Methods, systems, and apparatus, including computer programs encoded on computer storage media, for fluid blob tracking. One of the methods includes identifying, by a computer system, a connected fluid phase region in a flow simulation. The method includes tracking, by the computer system, the connected fluid phase region over a first timeframe and a second timeframe. The method also includes determining, by the computer system, movement of the connected fluid phase region from the first timeframe to the second timeframe based on the tracking.