Steam assisted gravity drainage performance: A study on the impact of non-condensable gases

Gases such as carbon dioxide, nitrogen and methane, which can be present in a SAGD steam chamber, but do not condense into the liquid phase to any large degree at reservoir conditions are referred to as non-condensable gases (NCG's). The co-injection of NCG's along with steam during the SAGD process results in changes pertaining to production rate, total oil production and the amount of steam required to mobilize the bitumen in place. This study is aimed at investigating the impact of NCG's on SAGD performance by means of numerical simulation. Fulfilling this objective necessitates establishing a solid understanding of gas solubility in both bitumen and water, which would then lead to generating well-substantiated K-values for the gas-bitumen and gas-water phase equilibria.;This study presents a novel approach that can be used to predict the K-values for both the gas-bitumen and gas-water phase equilibria at a wide range of pressures and temperatures. In addition, this study provides insights regarding the impacts of naturally occurring, as well as continuously and intermittently co-injected gas, at different stages ranging from the early times of the SAGD process to the "blowdown" phase. The simulation results of this study show that methane co-injection along with steam is generally not beneficial. Although it can reduce the heat loss to the overburden to some extent, the reduction in oil drainage rate and the final recovery factor negates the benefits of such heat loss reduction.