High-quality emulsion of carbon dioxide (CO2) in aqueous alcohol-based gel (CO2 emulsion) was introduced into the Western Canadian Sedimentary Basin (WCSB) as a fracturing fluid in 1981. Since that time, the use of the fluid has been very successful, particularly in low-pressure, tight gas applications. The fluid has all the advantages of conventional high-quality CO2 foams/emulsions, with the added advantage of minimizing the amount of water introduced into the well.
The present paper will discuss a fluid that is an emulsion of liquid carbon dioxide in a base fluid of aqueous methanol. The discussion will include chemistry, rheological evaluations, and successful field utilization of these fluids in the Western Canadian Sedimentary Basin over the last decade.