title: Molecular dynamics and composition of crude oil by low-field nuclear magnetic resonance.
abstract: Nuclear magnetic resonance (NMR) techniques are widely used to identify pure substances and probe protein dynamics. Oil is a complex mixture composed of hydrocarbons, which have a wide range of molecular size distribution. Previous work show that empirical correlations of relaxation times and diffusion coefficients were found for simple alkane mixtures, and also the shape of the relaxation and diffusion distribution functions are related to the composition of the fluids. The 2D NMR is a promising qualitative evaluation method for oil composition. But uncertainty in the interpretation of crude oil indicated further study was required. In this research, the effect of each composition on relaxation distribution functions is analyzed in detail. We also suggest a new method for prediction of the rotational correlation time distribution of crude oil molecules using low field NMR (LF-NMR) relaxation time distributions. A set of down-hole NMR fluid analysis system is independently designed and developed for fluid measurement. We illustrate this with relaxation-relaxation correlation experiments and rotational correlation time distributions on a series of hydrocarbon mixtures that employ our laboratory-designed downhole NMR fluid analyzer. The LF-NMR is a useful tool for detecting oil composition and monitoring oil property changes. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China.
authors.forename: Zijian
authors.initials: Z
authors.lastname: Jia
authors.affiliation: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China.
authors.forename: Lizhi
authors.initials: L
authors.lastname: Xiao
authors.affiliation: SINOPEC Research Institute of Petroleum Engineering, Beijing, China.
authors.forename: Zhizhan
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China.
authors.forename: Guangzhi
authors.initials: G
authors.lastname: Liao
authors.affiliation: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China.
authors.forename: Can
authors.initials: C
authors.lastname: Liang
mesh_terms: D000465:Algorithms; D006838:Hydrocarbons / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D000066388:Oil and Gas Industry; D010578:Petroleum / Q000032:analysis*; D013696:Temperature
chemical_list: D006838:Hydrocarbons; D010578:Petroleum
keywords: crude oil; low-field NMR; relaxation; rotational correlation time; two-dimensional nuclear magnetic resonance