Abstract:

The crude oil is of broad distributions of NMR relaxation for their complex components and changeable viscosity. It is important for interpretation of NMR logging to distinguish the oil and water formations to study on the crude oil NMR relaxation properties changing with different viscosity, work ing frequency and echo spacing TE. The dead oil NMR relaxation times are measured with two working frequency (2 Hz and 23MHz) NMR spectrometers in this paper. The results show that, light oil has similar T₁and T₂, and inversely proportional to viscosity, viscosity/temperature in logarithmic coordinates. However, heavy oil has greater T₁ than T₂,T₁/ T₂ is increasing as the increases of working frequency and viscosity/temperature. The relaxation time of light oil is not sensitive to the working frequency of the NMR spectrometer. Heavy oil relaxation time is related with working frequency. For heavy crude oil, apparent T2 relaxation time increases and the signal amplitude decreases as increasing echo spacing TE

Key words: NMR, relaxation properties, working frequency, crude oil, viscosity