Ramified wormholes

In the petroleum industry, HC1 is routinely injected into carbonate formations in order to improve oil or gas production. It is known that the porous medium is not etched uniformly by the reactive fluid but that unstable dissolution patterns consisting of highly ramified, empty channels are formed. The channels are commonly called wormholes. As soon as a wormhole pattern develops, all the fluid will flow through it. Any local increase in the flow rate results in an increase in the local dissolution rate. A piece of porous medium in which a wormhole pattern has been created can be considered as composed of two parts the first part (wormholes) of very large permeability, and the second part keeping its original permeability. 

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