Effects of cationic and anionic surfactants on the stability, rheology and proppant suspension of nanoparticle-stabilized fracturing foams at elevated temperature

Much attention has been paid to applying liquid foams in hydraulic fracturing in the past few years due to their significant benefits, including minimal formation damage. In the current literature, the combination of anionic surfactants and nanoparticles (NP) has been thoroughly studied to improve foam-based fracturing fluids' thermal stability and viscosity. However, very little research has focused on the synergy between cationic surfactants and NP, which results in a limited understanding of the effects of this mixture on enhancing the properties of fracturing foams, especially at reservoir temperature. This paper investigates and compares the synergy between cationic/anionic surfactant and silica nanoparticles (SNP) in improving the fracturing foams' stability, rheology and proppant-carrying capacity under ambient and elevated temperature conditions. The experiments involved foamability, bulk static stability, viscosity measurement and proppant settling tests at fixed NP concentration and varied surfactant concentrations. The results showed that the foams' properties were gradually enhanced with increasing surfactant concentration until reaching a peak at around 0.05-0.1 wt%. At ambient and elevated temperatures, the foams stabilized by SNP and cationic hexadecyltrimethylammonium bromide (CTAB) surfactant had higher half-life, apparent viscosity, and better proppant-carrying ability than those stabilized by SNP and anionic sodium dodecyl benzene sulfonate (SDBS) surfactant. The properties of CTAB/SNP foams were found most outstanding at medium CTAB concentration; however, they declined dramatically at very low or very high surfactant concentration. This study enhances our understanding of the influences of surfactant type and concentration on the stability, rheology and proppant suspension behaviour of nanoparticle-stabilized foams, which directly contributes to developing an effective foam system for high-temperature fracturing application.