Understanding oil sand structure and recovery processes at the laboratory scale is important for generating accurate models to predict performance ‘in the field’. Magnetic resonance imaging and nuclear magnetic resonance (NMR) are powerful nondestructive, non-invasive tools that have been shown to be ideal for characterizing porous materials. Previous work using NMR to investigate heavy oil and bitumen sands has primarily focused on one-dimensional relaxation analysis. Whilst the spectra produced are sensitive to the confining geometry and fluid types, there is often overlap between relaxation peaks from different fluids with similar relaxation times. These peaks are often difficult to separate accurately. We present a 20 MHz, 1H NMR two-dimensional correlation spectroscopy study of a range of synthetic oil sands systematically prepared with varying compositions of bitumen, water, sand and clay.
These two-dimensional experiments couple nuclear spin relaxation or self-diffusion in one time period with relaxation or self-diffusion occurring during a subsequent time period. This results in the acquisition of proton population distributions as a function of longitudinal (T1) relaxation time and transverse (T2) relaxation time. This allows further, more accurate, discrimination of the fluids and their different physical environments within in the oil sands. The results can also potentially lead to improved wettability and viscosity analyses of heavy oils in-situ.
The results from the synthetic samples are then applied to natural core samples.