On the physics of cyclic steam stimulation

Steam fracturing as done during cyclic steam stimulation is an effective thermal process for initiating recovery from viscous oil reservoirs such as oil sands reservoirs found in Alberta, Canada and Liaohe, China. A key component of these processes is the ability to inject high temperature steam into the formation to fracture it which in turn raises its permeability and mobilizes the oil by lowering its viscosity. The dynamics of steam fracturing are not fully resolved especially how steam fingers into the reservoir and how its state changes as heat losses occur from the injected steam. The results of this study reveal that steam condensate, pressurized by the steam vapour upstream, fractures the formation. The results also show that dilation of the reservoir during steam injection relieves the pressure which in turn lowers the steam injection pressure below that of the case where no dilation occurs.