011-5005
Edition:
-
Year Published:
2011
Language:
ENGLISH
Publisher:
U.S. Geological Survey
Contributing office(s):
Central Energy Resources Science Center
Description:
iii, 9 p.
Online Only (Y/N):
Y
Additional Online Files(Y/N):
N