Evaluation of the Physicochemical Properties of the Postsalt Crude Oil for Low-Field NMR

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 (<i>T</i>₂) and relative hydrogen index (RHI) of postsalt crude oil. The models showed a good degree of reliability for 50 samples (<i>R</i>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 <i>T</i>₂ and RHI with the possibility of simultaneously estimating the aforementioned physicochemical properties on the basis of a single quick and reliable measurement