Nuclear Magnetic Resonance Behavior Research Articles

Influencing mechanics and correction method of nuclear magnetic resonance measurement in igneous rocks reservoir

Nuclear magnetic resonance (NMR) measurement provides lithology-independent porosity and pore structure for sedimentary reservoirs. Recently, oil and gas were discovered in igneous rock formations, however, NMR logging porosity is substantially lower than the true porosity, and the T2 distributions does not characterize the pore-size distributions. These observations limit the use of NMR logging in igneous rock formations and new research is needed to be developed. To address this gap in the literature, using numerical simulation of NMR behavior, we conduct a theoretical study to examine the impact of magnetic susceptibility, echo spacing, and fluid type on the T2 distributions in igneous rock. The simulation results and laboratory experiment show that, the paramagnetic minerals affect the magnetization of fluids in pores and rate of the echo decay, and NMR porosity is thus significantly reduced. To effectively correct the NMR measurement, a new approach is proposed to improve the underestimation of NMR porosity and T2 distribution shifting to shorter times. For a pore model, the corrected porosity and T2 distribution are both in good agreement with the model. In a case study from Chepaizi area of Junggar Basin, China, the corrected NMR porosity matches well with core measurement, and the corrected T2 distribution shifts to longer times more than before. Moreover, bound fluid volume and movable fluid volume are both corrected, and the NMR permeability also agrees well with core laboratory measurement, which proves that the correction method effective. Therefore, this technology enables NMR log for evaluating the igneous rock reservoir quality.

Syntheses of Chiral Phosphazenes with Stereogenic Centers: NMR Behavior in the Presence of a Chiral Solvating Agent

ABSTRACTThe condensation reactions of tetrachloro mono (1 and 2) and bisferrocenyl spirocyclotriphosphazenes (3–5) with morpholine in tetrahydrofuran gave the partly morpholino‐substituted ferrocenylphosphazenes. When the reactions were carried out with equal amounts of 1–5 and morpholine, the mono‐substituted ferrocenylphosphazenes (1a, 3a–5a) formed as the major product. While the reactions were made with 1 equiv of 1–5 and 2 equiv of morpholine, the corresponding geminal–phosphazenes (1b–5b) were isolated. In addition, the condensation reactions of 1 equiv of 1–5 and 3 equiv of morpholine resulted in the formation of di‐(1b–5b), tri‐(2c–5c), and tetra‐substituted phosphazenes. The tri‐substituted compounds were isolated as major products. Some new phosphazenes have stereogenic P center(s). The stereogenic properties of 1a and 2c were investigated using 31P nuclear magnetic resonance (NMR) spectroscopy in the presence of the chiral solvating agent; (S)‐(+)‐2,2,2‐trifluoro‐1‐(9′‐anthryl)ethanol. The structures of all the phosphazenes were characterized by one‐dimensional 1H, 13C, and 31P NMR, and two‐dimensional heteronuclear single quantum coherence spectral data. The salient spectral properties of the phosphazenes were presented.

Characterization of the phase transitions of ethyl substituted polyhedral oligomeric silsesquioxane

This study describes the synthesis and molecular mobility of both partially deuterated and fully protonated ethyl polyhedral oligomeric silsesquioxane (POSS) crystals. The primary phase transitions were identified with differential scanning calorimetry at ∼257 and ∼253 K for partially deuterated and fully protonated ethyl POSS, respectively. A change in entropy between ∼47 and 28 ± 2 J mol −1 K −1 was observed for these transitions. At high temperature the unit cells are rhombohedral, while triclinic unit cells are observed at temperatures below the phase transition point. The crystallographic transition to the low temperature phase, 110 K, is marked by an abrupt increase in density (1.31 to 1.43 ± 0.05 g cm −3) and decrease in symmetry ( R-3 to P-1). Additionally, the crystallographic transition results in abrupt changes in the spin lattice relaxation and linewidth as detected with solid-state proton nuclear magnetic resonance (NMR) spectroscopy. This NMR behavior suggests a transition in molecular mobility of both ethyl derivatives. Both POSS derivatives exhibit an increase in correlation time and activation energy. For deuterated ethyl POSS, the motions became increasingly anisotropic after the temperature is lowered past its transition point.

Nuclear-magnetic-resonance interaction mechanism in Rb2CoCl4 single crystals with the electric magnetic type

The Rb87 spin-lattice relaxation time of Rb2CoCl4 single crystals grown using the slow evaporation method was measured using nuclear magnetic resonance. The recovery trace for the central line of Rb87 with dominant magnetic relaxation cannot be represented with a single exponential function, but can be represented with a linear combination of two exponential functions. The change in the Rb87 spin-lattice relaxation rate near Tc1 corresponds to the ferroelectric to incommensurate phase transition. There is a weak anomalous contribution to T1, and this seems to be the only detectable influence of a structural phase transition. The temperature dependence of T1−1 near Ti is more or less continuous and is not affected by the normal-incommensurate phase transition. For T>Ti, the spin-lattice relaxation rate is governed by molecular motion as described by the Bloembergen-Purcell-Pound theory. This behavior is different to that found for Rb in Rb2ZnCl4. The phase-transition temperatures of the Rb2CoCl4 and Rb2ZnCl4 single crystals are quite similar, but their phase-transition mechanisms are different. The nuclear-magnetic-resonance (NMR) interaction mechanism in Rb2ZnCl4 is well known to be of the electric quadrupolar type whereas in Rb2CoCl4 it is of magnetic origin. Therefore a completely different NMR behavior is obtained in the two crystals.

2003 Nobel Prize in physics for theoretical work on superfluid 3He.

The element helium comes in two (stable) forms, 4He and 3He; at low temperatures and pressures both form liquids rather than solids. The liquid phase of the common isotope, 4He, was realized nearly a century ago, and since 1938 has been known to show, at temperatures below about 2K, the property of superfluidity--the ability to flow through the narrowest capillaries without apparent friction. The light isotope, 3He, is believed to be of quite a different nature; however, because of its similarity to the electrons in metals, which at low temperatures sometimes form "Cooper pairs" and thereby become superconducting, theorists in the 1960s and early 1970s had speculated that something similar might happen in liquid 3He, which would then also show superfluidity though for reasons rather different than 4He. In 1972 nuclear magnetic resonance (NMR) experiments at Cornell University revealed the existence, below 3 millidegrees, if two new phases, one of which displayed extraordinary NMR properties. Anthony Leggett is one of the theorists who succeeded in fitting the experimental properties into the "Cooper-pairing" scenario; in particular, he explained the NMR behavior and predicted further novel NMR phenomena which were subsequently found.

1H MAS and 1H --> 31P CP/MAS NMR study of human bone mineral.

Chemical structure of human bone mineral was studied by solid-state nuclear magnetic resonance (NMR) with magic-angle spinning (MAS). Trabecular and cortical bone samples from adult subjects were compared with mineral standards: hydroxyapatite (HA), hydrated and calcined, carbonatoapatite of type B with 9 wt% of CO3(2-) (CHA-B), brushite (BRU) and mixtures of HA with BRU. Proton spectra were acquired with excellent spectral resolution provided by ultra-high speed MAS at 40 kHz. 2D 1H-31P NMR heteronuclear correlation was achieved by cross-polarization (CP) under fast MAS at 12 kHz. 31P NMR was applied with CP from protons under slow MAS at 1 kHz. Appearance of 31P rotational sidebands together with their CP kinetics were analyzed. It was suggested that the sidebands of CP spectra are particularly suitable for monitoring the state of apatite crystal surfaces. The bone samples appeared to be deficient in structural hydroxyl groups analogous to those in HA. We found no direct evidence that the HPO4(2-) brushite-like ions are present in bone mineral. The latter problem is extensively discussed in the literature. The study proves there is a similarity between CHA-B and bone mineral expressed by their similar NMR behavior.

A new nuclear magnetic resonance algorithm to determine equilibrium constants of the species in the B(III)–H 2O system

Several efforts have been attempted to study species formation by Nuclear Magnetic Resonance (NMR) in systems with several chemical equilibria present. The majority of these are qualitative and only a few have tried to relate component fractions of a distribution diagram with experimental area fractions determined from NMR spectra to obtain equilibrium constants values. In this work we present a new focus that attempts to relate the species concentration fractions in the system with area fractions beneath NMR peaks to achieve this task. 11B-NMR data of B(III)–H 2O systems have been processed with the aid of formation constant values (−log * β) obtained by potentiometry which are 9.17±0.01 for B(OH) 3, 9.79±0.08 for B 2O(OH) 5 −, 19.90±0.09 for B 3O 3(OH) 4 − and 38.50±0.04 for B 5O 6(OH) 4 −, form B(III)–H 2O systems with 0.075 M≤[B(III)] total≤0.700 M, in agreement with previous reports and NMR behavior. The treatment of NMR data developed in this work gives a new methodology to obtain formation constants and suggests the possibility to establish a generalization of Beer's law to NMR spectroscopy.

Nuclear magnetic resonance of J-coupled quadrupolar nuclei: Use of the tensor operator product basis

In nuclear magnetic resonance (NMR) of I=1/2 nuclei that are scalar coupled to quadrupolar spins, a tensor operator product (TOP) basis set provides a convenient description of the time evolution of the density operator. Expressions for the evolution of equivalent I=1/2 spins, coupled to an arbitrary spin S>1/2, were obtained by explicit algebraic density operator calculations in Mathematica, and specific examples are given for S=1 and S=3/2. Tensor operators are described by the convenient quantum numbers rank and order and this imparts to the TOP basis features that enable an intuitive understanding of NMR behavior of these spin systems. It is shown that evolution as a result of J coupling alone changes the rank of tensors for the coupling partner, generating higher-rank tensors, which allow efficient excitation of S-spin multiple-quantum coherences. Theoretical predictions obtained using the TOP formalism were confirmed using multiple-quantum filtered heteronuclear spin-echo experiments and were further employed to demonstrate polarization transfer directly to multiple-quantum transitions using the insensitive nucleus enhancement by polarization transfer pulse sequence. This latter experiment is the basis of two-dimensional heteronuclear correlation experiments and direct generation of multiple-quantum S-spin coherences can therefore be exploited to yield greater spectral resolution in such experiments. Simulated spectra and experimental results are presented.

6Li Magic Angle Spinning NMR Study of the Cathode Material LiNixMn2 − x O 4 : The Effect of Ni Doping on the Local Structure during Charging

magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy has been used to study the local structure of synthesized by solid-state reactions. When the extent of doping is small and 0.1), several resonances are observed, which are assigned to lithium local environments containing different numbers of and ions. As the doping level increases and the average manganese oxidation state rises, the intensity of the resonances assigned to lithium environments containing a greater number of higher-oxidation state manganese ions increases; this results in a gradual shift of the center of mass of the spectrum to higher frequency. By only ions are present, and only one major resonance, due to the lithium local environment is observed; this is consistent with Mn/Ni ordering on the octahedral sites of the spinel structure. The variable temperature NMR behavior of these samples is indicative of different magnetic behavior for the undoped and doped materials. A plot of shift) vs. temperature is consistent with the predominance of antiferromagnetic correlations for low doping level samples, while antiferromagnetic correlations clearly dominate the behavior of the sample, resulting in overall ferrimagnetic behavior. spectra were also collected following various levels of charging. In the case of is deintercalated from the different local sites sequentially: lithium ions in the local environment containing manganese ions with an average oxidation state of +3.5 are deintercalated first, followed by lithium ions in sites containing progressively more ions. In contrast, for where the deintercalation process involves oxidation of only, no changes in the lithium local environments were observed during the charging process: the shift position remained constant during the charging cycle and only a loss of the intensity of the lithium signal was observed. © 2001 The Electrochemical Society. All rights reserved.

7Li and 31P nuclear magnetic resonance studies of Li1−3xMgFexPO4

We report a 7Li and 31P nuclear magnetic resonance (NMR) study in the Li1−3xMgFexPO4 phases between 150 and 410 K. This study, complementary to those made using Mössbauer and magnetic neutron diffraction experiments, confirms that the Fe ions enter as Fe(III) in the lattice, and that they enter substituting Li ions. Ionic conductivity measurements, together with the NMR behavior of the 7Li and 31P NMR spectra show that no Li mobility occurs in the temperature range studied even with the addition of the Fe impurity.

Conformational study of 2-phenylbenzothiazine part of SA2995, a Ca 2+ antagonist having a benzothiazine skeleton, and structure-activity relationships

Nuclear magnetic resonance (NMR) studies were carried out for the title compound ((±)-3,4-dihydro-2-[5-methoxy-2-[3-[ N-methyl- N-[2-(3,4-methy ( 1a; R = H) and its 2-substituted analogs ( 1b; R = OCH 3, 1c; R = SCH 3, 1d; R = CH 3, 1e; R = i-C 3H 7) which had Ca 2+ activities. Conformational analysis using the model compounds of the 2-phenylbenzothiazine (2-PBT) part of 1 by semiempirical molecular orbital method agreed with the NMR behavior. Two local minimum conformations, having different rotational angles (θ1) of the 2-phenyl ring, were suggested for biologically active 1a–1d. The molar fractional ratios, including the conformations within a particular θ1 range that contained each global minimum conformation, were found to correlate well with the activities. In the same θ1 range, any stable conformation was not indicated for non-active compound 1e. From these results, the active conformation for the 2-PBT part of 1 was suggested to be similar to the global minimum conformation indicated for the most potent 1a.

ChemInform Abstract: SOLID‐STATE NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY OF MINERALS

Nuclear magnetic resonance (NMR) spectroscopy has been a useful tool for examining the structure of molecules in solution since the 1950s. It has only been since the late 1970s and early 1980s, though, that developments in very high field superconducting magnets and magic-angle sample-spinning (MASS) have made NMR routinely useful for examining the structure of solids. In this paper, we briefly review the theory of MASS NMR spectroscopy and some of the recent experimental results for minerals. N MR spectroscopy examines the local structural environment of atoms, to at most the third and fourth nearest neighbors. For crystalline silicates, silicon-29 and aluminum-27 MASS NMR have already proven useful in examining the validity of the aluminum avoidance principle and the extent of Al(4)/Si order/disorder, in determining the extent of polymerization, in determining the number of crystallographically distinct silicon sites present, in estimating bond strength sums and Si-O-(Si, AI) bond angles, and in detecting the presence of Al(4) and Al(6) and estimating Al(4)/Si and Al(6)/Al(4) ratios. As the NMR behavior of more nuclides (certainly including boron-H, nitrogen-IS, oxygen-17, fluorine-19, sodium-23, magnesium-25, and phosphorus-31) becomes better understood, we feel that this method will become a powerful tool for examining the local structural environment of a wide variety of species in a broad range of

SOLID-STATE NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY OF MINERALS

Nuclear magnetic resonance (NMR) spectroscopy has been a useful tool for examining the structure of molecules in solution since the 1950s. It has only been since the late 1970s and early 1980s, though, that developments in very high field superconducting magnets and magic-angle sample-spinning (MASS) have made NMR routinely useful for examining the structure of solids. In this paper, we briefly review the theory of MASS NMR spectroscopy and some of the recent experimental results for minerals. N MR spectroscopy examines the local structural environment of atoms, to at most the third and fourth nearest neighbors. For crystalline silicates, silicon-29 and aluminum-27 MASS NMR have already proven useful in examining the validity of the aluminum avoidance principle and the extent of Al(4)/Si order/disorder, in determining the extent of polymerization, in determining the number of crystallographically distinct silicon sites present, in estimating bond strength sums and Si-O-(Si, AI) bond angles, and in detecting the presence of Al(4) and Al(6) and estimating Al(4)/Si and Al(6)/Al(4) ratios. As the NMR behavior of more nuclides (certainly including boron-H, nitrogen-IS, oxygen-17, fluorine-19, sodium-23, magnesium-25, and phosphorus-31) becomes better understood, we feel that this method will become a powerful tool for examining the local structural environment of a wide variety of species in a broad range of