Gas flotation is often used during treatment of the oilfield produced water. It relies on the generation of gas bubbles and their attachment to oil drops, for example, by forming an oil film on the surface of a gas bubble. In this paper, we present a microfluidic technique for investigating the attachment of crude oil drops to gas bubbles through the spreading mechanism. The developed method allowed us to systematically study the effect of the oil, water, and gas phases, where the investigated parameter was the amount of oil droplets attached to gas bubbles through spreading. The highest attachment efficiency was observed at low or neutral pH. By reducing the salinity, the electrostatic repulsion increased, which had a negative effect on the attachment. The presence of dissolved components stabilized the oil drops and gas bubbles, which decreased their attachment through spreading. Replacing nitrogen with methane improved the attractive interactions between bubbles and oil droplets, enhancing the attachment of oil. The results confirm the potential of microfluidics in studying bubble-droplet interactions, relevant for industrial processes.