Steam Assisted Gravity Drainage (SAGD) is a successful method for recovering bitumen and heavy oil that is widely used in Alberta, Canada. However as the SAGD chamber fully develops (mature chamber), the oil production rate starts to decline and the steam oil ratio (SOR) to increase, directly affecting the economic viability of the process at this stage. Air injection after SAGD is one potential option to recover residual oil inside mature SAGD chambers, and to avoid having steam migration form adjacent SAGD patterns.
In this paper, a detailed laboratory experiment is presented in order to analyze the feasibility of in-situ combustion after an SAGD process. A 3D laboratory model was designed and constructed. The combustion cell was fitted with 48 thermocouples. A horizontal pair well is placed at the bottom of the model with interwell spacing of 3 cm. The SAGD chamber occupies 26% of the model. The first 15 cm of the injection well is preheated using an electric igniter. Enriched air is used for establishing the combustion chamber. After ignition, the combustion front develops near the injection side and progresses forward while laterally limited inside SAGD chamber boundaries. Flue gases and hot oil are produced through the bottom horizontal well. A maximum temperature of 617°C was recorded, with cumulative oil recovery of 12% original oil in place (OOIP). Post experiment analysis of the sand pack shows that, besides sweeping the residual oil in the SAGD chamber, the combustion process created a hard coke shell around the chamber, which isolated the steam chamber from the surrounding media.