Steam Assisted Gravity Drainage (SAGD) has emerged as a promising in-situ oil recovery method from Athabasca oil sand deposits in Alberta, Canada. Despite numerous successes, optimal SAGD operations remain a major challenge. Present day operations depend on CAPEX intensive instrumentation to provide only a few critical process parameters, mathematical modelling for a priori or a posteriori "what if" scenarios and operator experience. In this paper, we present capabilities of Virtuoso, a first-of-its-kind comprehensive SAGD process simulator.
This simulator is capable of conducting end-to-end SAGD process simulation including SAGD reservoir, production and injection well bore pipeline management, and artificial lift methods. These types of simulations require simultaneous simulations of the multiphase hydraulic and thermal behavior of steam/water, oil/water, and oil/water/gas. This requires modelling multiple fluids types in porous media, in near well bore as it enters the tubing, in the perforated tubing, and in the annular space.
Previous efforts in the SAGD area have involved reservoir behaviour aimed at the full field over its five-year life. The comprehensive model described here is directed at the one hour to 30-day behaviour of the well. For example, an operator changes the set point for input steam rate, the ESP speed, and the annulus back pressure that may start to affect the production rate and lead to short circuiting of steam in 6 to 12 hours.
Because of the model's complete scope, the operator can proactively control the well operations and gain operational experience in a virtual simulator. The results from the model were validated with 200 days of field SAGD well operations data. An excellent agreement between the predictions and field data were obtained for emulsion flow rates, water cut, and reservoir sub-cool. Further, the capabilities of the simulator are presented through case studies such as steam shutdown/restarts, steam hot-spots. Artificial lift is demonstrated as a part of the field comparison study.