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Measuring pore connectivity by pulsed field gradient diffusion editing with hydrocarbon gases
Mark Flaum1, George Jiro Hirasaki, Charles Flaum
1Department of Chemical Engineering, Rice University MS 362, Rice University PO Box 1892, Houston, TX 77251-1892, USA. mflaum@rice.edu
Magnetic Resonance Imaging
|April 19, 2005
Summary
This study measured time-dependent diffusion in rock samples using nuclear magnetic resonance. Different behaviors were observed for water, methane, and ethane, revealing insights into pore network connectivity.
Area of Science:
- Geophysics
- Materials Science
- Physical Chemistry
Background:
- Understanding fluid transport in porous media is crucial for resource exploration and management.
- Nuclear Magnetic Resonance (NMR) offers non-invasive techniques to probe subsurface properties.
Purpose of the Study:
- To investigate time-dependent diffusion (D(t)) in a rock sample saturated with different fluids.
- To explore the influence of fluid type (water, methane, ethane) and relaxation time on diffusion behavior.
- To identify pore network characteristics using diffusion measurements.
Main Methods:
- Time-dependent diffusion measurements using pulse field gradient diffusion editing NMR sequences.
- Analysis of diffusion coefficients (D(t)) as a function of relaxation time.
- Utilizing methane and ethane for their higher diffusivity and longer relaxation times compared to water.
Main Results:
- Distinct time-dependent diffusion behaviors were observed for water, methane, and ethane.
- Diffusion characteristics varied significantly with different relaxation times.
- Evidence of connected pore networks was detected at moderate relaxation times.
Conclusions:
- Fluid type and relaxation time critically influence diffusion measurements in rocks.
- NMR diffusion editing is effective in characterizing pore structure and connectivity.
- Findings provide insights into fluid flow mechanisms within porous geological formations.