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Low-field (LF) nuclear magnetic resonance (NMR) is a very versatile technique that has increasingly shown its value, especially in research involving crude oil. In the field of viscosity and American Petroleum Institute (API) gravity research, physicochemical properties are of great interest to the industry because the first parameter can be an obstacle for production, whereas the latter is used to assess and market the product. Thus, models of viscosity and API gravity were developed in the state of Espı́rito Santo using the transverse relaxation time (T 2 ) and relative hydrogen index (RHI) of postsalt crude oil. The models showed a good degree of reliability for 50 samples (R 2 > 0.96) with viscosity ranging from 23.75 to 1801.09 mPa·s and API gravity from 16.8 to 30.6. A set of more than 15 "unknown" samples was used for validation, with values calculated by the API and viscosity compared to those obtained by the American Society for Testing and Materials (ASTM) 7042-04 standards. Finally, this study proposes a new way to classify oil through T 2 and RHI with the possibility of simultaneously estimating the aforementioned physicochemical properties on the basis of a single quick and reliable measurement.

The exploration of new reservoirs of oil offshore in Brazil shows that the oil has different physical properties, which significantly influence the yield and quality of production. In this sense, principal component analysis (PCA), linear discriminant analysis (LDA), and hierarchical cluster analysis (HCA) chemometric tools were successfully used to correlate the characterization properties of oils with nuclear magnetic resonance (NMR) data. A total of 48 crude oil samples from Brazil were grouped in relation to the origin, that is, fields and reservoirs of pre- and post-salt. Results of the first principal component (PC1) versus the second principal component (PC2) make up for 97.2%, a value considered satisfactory to explain the variability of samples in fields and reservoirs with HCA and LDA. The present study also showed that the transverse relaxation time obtained from low-field nuclear magnetic resonance (LF-NMR) can predict kinematic viscosity in the range of 21–1892 mm2 s–1 and American Petroleum Institute (API) gravity between 17° and 29.4°, thus allowing for the classification of the 48 samples of Brazilian crude oil into medium and heavy. Besides, the oils were identified in relation to their origin. The present study describes a novel methodology to obtain the “chemical signature” of crude oil of different fields and reservoirs.

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This paper reports the droplet size distribution (DSD) measurements in 28 W/O (water/oil) crude oil emulsions prepared with two Brazilian oils (medium and heavy) under different shear conditions using both 10 g L-1 NaCl solution and water production by low field nuclear magnetic resonance (NMR, 2.2 MHz). The PFGSTE (pulsed-field gradient-stimulated echo) pulse sequence applied was able to separate the crude oil emulsion signal for both medium and heavy oil even for low dispersed phase content (1.51 wt.%) and took into account only the aqueous phase signal. All emulsions exhibited an average diameter smaller than 5.5 μm because of the severe shear conditions. Despite the difficult processing of the S24 (6.48 wt.%) emulsion signal, good agreement was achieved between low field NMR and low-angle laser light scattering (LALLS) results. Finally, the paramagnetic ions in the water production did not affect the NMR measurements, demonstrating its applicability for analyzing real emulsions.