Solid-like Component in the Spin-Spin NMR-Relaxation of Heavy Oils

Abstract

The study of row heavy oil samples from Tatarstan and Vietnam oil wells was done by solid-echo nuclear magnetic resonance (NMR) technique on the hydrogen nuclei. For the first time in the oil study, the component with short spin-spin relaxation time (T_2s = 9.8-31.2 ms) and free induction decay (FID) shape similar to a solid one was detected for all oil samples. Density 𝜌, "zero" viscosity 𝜂₀, asphaltene content and solid part P_S of ¹H NMR signal were measured for whole row oil samples. The correlation between the part P_S of ¹H NMR signal and oil density r was found for samples of Tatarstan oil, by the other hand, data for samples of Vietnam oil did not show the correlation. No correlation dependences of the part P_S of ¹H NMR signal and "zero" viscosity 𝜂₀ from asphaltene amount for whole row of oil samples were confirmed, that indicates other crystalline supramolecular structures (more probably, crystalline paraffin) existence in the oil. As a main result, the correlation between oil viscosity and the amount of the solid-like structures in it was found. The significant differences of the solid-echo signal shapes and spin-spin relaxation times of the solid-like structures were obtained for the different oil samples, that demands additional studies.