In order to enhance extra heavy oils and tar sands recovery, steam injection has become popular as it decreases bitumen viscosity via increase of formation temperature. However, such process comes with some drawbacks such as the necessity to dispose of substantial nearby quantity of water, the impossibility to 100% recycle this water, and the co-generation of a significant quantity of acid gases. Moreover the resulting hydrocarbons are still extra heavy oil/bitumen with all the constraints it implies in terms of pipe transport and refining.
For these reasons, the development of the process of In-Situ Upgrading (IUP) by Subsurface Pyrolysis is debated. The idea would be to sufficiently heat the formation in order to pre-upgrade the oil in-situ; instead of just temporarily decreasing its viscosity. The process can be highly energy consuming but would offer multiple potential advantages such as production of a higher quality product with already a high commercial value, reduction of required infrastructure and expenses on production site for dilution or pre-upgrading before pipe transport, and no use of water, etc.
This study presents the feasibility of such IUP process by performing a core experiment under reservoir conditions. First, a compositional kinetic model is developed in order to correctly predict the products composition during pyrolysis; which is then validated using laboratory data. This is a key element in an IUP process as the results of kinetic model gives an idea of better designing the core experiment, who can properly mimic reservoir behavior. The experimental results are promising in terms of upgraded oil production i.e. light cuts, acid gases, pyrobitumen with proper thermal front propagation. It showed that with time and temperature there will be production of large quantity of light components, light cuts, and while generated pyrobitumen will remain be in the core. This means that at constant temperature, sufficiently higher for pyrolysis; longer the duration of the experiment more will be the production of light cuts due to cracking of heavy components. These results provide key elements to extend the approach to a larger scale for field test application.