A series of surfactants were evaluated in this study and the results were compared with conventional foaming agents used in fracture fluids. These surfactants were examined by surface tension measurements, bench-top foam height and half-life experiments, and viscosity measurements on a circulating foam rheometer. The foam rheometer allowed viscosities to be measured under conditions that are representative of those found in formations. Both nitrogen (N2) and carbon dioxide (CO2) foams were investigated. This paper presents detailed results obtained from laboratory experiments, which led to the identification of foamer A that exhibited excellent performance in the presence of nitrogen and carbon dioxide over a wide range of temperatures. Foamer A was found to be superior compared with conventional foamers, particularly at high temperatures. It is compatible with linear gels as well as crosslinked fluids commonly employed for fracturing treatments. Numerous fracturing treatments with foamer A have been successfully executed in the field.

It is emphasized in the paper that the type of foamer used in fracturing treatments has a great impact on the resulting foam stability and viscosity. In addition, bench-top foam height and half-life experiments can give an indication of the performance of a specific surfactant, but its behavior under downhole conditions cannot necessarily be inferred accordingly.

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