Colloid and Surface Chemical Problems in Non-Conventional Heavy Oil Recovery

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Abstract
Although emulsions have always been a problem for the petroleum industry, the producing of heavy crude oil can be further complicated by the presence of colloidal clays and asphaltenes which create a new type of emulsion. This phenomenon became apparent recently in the " Hot Water Process" for extracting bitumen from the Athabasca Tar Sands. The clays form membranous skins at the oil water interface which do not respond to conventional emulsion- breaking procedures. Caustic pH ranges, polyphosphates and other dispersing agents, rather than cationic flocculating, should be used to overcome this problem. Asphaltenes are colloidal crude oil constituents which also have the ability to form skins at the oil-water interface. These skins stabilize water in oil emulsions which do respond to conventional emulsion-breaking procedures. The asphaltenes contain very strongly polar chemical compounds, thus emulsion treating requires relatively high concentrations of expensive chemicals. A pH adjustment can reduce these requirements. Our Alberta heavy oils contain approximately 20 per cent asphaltenes, which, therefore, constitute a potential problem. The resinous acids in our heavy oils form another group of surface-active compounds. They stabilize water in oil emulsions, which can be broken more easily by conventional means. One other aspect of the resinous acids is their ability to form water-soluble soaps in the presence of caustic. Theoretically, these soaps could promote improved oil recovery. However, most of our heavy oil reservoirs contain clays which adsorb caustic and prevent this soap formation. The benefits observed due to caustic injection are believed to be due to the dispersion of the clays rather than the formation of soaps.

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