Predicting Fluid Flow Regime, Permeability, and Diffusivity in Mudrocks from Multiscale Pore Characterisation

Amirsaman Rezaeyan*, Vitaliy Pipich, Jingsheng Ma, Leon Leu, Timo Seemann, Gernot Rother, Lester C. Barnsley, Andreas Busch

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

In geoenergy applications, mudrocks prevent fluids to leak from temporary (H2, CH4) or permanent (CO2, radioactive waste) storage/disposal sites and serve as a source and reservoir for unconventional oil and gas. Understanding transport properties integrated with dominant fluid flow mechanisms in mudrocks is essential to better predict the performance of mudrocks within these applications. In this study, small-angle neutron scattering (SANS) experiments were conducted on 71 samples from 13 different sets of mudrocks across the globe to capture the pore structure of nearly the full pore size spectrum (2 nm–5 μm). We develop fractal models to predict transport properties (permeability and diffusivity) based on the SANS-derived pore size distributions. The results indicate that transport phenomena in mudrocks are intrinsically pore size-dependent. Depending on hydrostatic pore pressures, transition flow develops in micropores, slip flow in meso- and macropores, and continuum flow in larger macropores. Fluid flow regimes progress towards larger pore sizes during reservoir depletion or smaller pore sizes during fluid storage, so when pressure is decreased or increased, respectively. Capturing the heterogeneity of mudrocks by considering fractal dimension and tortuosity fractal dimension for defined pore size ranges, fractal models integrate apparent permeability with slip flow, Darcy permeability with continuum flow, and gas diffusivity with diffusion flow in the matrix. This new model of pore size-dependent transport and integrated transport properties using fractal models yields a systematic approach that can also inform multiscale multi-physics models to better understand fluid flow and transport phenomena in mudrocks on the reservoir and basin scale.

Original languageEnglish
Pages (from-to)201-229
Number of pages29
JournalTransport in Porous Media
Volume141
Issue number1
Early online date16 Nov 2021
DOIs
Publication statusPublished - Jan 2022

Keywords

  • Diffusivity
  • Fluid flow regimes
  • Fractal modelling
  • Permeability
  • Pore size distribution
  • Small-angle neutron scattering

ASJC Scopus subject areas

  • Catalysis
  • Chemical Engineering(all)

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