The objectives of upgrading oil sands bitumen are:

  1. Reduce viscosity so that product can be pipelined to a refinery without building a costly above-ground upgrading plant, which requires water and auxiliary fuel such as natural gas.

  2. Reduce the cost and amount of upgrading required in the refinery.

  3. Reduce the amount of sulfur, nitrogen, and heavy metals which cause problems with refining catalysts, since these elements tend to concentrate in the heaviest molecules, which end up in the coke.

  4. Sequester the coke in the ground. In-situ upgrading is also desirable for oil shale.

There have previously been reports that upgrading occurs during pyrolysis, but it has not been clear what conditions lead to upgrading. Low temperature (300-350 °C) is economically desirable to minimize cost for RF electric heating of deposits, yet there have been suggestions that low temperature favors coke formation. Both physical and chemical variables affect upgrading, and we attempt to explain these complications.

In the following, pyrolysis experimental methods and data are reviewed. Reaction kinetic models to represent the data are reviewed, and used to calculate low temperature product distributions. These results are replotted as product distillation curves and interpreted to show how upgraded product can be produced. Models indicate that coke is formed after a sequence of reaction steps, so its appearance is slow. Therefore light product can be harvested early, before material reacts further producing excessive coke. Data on Western US oil shale are also reviewed and similar conclusions are drawn. Further reservoir engineering studies are needed to optimize production of light oil.

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