Summary
Low-field nuclear magnetic resonance (NMR) relaxometry has been used
successfully to perform estimates of oil and water content in unconsolidated
oil-sand samples. This work has intriguing applications in the oil-sands mining
and processing industry, in the areas of ore and froth characterization.
Studies have been performed on a database of ore and froth samples from the
Athabasca region in northern Alberta, Canada. In this paper, new automated
algorithms are presented that predict the oil- and water-weight content of
oil-sand ores and froths.
Suites of real and synthetic samples of bitumen, water, clay, and sand have
also been used to investigate the physical interactions of the different
parameters on the NMR spectra. Preliminary observations regarding spectral
properties indicate that it may be possible in the future to estimate the
amount of clay in the samples, based upon shifts in the NMR spectra. NMR
estimates of oil and water content are fairly accurate, thus enhancing the
possibility of using NMR for oil-sands development and in the oil-sands mining
industry.
Introduction
The oil sands of northern Alberta contain some of the world’s largest
deposits of heavy oil and bitumen. As our conventional oil reserves continue to
decline, these oil sands will be the future of the Canadian oil industry for
years to come and will allow Canada to continue to be a world leader in both
oil production and technology development. Approximately 19% of these bitumen
reserves are found in unconsolidated deposits that lie close enough to the
surface that they can be recovered with surface-mining technology (Alberta
Energy and Utilities Board 2004). In 2003, this translated to 35% of all
heavy-oil and bitumen production (Alberta Energy and Utilities Board 2004), and
numerous companies have invested billions of dollars in oil-sands
mine-development projects. Furthermore, many in-situ bitumen-recovery options
are currently being designed and field tested for recovering oil in deeper
formations (Natl. Energy Board 2004). Being able to predict oil properties and
fluid saturation in situ and process optimization of bitumen extraction
(frothing) is therefore of considerable value to the industry.
There are several areas in oil-sands development operations where it is
important to have an estimate of the oil, water, and solids content of a given
sample. During initial characterization of the reservoir, it is necessary to
determine oil and water content with depth and location in the reservoir.
Fluid-content determination with logging tools would be beneficial for all
reservoir-characterization studies, whether for oil-sands mining or in-situ
bitumen recovery. In mining operations, during the processing of the mined
oil-sand ore, having information about the oil, water, and solids content
during the extraction process will allow for improved process optimization and
control. The industry standard for measuring oil, water, and solids content
accurately is the Dean-Stark (DS) extraction method (Core Laboratories 1992).
This is essentially a distillation procedure, whereby boiling solvent is used
to vaporize water and separate the oil from the sand. Oil, water, and solids
are separated and their contents measured separately. The problem with DS is
that it requires large amounts of solvents and is time consuming. Centrifuge
technology is often used for faster process control, but this can be inaccurate
because of similar fluid densities and the presence of emulsions. New methods
for fast measurements of oil, water, and solids content are needed.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
29 August 2005
- Revised manuscript received:
21 August 2006
- Manuscript approved:
7 September 2006
- Version of record:
20 December 2006
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