No abstract

No abstract

Property tests were first conducted to characterize the subject oil-inwater emulsions having three different interfacial tensions and three different droplet sizes in terms of their stability, droplet size distribution, and rheological behaviors. Then sandpack flow experiments were conducted, and permeability reduction tests were used to quantify the plugging performance of each of the different emulsions flowing at different flow rates through sandpacks. The results showed that the plugging effect of an oil-in-water emulsion was primarily due to the special flow behaviors of emulsion droplets in porous media; that is, the bulk viscosity of an emulsion contributed very little to the plugging effect. This paper has shown, for the first time, a correlation of emulsion plugging ability and interfacial tension. Permeability reduction of oil-in-water emulsions in sandpacks increased with an increase in interfacial tension and droplet size. At a fixed flow rate, emulsions with σ = 5.2 mN/m and σ = 9.3 mN/m had a more than 90% permeability reduction compared to the 66% reduction for the σ = 0.15 mN/m emulsion, and the injection pressure drop for emulsion with the largest droplet size was more than three times greater than that with the smallest droplet size. That is because, when an emulsion droplet passed through the pore constriction, the capillary resistance force it experienced increased as the interfacial tension increased, and larger droplets were more likely to be trapped in the pore constrictions than smaller droplets, therefore causing greater restrictions to the flow. Flow experiments also showed that the permeability reduction of emulsions decreased with an increase of the flow rate. In addition, the size differences of emulsion droplets in the effluents and influents were also compared and analyzed.

This paper will cover both caprock integrity and reservoir deformation, drawing from our years of experience in working with the heavy oil/oilsands industry in Alberta, Canada. Theoretical principles are described, analytical derivations made and field examples given, all to help illustrate the fundamentals and summarize the learnings in proactive utilization of geomechanics to enhance the reservoir performance and proactive consideration of geomechanics to ensure the caprock integrity. Topics include dilation tendency and fracturing behaviour in the oilsands, major geomechanical work components for the caprock integrity analysis/design, mini-frac tests and nonlinear coupled thermo-hydro-mechanical processes.

Based on its deformation properties, Alberta oilsands reservoir material is classified as an interlocked sands. It possesses relatively high initial friction strength and exhibits a significant dilation tendency once it is shear-mobilized. How does such a medium behave under high injection pressures? Using analytical derivations and numerical simulations, this paper illustrates the evolving shear-induced failure and tensile-dominated fracturing behavior in the oilsands. It concludes that the fracturing process is a combination of shear dilation and tensile parting at micro scales. Laboratory and field data exist to support the theoretical observations. Finally, a discussion will be given about impact of such fracturing behavior on the reservoir engineering processes. It will shed light on proactive utilization of the dilation for the in-situ oilsands development.