THE POTENTIAL OF NCG ENHANCED SAGD APPLICATION IN US HEAVY OIL RESERVOIRS

US heavy oil reserves equal about 105 billion barrels of which 13 billion had already been produced by 2004. This sizeable target comprises a prime candidate for implementation of a gravity‑stable thermal recovery method such as SAGD which has been very successfully applied in Athabasca heavy oil reservoirs. Because 50% of US heavy oil reservoirs are thinner than 100ft SAGD application might be less effective in terms of sweep efficiency and overburden heat loss. This simulation study aims to investigate not only the viability of implementing SAGD in thinner reservoirs by using a proposed well configuration involving vertical injectors and horizontal producers, but also the effect of the addition of non‑condensable gases (NCG) to steam. The generation of steam requires large amounts of water and fuel and one way have to reduce the heat required and improve the thermal efficiency is NCG addition. In this study, the SAGD performance utilizing vertical injectors with horizontal producers, and steam with and without NCG has been evaluated for a prototype reservoir model using a commercial reservoir simulator. The study demonstrates that the addition of NCG to steam reduced the steam‑oil‑ratio significantly compared to "steam‑alone" cases, thus making the overall process more economically attractive. Adding NCG to steam resulted in maintaining a higher average reservoir pressure, and limited the heat loss to the overburden. It could also go towards reducing greenhouse gas emission. The oil recoveries in the cases with the proposed gravity‑stable thermal recovery process using vertical injectors instead of horizontal injectors were found to be comparable to conventional SAGD, so using a combination of vertical injectors and horizontal producers may be an attractive option for recovering heavy oil using a gravity‑stable thermal recovery process involving the addition of NCG to injected steam in thinner reservoirs.