Pore geometry information via pulsed field gradient NMR.

Studies of echo attenuation at long diffusion times in pulsed field gradient NMR experiments on a variety of rock core samples are interpreted in the light of recent theoretical analysis of the effect of pore geometry and surface relaxation. This study is motivated by the need to test the applicability of that theory to real rock systems.

3D autocorrelation for the determination of large pore sizes.

A data analysis methodology is used to process 3D NMR image data acquired for porous systems. The method extracts the mean size of those repeating elements in the image data which are largely compared with the image voxel dimensions. In this work we extend the two-dimensional (2D) image analysis method described by others to three spatial dimensions (3D). 3D image data were acquired at a magnetic field strength of 7 T using NMR microscopy hardware. The 3D autocorrelation function obtained from the data reveals a characteristic pore size in each dimension.

Strategies for overcoming linewidth limitations in quantitative petrophysical NMR measurements.

The simple pulse-acquire experiment has been used to evaluate the level of accuracy and precision achievable in NMR fluid saturation measurements for a range of rock core samples saturated with either brine or hydrocarbons. For a set of more than 70 cores measured at 0.66 T the mean error in the NMR measurement is only 0.35% porosity when the sample linewidths are less than 50 ppm. However, for a significant portion of cores, those with very broad NMR linewidths (> 50 ppm), difficulties associated with nonuniform excitation are encountered. The magnetic susceptibility difference between pore fluid and rock matrix translates into relatively broad NMR linewidths, and this feature of petrophysical samples is the major difficulty in performing quantitative NMR experiments. Numerical simulations are used to complement the experimental results in order to develop strategies for obtaining accurate NMR results with these difficult samples.

Quantitative longitudinal fluid saturation profiles with a slice-selected CPMG sequence.

A technique for obtaining quantitative longitudinal saturation/porosity profiles of rock cores which are longer than the NMR coil has been developed. The slice-selected experiment uses a prefocused pulse in conjunction with a magnetic field gradient for the localization and a CPMG sequence to sample the data. A variety of rock core samples has been studied ranging from limestones to shaly sandstones. Comparison of the relaxation decay curves obtained from these experiments and the bulk experiments show that reliable localized relaxation data are obtained.

Variation of composition with particle size in coal liquid aerosols generated for inhalation toxicology studies.

The chemical composition and microbial mutagenicity of aerosols generated by nebulizing two coal oils (solvent refined coal [SRC]-I process solvent [PS] and SRC-II heavy distillate) were found to vary with particle size. Significant quantities of the most volatile components of PS were also present as vapors. Evaporation and condensation processes in oil deposited on surfaces as well as in the aerosol are believed to be important in determining the observed composition changes. Complete physical and chemical characterization of the aerosol should be included in inhalation studies of complex materials since the animals may be exposed to material of quite different composition than that placed in the generator initially.

Tobacco smoke inhalation studies: a dosimetric comparison of different cigarette types.

As part of a long-term inhalation bioassay study of cigarette smoke in rats, a detailed dosimetric comparison of three groups of rats exposed to smoke from different cigarette types was performed. Groups of 20 female F-344 rats were exposed, in Maddox-ORNL smoking machines, to 14C-dotriacontane-labeled smoke from three types of research cigarettes: high tar-low nicotine, low tar-high nicotine, and high tar-high nicotine. Analyses of lung tissues revealed similar deposition amounts and patterns of particulate matter for all three cigarette types even though the chamber smoke concentrations varied substantially. These results suggested that for rats exposed to different types of cigarette smoke, the amount of particulate material deposited may not be a function of concentration only. The authors conclude that when comparing cigarette smoke inhalation studies of different cigarette types, exposure parameters and smoke composition may both influence the amount of smoke inhaled and deposited in the lung and other organs.