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Reservoir Condition Pore-scale Imaging of Multiple Fluid Phases Using X-ray Microtomography
Published on: February 25, 2015
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Characterizing pore-scale structure-flow correlations in sedimentary rocks using magnetic resonance imaging.
K Karlsons1, D W de Kort1,2, A J Sederman1
1Magnetic Resonance Research Centre, Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, United Kingdom.
Physical Review. E
|March 19, 2021
Summary
Magnetic resonance flow imaging reveals highly heterogeneous fluid flow in Ketton limestone. Pore size and topology correlate with flow velocity, impacting transport characteristics and mixing within the rock structure.
Area of Science:
- Geophysics
- Petrophysics
- Fluid Dynamics
Background:
- Understanding fluid flow in porous media is crucial for various applications, including oil recovery and groundwater management.
- Limestone rock formations exhibit complex internal structures that significantly influence fluid transport.
- Previous studies often lacked the resolution to correlate pore-scale structure with localized flow behavior.
Purpose of the Study:
- To quantitatively characterize structure-flow correlations in Ketton limestone using advanced magnetic resonance flow imaging.
- To investigate the relationship between pore geometry (size, topology) and fluid velocity at the microscale.
- To analyze flow dispersion and mixing within the rock's pore space.
Main Methods:
- Quantitative, 3D spatially resolved magnetic resonance flow imaging (flow MRI) with undersampled k- and q-space acquisition.
- Compressed sensing (CS) for data reconstruction.
- Coregistration of MRI data with X-ray microcomputed tomography (μCT) for structural analysis.
- Analysis of 3D velocity maps and spatially resolved propagators.
Main Results:
- Flow MRI at 35 μm resolution revealed highly heterogeneous flow: ~10% of pores carried >50% of the flow.
- Direct correlations found between pore size, topology (coordination number), and local flow velocities.
- Flow patterns in Ketton limestone showed similarities to flow through sphere packings, suggesting grain consolidation.
- Analysis of local propagators indicated enhanced mixing within the pore space over longer observation times.
- The length scale of a representative elementary volume was not reached for a 4-mm plug.
Conclusions:
- Spatially resolved flow MRI effectively visualizes and quantifies pore-scale flow heterogeneity in rocks.
- Pore structure significantly dictates fluid transport characteristics and dispersion in limestone.
- The study highlights the limitations of representative elementary volume assumptions at this scale.
- These findings advance the understanding of fluid dynamics in complex geological formations.
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