Highly Stabilized Foam by Adding Amphiphilic Janus Particles for Drilling a High-Temperature and High-Calcium Geothermal Well

Fabricating Janus particles that consist of two distinct functional regions is an intriguing research topic. In this study, wax colloidosomes were successfully prepared by the Pickering emulsion method. After hydrophilic modification with an amino-containing silane agent and separate hydrophobic modification with several silane coupling agents with different carbon chain lengths, a series of Janus particles that differed in their hydrophilic lipophilic balance were facilely fabricated. The results show that the (3-aminopropyl)triethoxysilane-SiO2-dodecyltrimethoxysilane (NH2-SiO2-12C) Janus particles possess the best foam stability. As a result of their suitable contact angle of 80°, high positive ζ-potential, and good surface activity, these foams display the characteristics of low surface tension, high dilational elasticity, nonspherical shapes, large sizes, and thick films, which together result in the extension of the drainage half-life of the foam from 448 to 778 s in comparison with the foam of pure foaming agent solutions. Moreover, compared with a foam with no stabilizer or those stabilized by a soluble foam stabilizer and homogeneous hydrophobic-modified silica particles, NH2-SiO2-12C-stabilized foam can extend the drainage half-life to 668 s after hot rolling for 16 h at 280 °C and resist a CaCl2 concentration of 0.8 wt %. Benefiting from their excellent thermal stability and salt tolerance, these Janus particles are expected to be promising candidates for use as foam stabilizers in high-temperature and high-calcium conditions, including drilling, enhanced oil recovery, "waterless" fracturing, and, especially, in geothermal wells.