Quantifying the Effect of Kerogen on Resistivity Measurements in Organic-Rich Mudrocks
- Nikhil Kethireddy (Texas A&M University) | Huangye Chen (Texas A&M University) | Zoya Heidari (Texas A&M University)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- April 2014
- Document Type
- Journal Paper
- 136 - 146
- 2014. Society of Petrophysicists & Well Log Analysts
- 4 in the last 30 days
- 489 since 2007
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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 fluid saturation in organic-rich mudrocks, using well logs and core measurements from the Haynesville Shale. We then numerically simulated the electric field, electric currents, and effective resistivity of synthetic pore-scale rock images. Finally, we used numerical simulation to quantify the effects of the (a) volumetric concentration of kerogen, (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 first step towards improving conventional resistivity-porositysaturation models for the assessment of fluid saturations in organic-rich mudrocks.
|File Size||11 MB||Number of Pages||11|