Post sagd in-situ combustion hybrid recovery method for oil-sands reservoirs

Abstract

Current in-situ thermal recovery methods, Steam Assisted Gravity Drainage (SAGD) and In Situ Combustion (ISC), have limitations which restrict their application in the heavy oil reservoirs. There are also a variety of undesirable environmental challenges associated with these existing techniques. To address some of these issues, hybrid technologies that attempt to synergistically combine both types of thermal processes were recently proposed. Since reported numerical simulation studies were unreliable due to large uncertainties in the mode of combustion occurring and the combustion kinetics, laboratory experiments were performed to evaluate the feasibility of the idea. A two­dimensional physical model was designed and fabricated with type-316 stainless steel to simulate the process. Eight Steam Assisted Gravity Drainage, experiments were completed at a representative reservoir pressure to validate the integrity of equipments and to investigate the effect of initial gas saturation, and high initial water and oil saturations in the SAGD operation. It was concluded that higher initial water and gas saturation negatively affected the process and reduced the oil recovery factor. Heat loss from the physical model was significantly increased and the heat transfer mechanism within the matrix was changed from conduction into convection. Subsequently, four hybrid experiments were completed with different air injection strategies like air injection into the SAGD chamber, and Top-Down combustion. The results proved the feasibility of the idea to implement ISC in the mature SAGD chamber. Total oil recovery factor was increased by 10 percent when combustion was restricted to the previously formed SAGD chamber. It was concluded that combustion within the existing steam chamber would be a solution to maintain the pressure in the mature SAGD chamber and to prevent non-desirable steam migration in the SAGD pattern. Implementing ISC in the growing SAGD chamber raised oil recovery by 20 percent. It is predicted that there is a potential to raise oil recovery factor by 40 percent if the whole pattern is swept.