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Estimating saturation exponent from NMR logging

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Abstract

A new interpretation of the relationship between the saturation exponent (n) and the water saturation (S w ) of a reservoir rock is presented. Based on the capillary theory and Purcell equation, the relationship between resistivity index (I) and the permeability (k), water-phase permeability (k w ) has been obtained. By combining SDR model, such relationship can be transferred into a novel model of probing the saturation exponent under variable saturation conditions. Based on the theoretical derivation, NMR experimental measurements of core examples were implemented to testify the reliability brought by this development. Laboratory measurements of transverse relaxation were carried out on core samples from a formation in the Middle East. NMR experimental measurements were made with 50 samples fully water saturated. Measurements at various air/water saturation (i.e., at residual water saturation) were made on 16 samples among them obtained by different centrifuging speeds. The experimental results show that the calculated saturation exponent values and water saturations follow a power law relationship which is in accordance with researches have been published about that n is not a constant but a variable parameter dependent on water saturation, quantitatively. This study has inferred the quantitative relationship between n and S w through NMR information firstly.

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Acknowledgments

This study was supported by the National Science and Technology Major Project of China (Grant No. 2011ZX05031) (Key Technology of Exploration and Development of Large Projects of Oil & Gas Rich Fields in the Middle East and Central Asia). The authors also would like to thank the reviewers and editors for their attention and valuable comments to improve the manuscript quality.

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Authors and Affiliations

  1. Institute of Geoscience and Technology, Southwest Petroleum University, Chengdu, 610500, China

    Dan Huang, Liqiang Sima, Feng Wu, Liang Wang & Qing Li

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  1. Dan Huang
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  2. Liqiang Sima
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  3. Feng Wu
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  4. Liang Wang
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  5. Qing Li
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Correspondence to Dan Huang.

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Huang, D., Sima, L., Wu, F. et al. Estimating saturation exponent from NMR logging. Arab J Geosci 8, 6771–6778 (2015). https://doi.org/10.1007/s12517-014-1768-1

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  • DOI: https://doi.org/10.1007/s12517-014-1768-1

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