Este trabajo describe un procedimiento no destructivo para la determinación del contenido de agua líquida en poros de rocas sedimentarias mediante mediciones de la Capacidad Dieléctrica (CD). Los estudios se concentraron en determinar el contenido de agua en rocas de formaciones petrolíferas constituidas por esquistos bituminosos (shales) cuya principal característica es que poseen baja porosidad y muy baja o nula permeabilidad. En particular, los testigos se obtuvieron de muestra de coronas, con sus fluidos preservados pertenecientes a la cuenca de Vaca Muerta, Neuquén, Argentina. Los resultados obtenidos muestran que este método permite determinar el contenido de agua lo cual permite evaluar la cantidad de petróleo a partir de las mediciones del contenido total de protones (petróleo más agua o índice de protones) medible mediante Resonancia Magnética Nuclear (RMN).

This work describes a non-destructive procedure for the determination of liquid water content in pores of sedimentary and shale rocks by means of measurements of the dielelectric capacity (CD).These studies concentrates on determining the water content in rocks, mainly from oil shale reservoirs, whose principal characteristic are its very low permeability, low porosity and small pore sizes. The samples provided were preserved rotated plugs from the Vaca Muerta basin (Neuquen, Argentina). The results show that this method allows precise determination of the water content which turns out relevant in order to evaluate the amount of oil from Nuclear Magnetic Resonance (NMR) measurements of the total proton content (assuming the oil hydrogen index equals to one).

The present work involves a comprehensive study to provide a theoretical model of the internal magnetic field gradients, present in paramagnetic shale pores, to explain the main relaxation features observed by nuclear magnetic resonance transversal relaxation measurements. In the systematic analysis process of relaxation data it is necessary to know up to what extent the magnetic field gradients are generated by the logging tool and/or arise internally in the rock due to their paramagnetic impurities content. The physical model to explain the relaxation features is based on the calculation of field gradients in a planar pore with and without relaxatives walls. The results reproduce the features of the relaxation parameters in pores due to paramagnetic and tortuous walls. The mechanism that drives the relaxation process is governed by anomalous diffusion within micro-pores. These relaxation processes arise from the interactions between the protons, belonging to the liquid molecules and the pore walls, whose structure is characterized by both large tortuosity and abundance of paramagnetic impurities, giving rise to local strong time dependent magnetic field gradients. The theoretical results are compared with those obtained experimentally to validate the relaxation model. The experimental data were gathered from a sample belonging to the “Vaca Muerta” formation of the Neuquén basin, Argentina.

The present work involves a comprehensive experimental study of proton (1 H) nuclear magnetic resonance (NMR) transversal relaxation in shale. The sample studied belongs to the “Vaca Muerta” formation of the Neuquén basin, Argentina. The results show that the relaxation process is governed by anomalous diffusion processes in micro-pores. These processes result from the combination of interactions between the liquid molecules and the pore walls, whose structure is characterized by both large tortuosity and abundance of paramagnetic impurities, giving rise to local strong time-dependent magnetic field gradients. In addition, a simultaneous experimental method of data fitting is presented which allows processing all the relaxation profiles within a single time domain. Thus, yielding results univocally related to the complete set of relaxation data.

The present work involves a comprehensive experimental study of porosity and pore size distribution of sedimentary rocks, from oil fields formations, by means of two electromagnetic techniques, namely proton ( 1 H) nuclear magnetic resonance (NMR) and dielectric complex constant (DCC) as function of the frequency, both providing complementary results. The NMR yields an accurate determination of the relative pore size distribution and both movable and irreducible fluids. The DCC measurement provides the direct current electrical resistivity of the samples with different degrees of hydration. Thus, combining the results of both techniques allows the determination of the tortuosity index, by means of Archie’s relation, and from it the average pore channel length. These measurements are performed on fully hydrated (saturated), centrifuged, dried, and cleaned rocks and also on samples with the irreducible fluids. Finally, the results are complemented with capillary pressure measurements to obtain the total volume associated with the pore channels related to the rock permeability. Additionally, the work presents a particular method to use a network analyzer to measure the DCC.

A NMR probe for low frequency and short recovery time is presented in this work. The probe contains the tuning circuit, diode expanders and quarter wavelength networks to protect the receiver from both the amplifier noise and the coil ringing following the transmitter power pulse. It also possesses a coil damper which is activated by of non active components. The probe performance shows a recovery time of about of , a sensitive Q factor reduction and an increase of the signal to noise ratio of about 68% during the reception at a work frequency of . Introduction An important reason for the use of low frequency NMR pulsed spectrometers applied to petro-physics studies is that nuclear relaxation caused by fixed paramagnetic impurities, rising from the interaction between the nuclear spin and unpaired electron spins, is better detected al low fields. 1, 2 This feature is in conflict with several characteristic design of the spectrometer blocks, this is because the signal to noise ratio (ξ), the natural ringing time () and the quality factor (Q) of the probe coil have a frequency dependence that comes into play. This work describes both the design criteria design and the advantages of a relatively simple probe with a non active damping circuit for the above mentioned NMR studies. The probe, in a conventional NMR spectrometer, is connected to the power amplifier and to the receiver, in a T shape configuration, in such a way to allow the rf power to go into the probe and the nuclear signal input only to the preamplifier. These three blocks of the spectrometer, the transmitter, the probe and the receiver, are usually interconnected in the well known Lowe ⁄ arrangement. 4 The probe must be tuned in such a way that during the rf pulse its impedance should be adjusted to the output impedance of the transmitter to ensure the maximum power transfer (a). Simultaneously, the receiver should be isolated from the probe to protect it from large rf voltages (b). During the reception, the probe should be isolated from the transmitter output to avoid noise and the weak nuclear signal should be driven to the receiver input. Also the probe should have a short ringing (c) time after the rf pulses, and the signal to noise ratio of the NMR signal (d) should be as high as possible. Additionally, the interconnections between the three blocks depend also of the frequency and its variations generate instruments artifacts that adversely affect both the signal to noise ration and the Ann. Magn. Reson. Vol. 10, Issue 3, 28-36, 2011 AUREMN 29 data collection (e). Features (c) and (d) are interrelated since  depends of Q being

En este trabajo se estudian las características dinámicas del agua de hidratación de una mezcla normal de gangliósidos utilizando la técnica de resonancia magnética nuclear. Mediciones de tiempos de relajación espín-espín permiten identificar dos rnicroambientes bien diferenciados para el agua, cuyos tiempos de correlación rotacional están en el rango 10-9 -10-8 s y 10-11 -10-10 s a temperatura ambiente. Para una relación agua/gangliósido 200:1 (mol:mol) se determina que aproximadamente 30 moléculas de agua están fuertemente ligadas a cada gangliósido y que las propiedades dinámicas del resto están alteradas respecto de las del agua libre

Se presenta un estudio de los espectros de Resonancia Magnética Nuclear de los protones y deuterios en dos ferrofluídos diferentes. Uno de ellos contiene partículas magnéticas surfactadas dispersadas en una mezcla de agua y agua deuterada. Las particulas magnéticas de la otra muestra son granos de γ - Fe2O3 con carga positiva. Se propone un modelo para la distribución de campos magnéticos en el agua intersticial basado en la simulación numérica del campo producido por una distribución de dipolos magnéticos orientados en un campo externo. Con este modelo se describe el ensanchamiento y la asimetría de los espectros de RMN observados.

The present work involves a comprehensive experimental determination of porosity and pore size distribution in rocks from oil fields formations by deuterium (2H) Nuclear Magnetic Resonance (NMR) and Positronium Annihilation Lifetime Spectroscopy (PALS). Both techniques yield complementary results; PALS measures the average pore size providing bulk information from which the most abundant pore size can be obtained, and NMR allows for the determination of the relative pore size distribution accurately. Both techniques give complementary information to obtain an absolute pore size distribution.

The standard use of the centrifuge is to determine capillary pressure in plugs. What is proposed in this work is to extend its application making it possible to determine the pore-throat size distribution in plugs in addition to the capillary pressure indicated above. To this end we start with a plug properly cleaned and saturated with the corresponding brine. The plug is then placed in the centrifuge and the collected data consists of the total evacuated brine volume VT(v) as a function of the centrifuge rotation speed v. A simple model, consisting of capillary tubes running from one end of the plug to the other, is proposed to describe the complex system network of pores and the corresponding interconnecting pore-throats. The corresponding theory, based on treating the capillary pressure as that due to the water-air interphase, is worked out in such a way as to link the capillary size distribution to VT(v) vs. v. The mathematical procedures turn out to be straightforward and the solution is unique. This original analysis of the centrifuge data was successfully applied to a large number of plugs. As an example the corresponding data and analyses are fully given and described. In a companion paper these results are compared with those obtained by MICP (Mercury Injection Core Porosimetry), and the agreement found may be considered as excellent. There is a practical limitation of the method proposed in this work. The capillary pressures that can be reached with the centrifuge are not as high as those that can be reached by MICP. This limitation manifests itself in the fact that pore-throat sizes below 1 μm are poorly detected or not detected at all. However, for pore-throat sizes above that value the agreement is excellent. The main result obtained in this work is that it is shown that similar information to that produced in a MICP run with two main advantages (1) the centrifuge is a non-destructive experiment, and (2) is a non-contaminating experiment.

A combined study of 2 H nuclear magnetic resonance lineshape and spin-lattice and spin-spin relaxation times as functions of temperature and the amount of hydration water in a cross-linked copolymer of sucrose and 1,4-butadienol diglycidyl ether in the hydrogel phase is reported. The results show strong evidence that the onset of the relaxation mechanisms is driven by anomalous water molecule diffusion depending on both temperature and the hydration degree of the hydrogel. In addition, these results are correlated with the transitions observed by differential thermal analysis.

In a previous nuclear magnetic resonance (NMR) study we observed that the NMR spectra of water in both surfacted and ionic ferrofluids are asymmetric and several orders of magnitude wider than the one of pure water. It has been proposed that this effect is produced by extremely strong magnetic field gradients in the intergrain volume and/or by surface interactions between the carrier liquid molecules and the grains surface. In the case of aqueous ionic ferrofluids the latter possibility should be interpreted as electric interactions between water (polar) molecules and the charges in the grain surface. In this work we study a series of ionic and surfacted ferrofluids prepared at different magnetic grain concentrations and sizes, and with different surface charge densities. Our experiments clearly show that the sign and the density of the electric charge on the magnetic grains have no influence on NMR spectra. On the other hand, spectral widths increase with the magnetic grain concentration.

In a previous NMR study [Gonzalez, C.E.; et al. J. Chem. Phys. 1998, 109, 4670] we observed that the H-1 and H-2 spectra of both surfacted and ionic ferrofluids are broad and asymmetric. In ionic ferrofluids, this effect could be due to (i) electric interactions between the electrically charged magnetic grains and the electric dipole moments of water molecules and/or (ii) the interaction between water molecules and the distribution of magnetic field gradients in the intergrain volume. In this work we study a series of ionic ferrofluids prepared at different magnetic grains concentrations and with different surface charge densities. Our experiments clearly show that the sign and the density of the electric charge of the magnetic grains have no influence on the NMR spectra. On the other hand, spectral widths increase with the magnetic grains concentration, all the samples being far from the motional narrowing regime.

This work reports a nuclear magnetic resonance (NMR) study of both hydrogen and deuterium on two different kinds of ferrofluids. One of them is a colloidal suspension of surfacted magnetic grains dispersed in a mixture of light and heavy water. The second one is an ionic ferrofluid composed by positively charged magnetic grains of Co–Fe2O4 dispersed in the same solution of water. A model of the local magnetic field distribution in the interstitial (bulk) water is worked out in order to account for the broadening of the NMR spectra observed in both samples.

A combined study of flow-induced optical birefringence, x-ray diffraction, optical observations, electrical measurements and 23Na NMR is reported with the aim to characterize the phase diagram of the ternary lyotropic mixture of sodium bis (2 ethylhexyl) sulfosuccinate, dodecanol, and water. One of the most interesting features of this phase diagram is the existence of a bicontinuous structure associated to an inverted sponge phase in the amphiphilic-rich region of it. This phase is surrounded by a micellar isotropic inverted phase. Besides these phases, a lamellar and a cylindrical (triclinic) phase were observed in the phase diagram.