“…From 13 C measurements, it was concluded that when compared to the light oils under investigation, a small decrease in the concentration of aliphatic groups was observed in Ashalchinskoe oil, while, on the other hand, the concentration of aromatic groups is about 3–4 times higher. Additionally, it should be noted that the parameter of the ratio T 1 / T 2 that is usually used for correlation with viscosity is of the order ∼20 for the highest intensity peak and ∼250 for the peak with lower intensity and shorter T 2 values, resulting in a mean value of T 1 / T 2 ≈ 60. Despite the high viscosity (see Table ) at ambient temperature and the relatively high content of asphaltenes, no components with T 1 / T 2 ≈ 1000 are common for bitumen, heavy oils, and kerogen were observed.…”
The presence of paramagnetic
species such as vanadyl complexes
(VO2+) and free carbon radicals in petroleum disperse systems
(PDSs) such as crude oil, bitumen, or kerogen causes significant interest
of studying the structure of PDS, high-molecular weight components,
and their effects on the physical and chemical properties of PDS products
by magnetic resonance techniques. However, the lack of detailed studies
keeps the exact structure, aggregation mechanism, and interaction
with complex composites of the PDS still disputable. In this contribution,
detailed electron paramagnetic resonance (EPR) and nuclear magnetic
resonance (NMR) investigations, including advanced fast field cycling
dynamic nuclear polarization, of heavy crude oil focused on vanadyl
complexes are presented. A perceptible room-temperature 1H dynamic nuclear polarization (DNP) solid effect at the X-band (magnetic
field of 300–400 mT corresponding to the EPR frequency of 9.5
GHz and NMR frequency of 14.6 MHz), with enhancement ±5, is observed
at moderate microwave irradiation power in crude oil with a high concentration
of VO2+, while no Overhauser DNP contribution is found.
Using NMR T
2-encoding, DNP spectra and
molecular dynamics, two components are distinguished, from which the
one with slower dynamics exhibits higher DNP enhancement via VO2+ complexes. The observed difference is discussed in terms
of electron–nuclear interaction and relative parts of hyperpolarized
nuclear spins using an advanced model for DNP data simulation.
“…From 13 C measurements, it was concluded that when compared to the light oils under investigation, a small decrease in the concentration of aliphatic groups was observed in Ashalchinskoe oil, while, on the other hand, the concentration of aromatic groups is about 3–4 times higher. Additionally, it should be noted that the parameter of the ratio T 1 / T 2 that is usually used for correlation with viscosity is of the order ∼20 for the highest intensity peak and ∼250 for the peak with lower intensity and shorter T 2 values, resulting in a mean value of T 1 / T 2 ≈ 60. Despite the high viscosity (see Table ) at ambient temperature and the relatively high content of asphaltenes, no components with T 1 / T 2 ≈ 1000 are common for bitumen, heavy oils, and kerogen were observed.…”
The presence of paramagnetic
species such as vanadyl complexes
(VO2+) and free carbon radicals in petroleum disperse systems
(PDSs) such as crude oil, bitumen, or kerogen causes significant interest
of studying the structure of PDS, high-molecular weight components,
and their effects on the physical and chemical properties of PDS products
by magnetic resonance techniques. However, the lack of detailed studies
keeps the exact structure, aggregation mechanism, and interaction
with complex composites of the PDS still disputable. In this contribution,
detailed electron paramagnetic resonance (EPR) and nuclear magnetic
resonance (NMR) investigations, including advanced fast field cycling
dynamic nuclear polarization, of heavy crude oil focused on vanadyl
complexes are presented. A perceptible room-temperature 1H dynamic nuclear polarization (DNP) solid effect at the X-band (magnetic
field of 300–400 mT corresponding to the EPR frequency of 9.5
GHz and NMR frequency of 14.6 MHz), with enhancement ±5, is observed
at moderate microwave irradiation power in crude oil with a high concentration
of VO2+, while no Overhauser DNP contribution is found.
Using NMR T
2-encoding, DNP spectra and
molecular dynamics, two components are distinguished, from which the
one with slower dynamics exhibits higher DNP enhancement via VO2+ complexes. The observed difference is discussed in terms
of electron–nuclear interaction and relative parts of hyperpolarized
nuclear spins using an advanced model for DNP data simulation.
“…Straley et al [6] and Morris et al [7], based on an analysis of 66 stock crude samples and viscosity standards, established the following correlation between log-mean relaxation time and dynamic viscosity at ambient temperature, often called Morriss correlation (here and below the relaxation time, , is in seconds, viscosity, , is in cP and temperature, is in K and the appropriate units of prefactors apply):The very similar form of an equation, which includes a temperature term, was proposed by Vinegar [8]:Zhang [9] arrived an expression which generally combines the two correlations above for hydrocarbons saturated with air:and for degassed oxygen-free alkanes:However, there is a discrepancy in literature regarding Eq. 5 in whether it applies to air-saturated hydrocarbons (Zhang et al [9]) or relates to oxygen-free state (Deng et al [28]).Fig. 1Comparison of experimental relaxation-normalised viscosity data of n -alkanes at arbitrary temperature to published sets, both in oxygen-free and air-saturated states (see Tables 1 and 2)
…”
Section: Correlation Of Diffusivity Viscosity and Nmr Relaxationmentioning
Nuclear magnetic resonance (NMR) diffusion-relaxation correlation experiments (D-) are widely used for the petrophysical characterisation of rocks saturated with petroleum fluids both in situ and for laboratory analyses. The encoding for both diffusion and relaxation offers increased fluid typing contrast by discriminating fluids based on their self-diffusion coefficients, while relaxation times provide information about the interaction of solid and fluid phases and associated confinement geometry (if NMR responses of pure fluids at particular temperature and pressure are known). Petrophysical interpretation of D- correlation maps is typically assisted by the “standard alkane line”—a relaxation-diffusion correlation valid for pure normal alkanes and their mixtures in the absence of restrictions to diffusing molecules and effects of internal gradients. This correlation assumes fluids are free from paramagnetic impurities. In situations where fluid samples cannot be maintained at air-free state the diffusion-relaxation response of fluids shift towards shorter relaxation times due to oxygen paramagnetic relaxation enhancement. Interpretation of such a response using the “standard alkane line” would be erroneous and is further complicated by the temperature-dependence of oxygen solubility for each component of the alkane mixture. We propose a diffusion-relaxation correlation suitable for interpretation of low-field NMR D- responses of normal alkanes and their mixtures saturating rocks over a broad temperature range, in equilibrium with atmospheric air. We review and where necessary revise existing viscosity-relaxation correlations. Findings are applied to diffusion-relaxation dependencies taking into account the temperature dependence of oxygen solubility and solvent vapour pressure. The effect is demonstrated on a partially saturated carbonate rock.
“…DEFIR pulse sequence is an optimization of the DEFSR pulse sequence (Deng 2014). It replaces the FSR part of DEFSR pulse sequence into FIR sequence.…”
Tremendous progress of developing nuclear magnetic resonance (NMR) fluid analyzer has been witnessed in the oil industry for last two decades. This device allows extensive and accurate exploration of fluid properties, such as its hydrogen content, composition, viscosity, hydrogen index (HI), mud filtrate invasion, gas to oil ratio, average velocity, velocity distribution etc., in the situations of in situ downhole or surface Petro-pipelines. In this review article, we focus on the design principle, manufacturing, implementation, methodology and applications of NMR fluid analyzer to oil and gas industry. A detailed description of the state-of-art NMR fluid analyzers was firstly given to exhibit their respective characteristics. With these experiences on hand, we introduced a series of NMR fluid analyzers designed by us at China University of Petroleum-Beijing with continuous optimizations, in terms of magnet construction, antenna layout, circuit design and operating surroundings. These systems discussed in this article have been demonstrated to achieve multiple NMR parameter acquisition when the fluid is in stationary or flowing state. In the end, a prototype was fabricated and validated considering a vast of engineering influences, such as variable temperatures in a large range, high pressure, limited volume, detection efficiency, etc. A particular emphasis of this paper is to expedite the measurement efficiency of the NMR fluid analyzer to reduce the operation costs. This dilemma can be Figured out by upgrading both pulse sequence and observational mode. For different fluid states, two rapid pulse sequences were proposed to sufficiently obtain the multi-dimensional NMR correlation map. Meanwhile, two observational modes were developed to take full advantage of the polarization time, during which the individual antenna was systematically switched. Another domain of interest in this review concerns the applications of this new tool. For stationary fluids case, accurate identification of fluid properties is of great value for scheme building in oil and gas exploration process. Particularly, it can acquire the fluid content by different NMR responses of different components. In addition, with Bloembergen theory and Stokes–Einstein equation, not only molecular dynamics and composition, but also oil viscosity can be readily evaluated. Moreover, HI information of crude oils will be speculated through partial least square regression. As for flowing fluids case, velocity is a significant parameter to understand the in situ fluid exploitation and therefore evaluate the productivity of certain oil wells or pipelines. Regarding to the unique magnet and antenna designs in our NMR fluid analyzer; this review adopts two distinct methods to obtain flow velocity at a wide rating scale. The first one is a time-of-flight method adaptive in a homogeneous magnetic field, which is suitable in the case of fluid at high flow velocity. The other one relies on the adjacent echo phase difference at a magnetic field with constant gradient, which is preferred for relatively low flow velocity. In the near future, this tool will be tested underground to offer individual fluid velocities by combining both the stationary and flowing analysis methods.
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