This paper describes the results of a simulation and optimization study on the application of a solvent-additive steam-assisted gravity drainage (SAGD) process to reservoirs with associated basal water. A review of related studies is provided, together with a discussion of the pros and cons of potential alkane solvents in basal water reservoirs. Economics and the impact of dynamic and ultimate retention are discussed.

A general conclusion drawn from literature is that optimal solvent application to SAGD in reservoirs will likely involve time variations in both rate and composition of the solvent. This is also the case for reservoirs with associated basal water. This results in an optimization problem that has a large number of dimensions, and is very nonlinear. Genetic algorithms, which mimic biological evolution, have been found to be extremely effective in addressing such problems.

A key product of this effort, optimized for a simple clastic reservoir with associated basal water, is presented. The study produced an operable process, which could be described as a new combination of pre-existing concepts. The process offers material improvements in thermal bitumen supply costs, as well as recovery factor. Major reductions in the physical steam/oil ratio (SOR), (and therefore) capital intensity, water use and carbon emissions, are indicated.

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