Nuclear Magnetic Resonance T2 Research Articles

Study on Nuclear Magnetic Resonance Logging T2 Spectrum Shape Correction of Sandstone Reservoirs in Oil-Based Mud Wells.

The oil-based mud filtrate will invade the formation under the overbalanced pressure during drilling operations. As a result, alterations will occur to the nuclear magnetic resonance (NMR) response characteristics of the original formation, causing the relaxation time of the NMR T2 spectrum of the free fluid part to move towards a slower relaxation time. Consequently, the subsequent interpretation and petrophysical evaluation will be heavily impacted. Therefore, the actual measured T2 spectrum needs to be corrected for invasion. For this reason, considering the low-porosity and low-permeability of sandstone gas formations in the East China Sea as the research object, a new method to correct the incorrect shape of the NMR logging T2 spectrum was proposed in three main steps. First, the differences in the morphology of the NMR logging T2 spectrum between oil-based mud wells and water-based mud wells in adjacent wells were analyzed based on the NMR relaxation mechanism. Second, rocks were divided into four categories according to the pore structure, and the NMR logging T2 spectrum was extracted using the multidimensional matrix method to establish the T2 spectrum of water-based mud wells and oil-based mud wells. Finally, the correctness of the method was verified by two T2 spectrum correction examples of oil-based mud wells in the study area. The results show that the corrected NMR T2 spectrum eliminates the influence of oil-based mud filtrate and improves the accuracy of NMR logging for calculating permeability.

Effect of Grain Size on Microscopic Pore Structure and Fractal Characteristics of Carbonate-Based Sand and Silicate-Based Sand

In this study, a series of nuclear magnetic resonance (NMR) tests was conducted on calcareous sand, quartz sand, and glass bead with a wide range of grain sizes, to understand the effect of grain size on the micro-pore structure and fractal characteristics of the carbonate-based sand and silicate-based sand. The pore size distribution (PSD) of the tested materials were obtained from the NMR T2 spectra, and fractal theory was introduced to describe the fractal properties of PSD. Results demonstrate that grain size has a significant effect on the PSD of carbonate-based sand and silicate-based sand. As grain size increases, the PSD of sands evolves from a binary structure with two peaks to a ternary structure with three peaks. The increase in the grain size can cause a remarkable increase in the maximum pore size. It is also found that the more irregular the particle shape, the better the continuity between the large and medium pores. In addition, grain size has a considerable effect on the fractal dimension of the micro-pore structure. The increase of grain size can lead to a significant increase in the heterogeneity and fractal dimension in PSD for calcareous sand, quartz sand and glass bead.

Research on the Influence of Gas on Coal Pores based on NMR Technology

In order to study the change characteristics of the pore structure of coal under different CH4 pressure conditions, nuclear magnetic resonance (NMR) technology was used to test the degree of influence on porosity and pore size distribution of coal after the adsorption of CH4 under different pressures. The test results show that under the action of gas pressure, the NMR signal amplitude of the NMR T2 spectrum changes significantly. From the distribution area of the T2 spectrum of the coal sample, it can be known that the peak peak area of small holes>the peak peak area of medium and large holes>the peak peak area of cracks indicates that the coal sample The micropores in the coal body are the most developed, and the connectivity is not strong, and it is difficult to circulate; in the range of gas pressure P=0.5~2.0MPa, as the gas pressure increases, new pores will be generated in the coal body, and the micropores are interconnected to form micropores or medium Pores and mesopores are interconnected to form cracks, thereby increasing the porosity and permeability of the coal sample.

Impact of Xylose on Dynamics of Water Diffusion in Mesoporous Zeolites Measured by NMR.

Zeolites are known to be effective catalysts in biomass converting processes. Understanding the mesoporous structure and dynamics within it during such reactions is important in effectively utilizing them. Nuclear magnetic resonance (NMR) T2 relaxation and diffusion measurements, using a high-power radio frequency probe, are shown to characterize the dynamics of water in mesoporous commercially made 5A zeolite beads before and after the introduction of xylose. Xylose is the starting point in the dehydration into furfural. The results indicate xylose slightly enhances rotational mobility while it decreases translational motion through altering the permeability, K, throughout the porous structure. The measurements show xylose inhibits pure water from relocating into larger pores within the zeolite beads where it eventually is expelled from the bead itself.

Accurate characterization of coal pore and fissure structure based on CT 3D reconstruction and NMR

In order to accurately achieve the full-scale characterization of coal pore and fissure structure, a comprehensive characterization method based on Computed Tomography (CT) 3D reconstruction, Nuclear Magnetic Resonance (NMR) T2 spectrum and Nuclear Magnetic Imaging (NMI) are proposed. CT scanning and NMR experiments are carried out on the samples of gas coal and anthracite to verify this method. And the characteristics of pore size distribution (PSD), porosity and permeability are studied. It is found that the main seepage channels can be obtained by CT 3D reconstruction, and that the observation defect of CT scanning can be compensated by NMI because micro seepage pores and adsorption pores can be visualized. Furthermore, CT 3D reconstruction results indicate that the larger the pore size, the smaller the number of pores, and the larger the porosity component while the NMR T2 spectrum of pore size distribution show that the porosity component of micro adsorption pores is largest. With the advantage of CT macro-scale observation and NMR micro-scale observation combined, porosities are calculated accurately. Besides, seepage characteristics observed in the NMR experiments under different water injection pressures are analyzed, and the results are consistent with the analysis results of the CT 3D reconstruction of coal connectivity.

CO2 – brine – sandstone wettability evaluation at reservoir conditions via Nuclear Magnetic Resonance measurements

CO2-rock wettability is a key parameter which governs CO2 trapping capacities and containment security in the context of CO2 geo-sequestration schemes. However, significant uncertainties still exist in terms of predicting CO2 rock wettability at true reservoir conditions. This study thus reports on wettability measurements via independent Nuclear Magnetic Resonance (NMR) experiments on sandstone (CO2–brine systems) to quantify Wettability Indices (WI) using the United States Bureau of Mines (USBM) scale. The results show that CO2 (either molecularly dissolved or as a separate supercritical phase) significantly reduced the hydrophilicity of the sandstone from strongly water-wet (WI ≈ 1) to weakly water-wet (WI = 0.26), and associated with that the water-wetness of the rock for the two-phase systems. This was caused by additional protonation of surface silanol groups on the quartz, induced by carbonic acid. Capillary pressure and relative permeability curves and residual CO2 saturation were also measured; these results were compared with literature data, and general consistency was found. NMR T2 distribution measurements also demonstrated preferential water displacement in large pores (r > 1 µm) following scCO2 flooding, while no change was observed for smaller pores (r < 1 µm). These insights add confidence to the assessments of CO2-rock wettability and therefore reduce project risk. This work thus aids in the implementation of large-scale CO2 sequestration.

Applying NMR T2 Spectral Parameters in Pore Structure Evaluation—An Example from an Eocene Low-Permeability Sandstone Reservoir

The Eocene low-permeability sandstone reservoirs in the Dongying Depression, Bohai Bay Basin, China host a significant amount of oil reserves. The development of the reservoirs has been hampered by our inability to understand the complex and heterogeneous pore structures of the reservoirs. In this study, the pore systems, pore sizes, pore connectivity, and movable fluid distribution of the Eocene Shahejie Formation (Es4) sandstone reservoirs were investigated using an integrated analysis of optical and scanning electron microscopy (SEM), mercury injection capillary pressure (MICP), and nuclear magnetic resonance (NMR). The full-range pore structures of the Es4 sandstone reservoirs were evaluated by using NMR experiments. Various NMR T2 spectral parameters suitable for describing the pore structures and movable fluid distribution were extracted through morphological and statistical analysis of NMR T2 spectra. In combination with corresponding MICP data and petrophysical properties, we have demonstrated the reliability and robustness of the T2 spectral parameters for pore structure characterization. Four types of pore structures (I, II, III, and IV) were distinguished from the NMR T2 spectral parameters in association with other petrophysical properties and macroscopic behaviors. We have demonstrated the effectiveness of using the NMR T2 spectral parameters to characterize and classify micropore structures, which may be applied to effectively evaluate and predict low-permeability reservoir quality.

Monitoring oil displacement and CO2 trapping in low-permeability media using NMR: A comparison of miscible and immiscible flooding

Dynamic monitoring of the internal fluid distribution during CO2 immiscible/miscible flooding provides a crucial window for illuminating key processes controlling displacement and transport. We used online low-field nuclear magnetic resonance (NMR) imaging to monitor CO2 flooding under different reservoir pressures in low-permeability siltstone core plugs pre-saturated with stock tank oil from the Chang72 Formation in China. Immiscible and miscible styles of fluid displacement were triggered by flooding at pressures of 8 and 16 MPa, respectively. To visualize the oil distribution, NMR T2 and T1–T2 spectra and one-dimensional frequency (1D-FQ), and magnetic resonance imaging (MRI) were conducted to obtain the overall and spatially distributed saturations. The results show that recovery by miscible flooding (69.4%) was twice more than that by immiscible flooding (32.6%). The effect of the extraction of lighter components on oil viscosity and density after CO2 injection was negligible compared to the changes in miscibility. CO2 concentrations at the leading edge of the miscible zone (0.526) were higher than in the immediately adjacent transition zone (0.1); the dimensionless widths were 0.76 and 0.44, respectively. The CO2 retention rate following miscible flooding was 10.59% higher than that due to immiscible flooding, primarily due to remnant dissolved CO2 in the oil. In contrast, immiscible flooding limited the solubility of CO2 and led to solubility and residual trapping. These observations have a significant impact on defining oil and CO2 budgets, modes of transport, and storage for enhanced oil recovery and CO2 sequestration.

NMR Fluid Substitution–A New Method of Reconstructing T2 Distributions Under Primary Drainage and Imbibition Conditions

Most nuclear magnetic resonance (NMR)-based petrophysics models, such as pore structure characterization and permeability prediction, were developed using T2 distributions measured at fully water-saturated conditions (i.e., Sw = 1). The downhole implementation of those models across the hydrocarbon zones is disputable due to partial saturation (Sw &lt; 1) conditions; hence, a correction to such effects on T2 distributions is required. This paper provides a critical review of the fluid substitution methods currently available in the industry and presents an improved method for enhanced formation evaluation. In the new method presented, an effective irreducible water saturation model is used to account for the pore structure and capillary pressure effects, which were barely considered by the currently available NMR fluid substitution methods. For water-wet reservoir rocks, the typical NMR T2 distribution at the partial saturation condition displays a clear separation between the wetting and nonwetting phases. The water phase can be classified as irreducible and movable fluid volumes. Then, using a T2 mapping relationship and a total porosity constraint, the T2 distribution of movable water at Sw &lt; 1 is shifted and amplified to determine the T2 distribution of movable water at Sw = 1. To validate the new method, NMR measurements were conducted on sandstone samples at Sw = 1 as well as Sw &lt; 1. The reconstructed T2 distribution at Sw = 1 was compared with the measured T2 distribution at Sw = 1. Results showed that the reconstructed T2 distribution matched very well with the T2 distribution measured at Sw = 1, confirming the robustness of the new technique. Parameters used in the reconstruction methodology are observed to be a good indicator of pore connectivity. During desaturation, the water T2 in large pores shifts to a shorter T2 because of the enhanced surface relaxation as the water volume decreases while the surface area remains constant. Therefore, the amplitude at the short T2 increases. The increased amplitude was remapped to large pores in reconstructing T2 spectra of full saturation.

Spontaneous imbibition characteristics of carbon nanofluids in carbonate reservoirs

Altering the wettability of the rock–oil–brine system plays a substantial role in the oil recovery process from carbonate reservoirs. Hence, there arises a need for understanding the wetting and wettability alteration of this system. In this study, we ran a suite of spontaneous imbibition tests and investigated the efficiency of Carbon nanodots (CND) and an in-house cationic Gemini surfactant (GS8) on the wettability alteration of and recovery from oil-wet carbonate rock samples. The study considered the effects of additives concentrations, sample aging, initial water saturation, and rock permeability. Both CND and GS8 proved efficient at concentrations below 200 ppm. At 200 ppm, separately CND in seawater and GS8 in seawater demonstrated each about 22%–25% incremental oil recovery over neat seawater. Low field nuclear magnetic resonance (NMR) measurements supported this observation. NMR T2 distribution and NMR T2D fluid typing measurements helped evaluate the recovery in terms of the pore size distribution and the oil and brine water saturation at different imbibition stages. CND exhibited a strong positive effect on the wettability of all tested samples, and accordingly, on the imbibition characteristics and oil recovery. It altered the wettability from strongly oil-wet to water-wet with equal efficiency in all pore systems making it a strong candidate for enhanced oil recovery (EOR). GS8, on the other hand, was most efficient in the macropores. Unlike CND, the efficiency of GS8 decreased in the mesopores and more so in the micropores. Rock–oil–brine surface contact angle and oil–brine interfacial tension measurements supported the imbibition test results and helped interpret the recovery mechanism. Overall, CND proved effective for EOR in the harsh carbonate reservoir environment and demonstrated itself as a viable and economical substitute to the more costly and complex oilfield chemicals for recovery operations.

Understanding the microstructural evolution of hypersaline cemented paste backfill with low-field NMR relaxation

Cemented paste backfill (CPB) comprising mineral tailings, binders and mixing water is an important potential support material in the mining industry. As the mechanical properties of CPB are significantly influenced by its microstructural characteristics the development of measurement tools to better understand its pore structure evolution is important for its increased utilisation. This study reports the application of low-field nuclear magnetic resonance (NMR) relaxation time measurements to characterise the microstructural evolution of CPB materials over 56 days of hydration, contrasting common tap water and hypersaline water (~22 wt% salt) as mixing water. Distinct NMR relaxation time populations were evidenced within each CPB sample, revealing the presence of both capillary (T1,2 ≈ 10 ms) and gel pore water (T1,2 ≈ 300–500 μs), with time-dependent relaxation measurements facilitating characterisation of capillary pore structure evolution over the hydration period assessed. Hypersaline samples demonstrated a time-lag in this measured capillary pore evolution, relative to those hydrated with tap water, while pore structure evolution rates were observed to increase with increased CPB binder content. Further, both T1 and T2 NMR relaxation times were found to correlate with the uniaxial compressive strength of the CPB materials investigated, facilitating the formulation of a predictive correlation function between NMR relaxation characteristics and mechanical properties.

Objective-Driven Solid-Surface-Roughness Characterization for Enhanced Nuclear-Magnetic-Resonance Petrophysics

Summary Typically, smooth solid surfaces of reservoir rocks are assumed in formation evaluation, such as nuclear-magnetic-resonance (NMR) petrophysics and reservoir-wettability characterization through contact-angle measurements. Measuring the degree of surface roughness (R), or smoothness, and evaluating its effects on formation evaluation are topics of much research. In this paper, we primarily focus on details in characterizing solid-surface roughness and its applications in NMR pore-size analysis. R can be measured by contact techniques and noncontact techniques, such as stylus profilometer, atomic-force microscopy, and different kinds of optical measurements. Each technique has different sensitivities, measurement artifacts, resolutions, and field of view (FOV). Intuitively, although a finer resolution measurement provides the closest account of all surface details, the correspondingly small FOV might compromise the representativeness of the measurement, which is particularly challenging for charactering heterogeneous samples such as carbonates. To balance the FOV and measurement representativeness, and to minimize artifacts, laser scanner confocal microscopy (LSCM) is selected in this study. Results for the more than 27 rock samples tested indicate that rocks of similar rock types have similar R-values. Grainy limestones have relatively higher R-values compared with dolostones, consistent with the dolostone’s crystallization surface features. Muddy limestones have smoother surfaces, resulting in the lowest R-values among the rocks studied. For sandstones, R varies with clay types and content. For rocks containing two distinct minerals, two R-values are observed from the R profiles, which for these rock types justifies the use of two NMR surface relaxivity (ρ2) parameters for determining the pore-size distribution (PSD) from the NMR T2 distribution. The novelty here is the integration of LSCM and NMR to obtain an NMR PSD relevant for permeability, capillary pressure, and other petrophysical parameters. Typically, ρ2 is calibrated using the total surface area from Brunauer-Emmett-Teller (BET; Brunauer et al. 1938) gas adsorption, but this underestimates the NMR pore size because of surface-roughness effects. In our novel approach, we use R measured from LSCM to correct ρ2 for surface-roughness effects, and thereby obtain the NMR pore size more relevant for permeability and other petrophysical parameters. We then compare the roughness-corrected NMR PSD against pore size from microcomputed tomography (micro-CT) scanning (which is roughness independent). The good agreement between roughness-corrected NMR and micro-CT pore sizes in the micropore region validates our new technique, and highlights the importance of surface-roughness characterization in NMR petrophysics.

Experimental investigation of the pore structure characteristics for the high-salt formation in Qianjiang depression, China

Special attention has recently been paid to the high-salt formation in Qianjiang depression as its abundant oil resources with ultra-low permeability and porosity. However, the complex pore structure characteristic of the high-salt formation has not been well understood so far because of its pore size ranging from nanometer to micrometer scale. This paper aims to investigate the complex pore structure characteristic of the target high-salt formation based on an integrated experimental approach involving X-ray diffraction (XRD), scanning electron microscope (SEM), mercury injection capillary pressure (MICP), casting lamella observation and nuclear magnetic resonance (NMR) techniques. XRD analysis results indicate that the target formation mainly includes clastic mineral, carbonate mineral and salt mineral, and the content of them are 32.16%, 36.59%, and 24.65%, respectively. The results of SEM and casting lamella observation indicate that storage space of target formation can be divided into intercrystal pores, solution pores, and fractures. Solution pores have great impact on oil production, which includes dolomite dissolved pore and glauberite dissolved pore. Based on the MICP test results, the samples can be divided into pore type and fracture-pore type. The average pore radius of pore type samples and fracture-pore type samples are 0.0144 μm and 0.40 μm, respectively. Pore size distribution (PSD) results from MICP indicate that single peaks appeared in PSD curves of pore type samples and multi-peaks appeared in PSD curves of fracture-pore type samples. Permeability contribution peaks of pore type samples range from 0.01 to 0.03 μm, and permeability contribution peaks of fracture-pore type samples range from 1 to 10 μm. Comparing the permeability contribution of pore type samples and fracture-pore type samples reveals that mesopores and macropores make the vast majority of permeability contribution of the two kind type samples. A method to get permeability contribution of pore throats from PSD results has been introduced in this paper based on T2 NMR test. Comparing the PSD results from MICP and T2 NMR test results shows that T2 NMR test can identify smaller pore throat.

Distribution characteristics of movable fluid in tight sandstone based on nuclear magnetic resonance

Movable fluid parameter is an important index to evaluate the seepage characteristics of tight sandstone reservoir. Combined with high-pressure displacement and nuclear magnetic resonance movable fluid testing principle, the nuclear magnetic resonance movable fluid characteristics of six typical tight sandstone core samples of Xujiahe Formation in Central Sichuan Basin were studied. Based on mercury injection capillary pressure curve, the nuclear magnetic resonance T2 spectrum distribution was converted into pore throat According to the radius distribution, the minimum pore throat radius of the movable fluid and the contribution of different pore sizes to the movable fluid are determined. The research shows that the movable fluid saturation of the tight sandstone reservoir in the second member of Xujiahe Formation in Central Sichuan is closely related to the pressure difference, with good logarithmic correlation, and the main contribution to the movable fluid saturation is the reservoir space > 0.1 μm. 70% of the total movable fluid saturation is injected at a lower pressure (about 5MPa). In the later stage, high pressure injection can only enter the reservoir pore with small pore size, and the total amount is small and increases slowly. Therefore, the total contribution of high pressure drive to gas saturation in the later stage is small.

Stochastic Modelling of 13C NMR Spin Relaxation Experiments in Oligosaccharides.

A framework for the stochastic description of relaxation processes in flexible macromolecules including dissipative effects has been recently introduced, starting from an atomistic view, describing the joint relaxation of internal coordinates and global degrees of freedom, and depending on parameters recoverable from classic force fields (energetics) and medium modelling at the continuum level (friction tensors). The new approach provides a rational context for the interpretation of magnetic resonance relaxation experiments. In its simplest formulation, the semi-flexible Brownian (SFB) model has been until now shown to reproduce correctly correlation functions and spectral densities related to orientational properties obtained by direct molecular dynamics simulations of peptides. Here, for the first time, we applied directly the SFB approach to the practical evaluation of high-quality 13C nuclear magnetic resonance relaxation parameters, and , and the heteronuclear NOE of several oligosaccharides, which were previously interpreted on the basis of refined ad hoc modelling. The calculated NMR relaxation parameters were in agreement with the experimental data, showing that this general approach can be applied to diverse classes of molecular systems, with the minimal usage of adjustable parameters.

An experimental study on the effect of magnetic field strength and internal gradient on NMR-Derived petrophysical properties of sandstones

Nuclear Magnetic Resonance (NMR) is being widely deployed as a powerful tool for estimating petrophysical properties. Compared to conventional carbonate reservoirs, sandstone reservoirs contain a high amount of paramagnetic ions (such as iron, nickel, or manganese) usually found in clays. The interpretation of NMR-derived petrophysical properties for sandstone formation can be complicated due to the paramagnetic ions which cause inhomogeneity in the magnetic field called internal gradient. Earlier studies focused on investigating the impact of clays and field strength on internal gradient, but implications for estimating NMR-derived petrophysical properties are not well understood yet. This study aims to investigate the impact of the internal gradient and magnetic field strength on the T2 relaxation times and the NMR-derived porosity, T2 logarithmic mean value (T2,LM), and permeability. NMR T2 measurements at several echo times were performed to evaluate the internal gradient for six sandstone samples characterized by variable porosity, permeability, and clay contents/mineralogy. The analysis was executed at two different operating Larmor frequencies (2 and 12 MHz), which are the most common frequencies for rock core analysis. The results show that the internal gradient magnitude increases with the increase of the paramagnetic-rich clays (Chlorite and Illite in the studied samples) while no correlation is observed with Kaolinite content. Furthermore, the internal gradient's magnitude and effect are consistently more pronounced at the 12 MHz measurements than those performed at 2 MHz. Porosity estimates from NMR are found to be independent of the internal gradient and the magnetic field strength as long as sufficiently low echo time (0.2 ms) is used. Unlike porosity, noticeable discrepancies in T2,LM were reported between 2 MHz and 12 MHz measurements, with the later showing consistently lower T2,LM values. The discrepancies in T2,LM values result in significant differences (up to 300%) when calculating NMR-derived permeability using the same formulations for both 2 and 12 MHz data. That is, calibration done using the T2 data from 12 MHz equipment cannot be applied for permeability estimation from lower field NMR data (like logging NMR). The discrepancies between 2 and 12 MHz in terms of T2,LM and derived-permeability increase exponentially as the internal gradient increases but such discrepancies diminish for tight rocks (permeability < 1 mD). This behavior of the tight sandstone samples is attributed to the relaxation regime, which is impacted by pore sizes. If pores are small enough, such as the case occasionally for shale or tight sandstone, relaxations move from a short time regime to the motionally averaged. In such a regime, the internal gradient is averaged by diffusion over the length scale, meaning that relaxation time has no dependence on echo time.

Research on Prediction of Movable Fluid Percentage in Unconventional Reservoir Based on Deep Learning

In order to improve the measurement speed and prediction accuracy of unconventional reservoir parameters, the deep neural network (DNN) is used to predict movable fluid percentage of unconventional reservoirs. The Adam optimizer is used in the DNN model to ensure the stability and accuracy of the model in the gradient descent process, and the prediction effect is compared with the back propagation neural network (BPNN), K-nearest neighbor (KNN), and support vector regression model (SVR). During network training, L2 regularization is used to avoid over-fitting and improve the generalization ability of the model. Taking nuclear magnetic resonance (NMR) T2 spectrum data of laboratory unconventional core as input features, the influence of model hyperparameters on the prediction accuracy of reservoir movable fluids is also experimentally analyzed. Experimental results show that, compared with BPNN, KNN, and SVR, the deep neural network model has a better prediction effect on movable fluid percentage of unconventional reservoirs; when the model depth is five layers, the prediction accuracy of movable fluid percentage reaches the highest value, the predicted value of the DNN model is in high agreement with the laboratory measured value. Therefore, the movable fluid percentage prediction model of unconventional oil reservoirs based on the deep neural network model can provide certain guidance for the intelligent development of the laboratory’s reservoir parameter measurement.

Analysis of Extra Virgin Olive Oils from Two Italian Regions by Means of Proton Nuclear Magnetic Resonance Relaxation and Relaxometry Measurements.

The interest in development of new non-destructive methods for characterization of extra virgin olive oils (EVOOs) has been increasing in the recent years. Among different experimental techniques, nuclear magnetic resonance (NMR) relaxation measurements are very promising in the field of food characterization and authentication. In this study, we focused on relaxation times T1 and T2 measured at different magnetic field strengths (namely, 2, 100, and 400 MHz) and 1H NMR T1 relaxometry dispersions directly on olive oil samples without any chemical/physical treatments. A large set of EVOO samples produced in two regions of Italy, Tuscany and Apulia, were investigated by means of 1H NMR relaxation techniques. The relaxation studies reported here show several common features between the two sets of EVOO samples, thus indicating that relaxation properties, namely, the ranges of values of T1 and T2 at 2 and 100 MHz, are characteristic of EVOOs, independently from the cultivars, climate, and geographic origin. This is a promising result in view of quality control and monitoring.

Fractal behaviors of NMR saturated and centrifugal T2 spectra in oil shale reservoirs: The Paleogene Funing formation in Subei basin, China

Fluorescence thin section and scanning electron microscopy (SEM) analysis were performed to delineate pore spaces and pore network assemblages of oil shales of Member 2 of Paleogene Funing Formation (E1f2) in Subei Basin, China. Nuclear magnetic resonance (NMR) T2 (transverse relaxation time) spectra were used to gain insight into pore size distribution. Fractal analysis was performed on the NMR T2 spectra measured at saturated and centrifugal status, respectively, with the aim to reveal the different fractal behaviors of irreducible pore realms (centrifugal T2 spectrum) and the entire pore systems (saturated T2 spectrum). Relationships between NMR parameters and fractal dimensions were revealed. The results show that the pore spaces consist of 1) large pore realms including interparticle pores, and microfractures, 2) small pore realms including intragranular dissolution pores, intercrystal micropores and organic matter pores. The T2 spectra are mostly bimodal and left-skewed due to abundance in small pore realms. The right peak or tail distribution is associated with large pore realms. Fractal analysis performed on saturated and centrifugal T2 spectra show that fractal dimensions calculated from centrifugal T2 spectrum are higher. In addition, fractal dimensions for centrifugal T2 spectrum show negative correlation relationships with BVI and T2cutoff values. The different fractal behaviors of saturated and centrifugal T2 spectra reflect the complex pore assemblages in oil shales. The small pore realms determine the microscopic complexity, while large pore realms control the macroscopic reservoir quality of oil shales. However large pore realms (interparticle pores and micro-fractures) are not self-similar with the small pore realms, and can't be described by fractal dimension. Fractal analysis gives insights in the heterogeneous assemblage of pore systems and helps describe complexity of pore structure.

Tenderness improvement of reduced-fat and reduced-salt meat gels as affected by high pressure treating time

This study investigated the effect of high-pressure treating time (HPTT) on the tenderness of reduced-fat reduced-salt (RFRS) meat gels. The result of shear force value showed that the RFRS meat gels exhibited excellent tenderness treated with 200 MPa for 3 min. The mechanism of tenderness enhancement was revealed from the perspective of water migration characteristics in meat batters. After HPP, the characteristics of water molecules in meat batters were investigated using low-field nuclear magnetic resonance (LF-NMR) T2 relaxometry. The datas of T2 relaxation time and peak area indicated the free water changed into immobilized water significantly. The result of principal components analysis showed that the sample treated with a proper HPPT (3 min) was significantly different from the others. The tenderness of RFRS meat gel products was improved with the application of 200 MPa, especially treated with 3 min. The improvement of tenderness could be ascribed to the increase of immobilized water. The possible increase of the diameter in three-dimensional gel network might lead to more water molecules entrapped.