Propagation and control of fire front in the combustion assisted gravity drainage using horizontal wells

The propagating characteristics of combustion fronts and coke zones in the combustion assisted gravity drainage process were studied using 3D physical simulation experiments. The main mechanisms and factors affecting stable propagation of the combustion fronts were discussed. The experimental results show that the propagation of combustion front can be divided into startup stage, radial expands stage and moving forward stage. The top oil layer is ignited first at the startup stage. Ignition temperature, ignition time and air injection rate are the key parameters for successful ignition. At the radial expanding stage the combustion front grows in size and expands radically and downwards like a funnel, and the air injection rate should match the area of combustion front. After the combustion front propagates beyond the “toe” position, the burning zone would advance along the horizontal well at a certain angle. The controlled gas override and gas seal of the coke in the horizontal well contributes significantly to the overall stability of the process. In field pilot testing, well pattern, ignition parameters and regime of injection and production should be optimized to ensure the stable propagation of the combustion front.