Investigation of Unresolved Interface "Rag Layer" in Athabasca Oil Sand Bitumen In Situ Recovery

Area of Science:

• Petroleum Engineering
• Chemical Engineering
• Materials Science

Background:

• Steam-assisted gravity drainage (SAGD) is a primary in situ bitumen recovery method.
• SAGD processes produce a mixture of water, hydrocarbons, and sand requiring separation.
• Disruptions in separation, like rag layer formation, can impact process efficiency.

Purpose of the Study:

• To investigate the occurrence and morphology of rag layers in SAGD treaters.
• To quantify factors influencing rag layer formation and volume.
• To understand the role of solids and emulsions in rag layer development.

Main Methods:

• Laboratory-scale experiments simulating SAGD conditions.
• Analysis of field test data from SAGD operations.
• Microscopic imaging to characterize rag layer morphology and emulsion types.
• Quantification of solids, mixing speed, and solvent effects.

Main Results:

• Rag layer formation and volume are influenced by solids, mixing speed, and solvent addition.
• Microscopic analysis revealed both water-in-oil and oil-in-water emulsions within the rag layer.
• Hydrophobic fine inorganic solids (<10 μm) accumulate at the oil-water interface, contributing to rag layer formation.
• Rag layer boundaries correlate with droplet agglomeration, increasing near the oil-water interface.

Conclusions:

• Fine inorganic solids play a crucial role in stabilizing rag layers in SAGD treaters.
• Fluctuations in feed solids content can explain the seemingly random occurrence of rag layers in field operations.
• Understanding rag layer formation is key to optimizing separation processes in SAGD.