The operational production period in Toe-to-Heel Air Injection (THAI) has been investigated via numerical simulation of a field scale section of the Conklin THAI pilot in the Athabasca Oil Sands. THAI is an advanced horizontal well development of the in situ combustion process for heavy oil recovery. It operates as a ‘short-distance’ displacement process, and is being applied to bitumen and heavy oil reservoirs.
Breakthrough of oxygen into the production well is predicted to occur after 10.8 years of oil production. This occurs during the declining oil rate period, which follows a sustained period of constant rate production. Prior to oil rate decline, the oil recovery factor was 63 %. High combustion temperatures aid continued expansion of the steam bank, maximizing oil recovery. Economic and also safety factors determine the ultimate decision point, concerning termination of operations. On the one hand, maximum oil recovery is determined by longer operation time, but this is also influenced by safety considerations, principally, the approach to oxygen breakthrough. Terminating the process early maximises the financial rate of return, but at the expense of total oil recovery. Reduction in the oil price is probably the most significant factor affecting profitability, but this also depends on timing and degree of financial risk.