Methods for determining in situ the viscosity of heavy oil using nuclear magnetic resonance relaxation time measurements

摘要

The viscosity η (in centipoise) of a heavy oil sample is determined according to an equation of the form ln; $$ \frac{\eta }{{\eta }_g}=\frac{-C1*\left(T-c^{\prime }246\right)}{c^{″}47.10+\left(T-c^{\prime }246\right)},$$where T is the temperature of the heavy oil, T_2LM is the logarithmic mean of the T₂ distribution of the sample obtainable from nuclear magnetic resonance (NMR) measurements, c′=1.0±0.05, c″=1.0±0.04, η_g is the glass transition temperature viscosity of the heavy oil and a function of T_2LM, and C1 is a variable which is a constant for the heavy oil and is a function of T_2LM. Both C1 and η_g are considered functions of certain NMR values associated with the heavy oil sample, with η_g and C1 preferably estimated by empirically fitting data to the equations ln T_2LM=a′+b′ ln η_g and ln T_2LM=a″+b″C1, where a′, b′, a″ and b″ are constants.