Reservoir Fluid Characterization of Tar Sand and Heavy Oil Reservoirs-Impact of Fluid Heterogeneity on Production Characteristics

Steve Larter¹, Ian Gates¹, Jennifer Adams¹, Barry Bennett¹, Haiping Huang¹, Tamer Koksalan¹, and Milovan Fustic^2
1 University of Calgary, Calgary, AB
² Albian Sands Energy Inc. and Univeristy of Calgary, Calgary, AB

Traditional heavy oil and tar sand exploration and production strategies rely heavily on characterising key reservoir heterogeneities and assessments of fluid saturations. While these are crucially important, heterogeneities in distributions of fluid properties are equally or sometimes even more important but are often ignored. Heavy oil and tar sands are formed by microbial degradation of conventional crude oils, in which constraints such as charge mixing, biodegradation rate and critical controls such as water and nutrient supply to the organisms responsible for oil biodegradation, ultimately constrain degradation rates and the final distribution of API gravity and viscosity in both large and small oilfields. Large-scale lateral and small-scale vertical variations in fluid properties resulting from biodegradation and charge mixing are common with up to orders of magnitude variation in viscosity being common on a reservoir thickness scale. We describe and illustrate the quantitative geological controls on fluid property variations in heavy oil reservoirs and show examples of how petroleum reservoir geochemistry linked to reactive reservoir simulation can aid in heavy oil production in terms of optimizing well locations in thermal recovery operations or allocating production to long horizontal wells in non-thermal recovery.