Dispersion properties of NMR relaxation for crude oil

Abstract

Special requirements for design of tools used for wireline NMR logging and NMR logging while drilling and for interpretation model are demanded due to the dispersion properties of NMR relaxation for crude oil. NMR longitudinal relaxation time (T)) and transverse relaxation time (T z ) of the dead oil samples with different viscosities were measured by NMR spectrometers with a Larmor frequency of 2 MHz and 23 MHz at five different temperatures respectively. The results showed that T) was obviously dependent on the Larmor frequency of NMR spectrometer. The degree of T) dispersion became stronger with the increasing crude oil viscosity, Larmor frequency and the viscosity/temperature ratio. T z was independent of NMR spectrometer measuring frequency. It is suggested that the resonance frequency should be selected lower than 2 MHz when measuring T) in logging while-drilling and that T) dispersion should be corrected when Larmor frequency is higher than 2 MHz.

Nuclear Magnetic Resonance Dispersion of Distributions as a Probe of Aggregation in Crude Oils

“…Prior studies of crude oil relaxation at different magnetic fields did not consider this effect. 12,13 The NMRDD technique was developed precisely in order to study such heterogeneous systems characterized by dispersive behavior of relaxation distributions. Interestingly, the appearance of dispersion in the NMRDD profile is not simply a result of high viscosity.…”

“…In such a case, the relaxation distributions show a much more complex dispersion behavior than a uniform shift of the entire distribution; the actual shape of the distribution, not just its mean or peak, changes with varying Larmor frequency. Prior studies of crude oil relaxation at different magnetic fields did not consider this effect. , The NMRDD technique was developed precisely in order to study such heterogeneous systems characterized by dispersive behavior of relaxation distributions.…”

“…A similar approach has been used before to study water in natural soils, but only a uniform shift in the distributionsand no change in their shapewas observed. The temperature dependence of crude oil relaxation properties was studied at a limited range of Larmor frequencies (2–80 MHz), , but systematic analysis of the dispersion (i.e., relaxation as a function of frequency) was not attempted. NMRDD has no limitations on the sample opacity or optical density, it is noninvasive and nondestructive, and it can be used to monitor aggregation in situ inside the native fluid and in principle also inside a porous medium.…”

Chapter 7. Estimating Chemical and Microstructural Heterogeneity by Correlating Relaxation and Diffusion

“…Assuming a ground truth, forward simulation of Eq. 6 is commonly used to evaluate precision and accuracy of the inversion 63,173 . For more complex scenarios, such as the presence of restrictions, various approaches have been developed.…”

Pore-scale investigation of residual oil displacement in surfactant–polymer flooding using nuclear magnetic resonance experiments

“…Therefore, there is usually a discrepancy between simulation results and actual conditions (Li et al 2006). Nuclear magnetic resonance (NMR) is a quick, accurate, non-destructive, and widely used technology for core testing (Kleinberg and Vinegar 1996;Xie and Xiao 2007;Zhao et al 2011). In NMR measurements, the received signals originate only from fluids in pores.…”