A major constraint in developing shale reservoirs in many regions of world is the lack of a good water supply, and the development of fracturing fluids which use no or minimal amount of water can help remedy the problem. Low water-content (20-30%) CO2, N2 or air foams that are stabilized by fly ash nanoparticles and a low concentration surfactant not only generate a high apparent viscosity (up to 60 cp) to support high fracturing pressure but also have ability to carry proppant sand grains. Since fly ash is similar in composition (mainly of quartz) to silica, the knowledge earlier gained in generating silica nanoparticle-stabilized dry CO2 foams can be utilized to generate nano-milled fly ash-stabilized foams with CO2, N2 and air as internal phase. View-cell foam stability observations and capillary-viscometer apparent viscosity measurements were carried out for varying concentrations of nanoparticle and surfactant (specifically, lauryl amidopropyl betaine) to confirm that stable dry foams could be generated for a range of salinities (&lt; 10 wt% NaCl). The effect of fly ash particle size on foam stability was also investigated. Proppant-carrying tests were performed by placing sand grains of varying sizes on top of a stationary foam, and observing the gradual settling of sand grains with time. Fly ash-stabilized foams sustained the sand grains for 2-5 hours under high salinity conditions. Use of air as a low-cost substitute for CO2 or N2, with its risk for downhole ignition reduced as it is in foam state, offers an intriguing potential.

Fly ash nanoparticle-stabilized dry foams as fracturing fluids

2019 Spring National Meeting

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