Quantifying the Effect of Kerogen on Resistivity Measurement
Interpretation of resistivity logs in organic-rich mudrocks has been challenging for petrophysicists. Conventional resistivity-porosity-saturation models (e.g., Archie, dual-water, and Waxman-Smits) assume that the pore water is the only conductive part of the formation. However, this assumption is not reliable in the presence of the thermally mature organic matter, clay, and pyrite found in many source rocks. Previous experimental studies indicate that as the aromaticity of kerogen increases with increasing thermal maturity, the conductive behavior of kerogen is also affected. In this paper, we investigated the effect of conductive kerogen on the resistivity of mature source rocks.
We investigated the reliability of conventional resistivity-porosity-saturation models for estimating uid saturation in organic-rich mudrocks, using well logs and core measurements from the Haynesville Shale. We then numerically simulated the electric eld, electric currents, and effective resistivity of synthetic pore-scale rock
images. Finally, we used numerical simulation to quantify theeffectsofthe(a)volumetricconcentrationofkerogen, (b) kerogen conductivity, and (c) spatial connectivity of the kerogen-water network on the resistivity of organic-rich mudrocks.
Well-log interpretation of the Haynesville Shale showed that conventional resistivity-porosity-saturation models underestimate hydrocarbon saturation in zones with high concentrations of kerogen. In this paper, we show that errors in the estimation of of hydrocarbon saturation could be due to the effect of kerogen on resistivity measurements. Our pore-scale numerical simulations show that there is a 10 to 23% improvement in hydrocarbon-saturation estimates, when the impact of conductive kerogen is taken into account. Results of this work can be used as a rst step towards improving conventional resistivity-porosity- saturation models for the assessment of uid saturations in organic-rich mudrocks.
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Author(s):
Nikhil Kethireddy2, Huangye Chen3 and Zoya Heidari3
Company(s):
Previously with Texas A&M University, Harold Vance Department of Petroleum Engineering, College Stat
Year:
2014