Foam-based Fracturing Fluids

Foam fluids can be used in many fracturing jobs, especially when environmental sensitivity is a concern [1669]. Foam-fluid formulations are reusable, are shear stable, and form stable foams over a wide temperature range. They exhibit high viscosities even at relatively high temperatures [209]. 

In addition to the normal additives, foam-fluid formulations contain surfactants, nitrogen, and carbon dioxide as essential components. Cocobetaine and a-olefin sulfonate have been proposed as foamers [1386]. 

The content of the gas is called quality therefore a 70 quality contains 70% gas. Recently, foams with 95% gas have been examined. For such foam types, only foam prepared from 2% of an anionic surfactant with plain water had uniform, fine-bubble structure [782]. 

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Many shale gas service companies use groundwater pumped directly from the formation or treated water for their fracturing jobs. In some well stimulations, proppants are not needed to prop fractures open, so simple water or slightly thickened water can be a cost-effective substitute for an expensive polymer of foam-based fracturing fluid with proppant (Ely, 1994). Hydraulic fracturing performance is not exceptional with plain water, but, in some cases, the production rates achieved are adequate. Plain water has a lower viscosity than gelled water, which reduces proppant transport capacity. 

Fracturing fluids are often classified into water-based fluids, oil-based fluids, alcohol-based fluids, emulsion fluids, and foam-based fluids. 

There are also several types of fracturing fluid emulsions (including water- and oil-based emulsions) [47,48] and foams (including water-, oil- and alcohol-based... 

Gel breaking performance was an important indicator of its quality. The lower surface tension, the faster fracturing fluid s flowback. Base fluid viscosity was not more than 5 mPa-s after defoaming, and the surface tension of the base fluid was 17.27 mN/m, the interfacial tension was 0.34 mN/m. Foam fluid system was consisted of soluble surfactant molecules, so there was no residue after fracturing fluid gel breaking. 

Some fracturing fluids may include nitrogen and carbon dioxide to help foaming. Oil-based fluids find use in hydrocarbon-bearing formations susceptible to water damage, but they are expensive and difficult to use. Acid-based fluids use hydrochloric acid to dissolve the mineral matrix of carbonate formations (limestone and dolomite) and thus improve porosity the reaction produces inert calcium chloride salt and carbon dioxide gas. 

The majority of hydraulic fracturing treatments are performed using water-based fluids foams (with nitrogen or carbon dioxide as the gas phase) have been used extensively in recent years to reduce formation damage. Oil-external emulsions have also been used for... 

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