High-pressure small-angle neutron-scattering measurements show that a dichain hydrocarbon-fluorocarbon surfactant ((C7H15)(C7F15)CHSO4-Na+) stabilizes spherical droplets, with mean water core radius around 25 Angstrom, in a water-in-CO2 microemulsion (temperature = 25 degrees C, pressure = 500 bar). At lower pressures droplet clustering is observed. Our structural work on this system builds on initial phase stability studies by Johnston et al.