Wormholes are long, finger-like channels that form due to the flow and dissolution heterogeneity in the soluble porous rock matrix. Wormholes are major flow pathways, which significantly increase the permeability of the rock formation. A fundamental understanding of the wormhole formation is crucial in civil, environmental and energy engineering research and practice. A series of gypsum core flood tests were conducted to study the effect of flow rate on the dissolution of the gypsum rock matrix and the formation of wormholes. High-resolution X-Ray computed tomography (CT) was used to determine the geometry of the wormholes resulting from different flow rates. Skeleton analysis and fractal analysis were used to study the geometry of the wormholes resulting from different flow rates using skeleton analysis and fractal analysis. These analyses showed that higher flow rates resulted in more complex wormholes regarding the total wormhole length and fractal dimensions.