Transport in Porous Media

, Volume 124, Issue 1, pp 73–90 | Cite as

A Novel Method for Gas–Water Relative Permeability Measurement of Coal Using NMR Relaxation

  • Xiaoxiao Sun
  • Yanbin YaoEmail author
  • Nino Ripepi
  • Dameng Liu


Using the conventional volumetric method in unsteady-state relative permeability measurements for unconventional gas reservoirs, such as coal and gas shale, is a significant challenge because the movable water volume in coal or shale is too small to be detected. Moreover, the dead volume in the measurement system adds extra inaccuracy to the displaced water determination. In this study, a low-field nuclear magnetic resonance (NMR) spectrometer was introduced into a custom-built relative permeability measurement apparatus, and a new method was developed to accurately quantify the displaced water, avoiding the drawback of the dead volume. The changes of water in the coal matrix and cleats were monitored during the unsteady-state displacement experiments. Relative permeability curves for two Chinese anthracite and bituminous coals were obtained, matching the existing research results from the Chinese coalbed methane area. Moreover, the influences of confining pressure on the shape of the relative permeability curve were evaluated. Although uncertainties and limits exist, the NMR-based method is a practical and applicable method to evaluate the gas/water relative permeability of ultra-low permeability rocks.


Coalbed methane Relative permeability Unconventional gas reservoir NMR 

List of symbols


Amplitude index


Air-dry-based ash yield


Air-dry-based fixed carbon content


Fractional flow of water in outlet stream


Volume percentages of inertinite in coal maceral composition


Relative injectivity


Relative permeability of gas


Relative permeability of water


Volume percentages of liptinite in coal maceral composition


Air-dry-based moisture content


Volume percentage of minerals on a dry basis


Cumulative water produced


Peaks in T2 distribution spectra


Inlet gas pressure


Outlet gas pressure


Total flow rate or gas injection rate


Mean maximum vitrinite reflectance in oil


Surface-to-volume ratio


Outlet gas saturation


Gas saturation at crossing points


Initial gas saturation


Irreducible water saturation


Total amplitude of T2 at the initial displacement time


Proton NMR transverse relaxation time


Total amplitude of T2 at different displacement times


Volume percentages of vitrinite in coal maceral composition


Cumulative gas injected

Greek symbols


Pressure difference


Injection gas volume under inlet gas pressure at a given interval value


Surface relaxivity


Gas viscosities


Water viscosities



Bulk relaxation


Surface relaxation



We acknowledge financial support from the National Natural Science Foundation of China (41472137), the National Major Research Program for Science and Technology of China (2016ZX05043-001), the Fundamental Research Funds for the Central Universities (2652016124) and China Scholarship Council (201606400013).

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.

Data Availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.


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© Springer Science+Business Media B.V., part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Energy ResourceChina University of GeosciencesBeijingPeople’s Republic of China
  2. 2.Coal Reservoir Laboratory of National Engineering Research Center of CBM Development and UtilizationChina University of GeosciencesBeijingPeople’s Republic of China
  3. 3.Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development EngineeringChina University of GeosciencesBeijingPeople’s Republic of China
  4. 4.Department of Mining and Minerals EngineeringVirginia Polytechnic Institute and State UniversityBlacksburgUSA

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