Effect of elastic properties on the propagation of gelled and in-situ gelled acids in carbonate cores

• Live gelled and live in-situ gelled acids had weak elastic properties.
• Only partially neutralized (pH 3.2) in-situ gelled acid had strong elastic properties.
• Polymer filter cake was observed only for the cores that were treated with gelled acid.
• In-situ gelled acid forms a thin layer of gel that minimizes the leakoff preventing the filter cake.
• The elastic properties enhanced the ability of the gel to remain around the wormhole plugging it.

Polymer-based acids exhibit some viscoelastic properties. Therefore, the objectives of this study are to determine the elastic and viscous properties of these acids, how these properties change as the acid reacts with carbonate formations, and their effect on the propagation of the acid inside 20-in. long carbonate cores.Live gelled and in-situ gelled acids had weak elastic properties, while partially neutralized (pH 3.2) in-situ gelled acid had strong elastic properties. Polymer filter cake was observed for the cores that were treated with gelled acid while the cores that were treated with in-situ gelled acids did not form this filter-cake. In-situ gelled acid formed a thin layer of gel that minimized leakoff, which prevented the formation of filter cake. For gelled acid, the polymer filter cake reduced the core permeability to zero. The wormhole obtained in the case of gelled acid was nearly linear and thinner than those created by in-situ gelled acid. The strong elastic properties enhanced the ability to get the gel to remain around the wormhole, which forced the next acid stage to change its direction.