The nuclear magnetic resonance method in researches of structure of porous space in the conditions of a filtration

On the basis of experimental results obtained in Example sandstones at different fluid flow rates by PFG NMR it is shown in principle the possibility of registering and determining the relative proportion of dead or stagnant zones. The possibility to study molecular exchange between molecules diffusing into the stagnant zones, and the molecules involved in the flow

Studying residual fluid in anisotropic natural core GR-201 and NAV-221 by NMR relaxometry

Indices FFI (free fluid index-the index of free fluids, which corresponds to the fraction of the liquid in the macropores and therefore quite easily retrievable) and BVI (bound volume index-index-related (residual) fluids-the proportion is difficult to extract the liquid in either the micropores in which the liquid is held by strong capillary forces, or in the closed pores) were calculated from the analysis of the relaxation data obtained in the case of complete saturation of the core samples with water/hexane. Comparative analysis of the relaxation characteristics of the cores before and after thermochemical treatment is given. Residual fluid and its influence on the spectrum shape of relaxation times are defined according to the relaxation data

Studying anisotropic natural core GR-201 and NAV-221 by NMR

The paper presents results of the research core GR-201 and the NAV-221, characterized by spatial anisotropy. Translational mobility of the molecules diffusing in dependence not only on the diffusion time, but the orientation of the sample relative to the direction of the external magnetic field gradient is studied

Internal magnetic field gradients as information source about porous media characteristics

The geometry of particles is analyzed by the example of a model porous system (filling of glass spheres and glass cylinders) studied by nuclear magnetic resonance. The experimental approach is based on the registration of the 〈Gint〉(ζ) dependences, where 〈G int〉 is the effective (average) internal magnetic field gradient and ζ = 〈r2〉1/2/〈R〉 is the ratio of the root-mean-square displacement of molecules to the average particle size 〈R〉. It is shown that the dependence 〈Gint〉 (ζ) can be approximated by the power law 〈Gint〉(ζ ) ∝ ζα, where the power index α does not depend on the particle size but is sensitive to its geometry. © Springer-Verlag 2005

The Low-Field Pulsed Mode Dynamic Nuclear Polarization in the Pentavalent Chromium Complex and Crude Oils

© 2014 Springer-Verlag Wien Measurements of the enhancement of the proton resonance signal right after applying the radiofrequency pulse with the variable duration in the magnetic field of about 100 Gauss on the homebuilt prototype of the dynamic nuclear polarization (DNP) spectrometer at near room temperature are presented. A dependence of the DNP enhancement of the solvent protons of the solution of the pentavalent chromium complex in ethylene glycol on the pumping pulse duration and incident pumping power is given. No DNP effect on the native protons of the crude oils and natural bitumen from the Russian oilfields is observed. A miserable DNP enhancement is registered on the protons of toluene by dissolving the crude oil and bitumen samples. The perspectives of using the results and technical solutions for geological exploration, studies of the asphaltene structures and their dynamics are discussed

The low-field pulsed mode dynamic nuclear polarization in the pentavalent chromium complex and crude oils

© Springer-Verlag Wien 2014. Measurements of the enhancement of the proton resonance signal right after applying the radiofrequency pulse with the variable duration in the magnetic field of about 100 Gauss on the homebuilt prototype of the dynamic nuclear polarization (DNP) spectrometer at near room temperature are presented. A dependence of the DNP enhancement of the solvent protons of the solution of the pentavalent chromium complex in ethylene glycol on the pumping pulse duration and incident pumping power is given. No DNP effect on the native protons of the crude oils and natural bitumen from the Russian oilfields is observed. A miserable DNP enhancement is registered on the protons of toluene by dissolving the crude oil and bitumen samples. The perspectives of using the results and technical solutions for geological exploration, studies of the asphaltene structures and their dynamics are discussed

Features of coupling between rheological properties of oil and natural bitumen and the self-diffusion data obtained by NMR method

This paper describes the features of translational characteristics of oil molecules by using nuclear magnetic resonance method with pulsed magnetic field gradient (gradient NMR). It is shown that the rheological properties of heavy oil samples (viscosity) do not completely correlate with the measurement of self-diffusion coefficient. It is caused by distribution of oil samples according to their molecular composition and molecular weight as well as their complex supramolecular organization. It is noted that the best agreement with the viscosity characteristics is achieved via the introduction of a new average coefficient, which is a weighted sum of the inverse of the partial self-diffusion coefficients

Excited States of Ladder-type Poly-p-phenylene Oligomers

Ground state properties and excited states of ladder-type paraphenylene oligomers are calculated applying semiempirical methods for up to eleven phenylene rings. The results are in qualitative agreement with experimental data. A new scheme to interpret the excited states is developed which reveals the excitonic nature of the excited states. The electron-hole pair of the S1-state has a mean distance of approximately 4 Angstroem.Comment: 24 pages, 21 figure

Determination of hydroxyl groups in biorefinery resources via quantitative 31P NMR spectroscopy

The analysis of chemical structural characteristics of biorefinery product streams (such as lignin and tannin) has advanced substantially over the past decade, with traditional wet-chemical techniques being replaced or supplemented by NMR methodologies. Quantitative 31P NMR spectroscopy is a promising technique for the analysis of hydroxyl groups because of its unique characterization capability and broad potential applicability across the biorefinery research community. This protocol describes procedures for (i) the preparation/solubilization of lignin and tannin, (ii) the phosphitylation of their hydroxyl groups, (iii) NMR acquisition details, and (iv) the ensuing data analyses and means to precisely calculate the content of the different types of hydroxyl groups. Compared with traditional wet-chemical techniques, the technique of quantitative 31P NMR spectroscopy offers unique advantages in measuring hydroxyl groups in a single spectrum with high signal resolution. The method provides complete quantitative information about the hydroxyl groups with small amounts of sample (~30 mg) within a relatively short experimental time (~30-120 min)