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J Magn Reson ; 310: 106649, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31778887


A method for characterising water and oil in a rock core plug using correlations between diffusion decay in internal magnetic gradient and transverse relaxation time (DG02-T2) is presented. The method is evaluated at different saturation levels and is compared with the measurement of correlations between diffusion and transverse relaxation time (D-T2). It is shown how signals from water and oil can be separated based on their difference in diffusion decay in internal gradients. The obtained results show that the impact from heterogeneity in pore geometry and mineralogy on the individual liquids is revealed in more detail in DG02-T2 correlations compared to the more established D-T2 correlations. Measurements of DG02-T2 correlations should be included in the toolbox of NMR experiments performed in the laboratory analysis of rock core plugs, and could then potentially lead to more detailed estimations of saturation levels and surface wettability properties.

J Magn Reson ; 259: 1-9, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26254732


In the method Decay due to Diffusion in the Internal Field (DDIF), the diffusion behaviour of water molecules in the internal magnetic field makes it possible to determine a distribution of pore sizes in a sample. The DDIF experiment can also be extended to a DDIF-Carr-Purcell-Meiboom-Gill (DDIF-CPMG) experiment to measure correlations between the pore size and the transverse relaxation time, T2. In this study we have for the first time applied the DDIF experiment and the DDIF-CPMG experiment to porous materials saturated with both water and oil. Because of the large difference in diffusion rates between water and oil molecules, the DDIF experiment will act as a filter for the signal from oil, and we are left with the DDIF-signal from water only. This has been verified in model systems consisting of glass beads immersed in separate layers of water and oil, and in a sandstone sample saturated with water and oil. The results show that the DDIF and DDIF-CPMG experiments enable the determination of the confining geometry of the water phase, and how this geometry is correlated to T2. Data obtained in the sandstone sample saturated with water and oil also show that with the exception of the smallest pores there is no clear correlation between pore size and the relaxation time of water.

J Colloid Interface Sci ; 296(1): 64-70, 2006 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-16165143


The adsorption of poly(styrene sulfonate), PSS, of different molecular weights (70,000, 500,000, and 1,000,000 mol/kg), from aqueous solutions on alpha-alumina has been investigated. PSS of the lower molecular weight adsorbs less than the others whose adsorption isotherms overlap. The adsorption is found to increase with increasing ionic strength of the solutions indicating that both electrostatic and non-electrostatic contributions are involved in the adsorption process. Upon addition of the anionic surfactant, sodium dodecyl sulfate, SDS, PSS is found to adsorb less the more SDS added. SDS is found to be preferentially adsorbed as shown both from the simultaneous adsorption of the components and also from the sequential adsorption process where SDS in all cases displaces preadsorbed PSS from the solid surface. The displacement of preadsorbed polyelectrolyte by surfactant is a very slow process and the displacement is less pronounced as the molecular mass of the polyelectrolyte increases indicating the fewer number of contact points to the surface. This is further underlined by the effect on the displacement of PSS by SDS upon increasing the ionic strength of the solutions.