Using Low-Field NMR to Understand Fines Behaviour
Hum, F. and Kantzas, A.
SCA2005-46, presented at the 2005 International Symposium of the Society of Core Analysts, held in Toronto, Ontario, Canada, August 21-25, 2005.
An increasing amount of the oil recovered today originates from oil sands. The recovery efficiency from oil sands is dependent on the fines content, however the relationship between fines content and oil recovery is not well understood. This paper proposes using low field nuclear magnetic resonance (NMR) as a tool to understand the correlation between the grade of the ore (i.e., the degree of ease to separate oil from the sand) and the fines content. First, synthetic samples with different clay, sand, brine and heavy oil contents were created to simulate ores of varying recovery grades. The NMR results showed that brine in montmorillonite is distinct from brine in illite or kaolinite, a fact that could be exploited in using NMR for clay identification. The results from the synthetic samples were used to create nomographs correlating NMR parameters and clay content.
Second, field ore samples underwent Dean-Stark extraction and the solids were resaturated and re-measured in the NMR. The results were compared to those obtained from synthetic samples with similar compositions and it appears the results from the two types of samples are similar, despite having significantly different particle size distributions. This work shows that it is possible to determine fines content from NMR. Upon creating a more general model, these findings may be used towards determining clay type and content from NMR logs. This information may also be used towards refining the cut-off method for more accurately determining oil reserves.