SAGD Circulation Phase: Thermal Efficiency Evaluation of Five Wellbore Completion Designs in Lloydminster Reservoir

The main objective during the circulation phase (start-up) of Steam Assisted Gravity Drainage (SAGD) is to lower the heavy oil or bitumen viscosity, to create inter-well fluid communication between the injector and producer well and to uniformly warm-up the lateral section of the well pair to achieve uniform steam chamber growth during the life of the SAGD well pair. Typically, the circulation phase (start-up) lasts between three and six months and it is completed when the temperature between the producer and injector is high enough, generally greater than 80°C. It has been proven that during the circulation phase (start-up) of a SAGD well pair, the variations in thermal efficiency result from factors such as tubing size, well trajectory, well length, completion configuration, reservoir properties, and operating parameters. There is not any published study performed in the Lindbergh area in Alberta, Canada that determines the thermal efficiency of different completion designs during the circulation phase (start-up) of a SAGD well pair in a Lloydminster formation. Therefore, in a previous study, a discretized thermal reservoir/wellbore modelling simulator (Exotherm, 2016) was used to history-match field data obtained from a SAGD well pair in the Lloydminster area, and, subsequently, this paper uses the simulation model to evaluate and compare the thermal efficiency of five different completion design cases during the SAGD circulation phase (start-up) in the Lloydminster formation. These completion designs include: bare tubing in a dual string, vacuum insulated tubing (VIT) in a dual string and single string, and gas blanket (methane) in a concentric string. The results show that completion design configuration impacts the heat transfer and thermal efficiency of the circulation process.