This paper highlights how numerical simulation can be used as a tool to optimize the start-up phase of a SAGD process. During start-up, the main objective is to create a uniform communication path between the two wells by first circulating steam in both the injector and the producer well and then imposing a differential pressure between them. The dynamics of this process leads to important temperature and pressure transients that should be carefully considered when developing a start-up strategy. Usually, this start-up strategy aims at minimizing the time in which the well pair can be converted to full SAGD operation without causing any adverse effects on the long-term process performance.
A fully coupled wellbore/reservoir thermal simulator was used to conduct a sensitivity analysis, in which the effects of steam circulation rate, tubing diameter, tubing insulation and bottom hole pressure were investigated. The effects of the pressure differential between the wells, and the timing of imposing such pressure differential, were also looked at. To better account for the interaction between the processes happening in the wellbore and in the reservoir, the discretized wellbore was placed inside a hybrid reservoir grid. Aiming at investigating the influence of vertical and horizontal permeability, reservoir pressure, initial oil/water saturation and fluid properties, the start-up strategy was examined for three different cases representing the main heavy oil production areas in Alberta, Canada: Athabasca, Cold Lake and Peace River.