NMR imaging of materials for transport properties
AssigneeShell Oil Company
InventorsHarold J. Vinegar, William P. Rothwell
Life of this patent
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Abstract
NMR imaging methods are provided for determining spatial diffusion coefficients, formation resistivity factors, mean pore size, and permeability of a porous material. The imaging methods employ a constant magnetic field and two images are obtained for the material, one with a non-imaging gradient and one without a non-imaging gradient. These images are combined to produce diffusion coefficients.
Claims9
A method for determining spatial transport characteristics of a subsurface earth specimen, comprising:
- NMR imaging said specimen with a constant magnetic field and with a zero applied field gradient and, then MMR imaging said specimen with a constant magnetic field and with a non-zero applied field gradient.
A method for determining the diffusion coefficient of a porous material, comprising:
- NMR imaging said material with a constant magnetic field to determine a first spatial image and then NMR imaging said material with a constant magnetic field and a gradient magnetic field to determine second spatial image, and
- functionally combining the intensities of said first and second image for each corresponding pixel of said spatial images to provide a spatial image of said diffusion coefficient.
A method for determining the formation resistivity factor of a porous material, comprising:
- NMR imaging said material with increasing interpulse times with a constant magnetic field to determine a first spatial image and then NMR imaging said material with said increasing interpulse times with a constant magnetic field and a gradient magnetic field to determine a second spatial image,
- determining from said first and second spatial image a diffusion coefficient independent of interpulse time variation for each pixel of said spatial image,
- determining the bulk diffusion coefficient of the nuclei being imaged, and
- functionally combining said bulk diffusion and diffusion coefficients to provide a spatial image of said formation resistivity factor.
A method for determining mean pore size of a porous material comprising:
- NMR imaging said material with increasing interpulse times to determine the smallest interpulse time for which a diffusion coefficient becomes independent of interpulse time,
- determining the bulk diffusion coefficient of the nuclei being imaged, and
- functionally combining said interpulse time and bulk diffusion coefficient to provide a spatial image of said mean pore size.
A method for determining permeability of a porous material, comprising:
- NMR imaging said material with increasing interpulse times to determine the smallest interpulse time for which a diffusion coefficient becomes independent of interpulse time, and
- functionally combining said smallest interpulse time and diffusion coefficient to provide a spatial image of said permeability.
A method for determining permeability of a porous material, comprising:
- NMR imaging said material with increasing interpulse times to determine the smallest interpulse time for which a diffusion coefficient becomes independent of time,
- determining a bulk diffusion coefficient, and
- functionally combining said smallest interpulse time, and said bulk diffusion and diffusion coefficients to provide a spatial image of said permeability.
Dependencies are inferred from the claim text.