Biomedical subjects

YQ Song

Publications and source records attributed to YQ Song.

4 recordsLinked to original sources

PubMed2000

Detection of the high eigenmodes of spin diffusion in porous media

The dynamics of spin diffusion in a fluid is governed by the Torrey-Bloch equations, and the solution is often expressed mathematically in an eigenmode expansion. We report an experimental demonstration of the excitation and detection of a wide range of eigenmodes in porous media by exploring the inhomogeneous internal magnetic field in the pore space. The nodal character of the eigenfunctions of the high eigenmodes was clearly observed. The methodology of excitation and detection of the high eigenmodes may be used to better characterize pore geometry.

Journal Article↗

PubMed2000

Determining multiple length scales in rocks

Carbonate reservoirs in the Middle East are believed to contain about half of the world's oil. The processes of sedimentation and diagenesis produce in carbonate rocks microporous grains and a wide range of pore sizes, resulting in a complex spatial distribution of pores and pore connectivity. This heterogeneity makes it difficult to determine by conventional techniques the characteristic pore-length scales, which control fluid transport properties. Here we present a bulk-measurement technique that is nondestructive and capable of extracting multiple length scales from carbonate rocks. The technique uses nuclear magnetic resonance to exploit the spatially varying magnetic field inside the pore space itself--a 'fingerprint' of the pore structure. We found three primary length scales (1-100 microm) in the Middle-East carbonate rocks and determined that the pores are well connected and spatially mixed. Such information is critical for reliably estimating the amount of capillary-bound water in the rock, which is important for efficient oil production. This method might also be used to complement other techniques for the study of shaly sand reservoirs and compartmentalization in cells and tissues.

Journal Article↗

PubMed2000

Determining pore sizes using an internal magnetic field

A concept is proposed to measure the pore size length scale by the internal magnetic field (B(i)) in porous materials. The spatial distribution of the magnetic field inhomogeneity, a result of the magnetic susceptibility contrast between the porous material and the fluid, reflects the underlying pore geometry. Diffusion in B(i) causes the initial decay of magnetization. At long times, the effect of B(i) saturates when the diffusion length reaches a characteristic pore size. This method is independent of surface spin relaxation in determining pore sizes. Nuclear magnetic resonance experiments on packed glass beads and sedimentary rock samples will be presented. Copyright 2000 Academic Press.

Journal Article↗

PubMed1994

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