Dominant wormholes

Dominant wormholes (primary channels with some branching)... 

Dominant wormhole. At higher injection rates and with retarded or slower-reacting acids, the stimulation fluid has the opportunity to further extend the tip of the channel being formed. This gives rise to a thinner,... 

Generally, a dominant wormhole represents the optimum combination of injection rate and reactivity. This wormhole pattern has the best chance of extending beyond the damage zone. It has sufficient conductivity and branching to provide significant production flow to the wormhole and into the wellbore. 

As noted in Sect. 10.1, heterogeneities play a dominant role in the migration of contaminants in the subsurface. Nonuniform, preferential patterns of flow and transport are ubiquitous. It is important to recognize that, at the field scale, contaminant movement generally is very difficult to anticipate. In natural soils and aquifer materials, macropores, soil cracks and aggregates, fissures, solution channels, root paths, and wormholes, as well as variable mineral composition (e.g., clay aggregates... 

The formation of smaller, more branched wormholes, which is promoted by retarding add, can be benefidal, at least to a certain degree. As explained in chapter 10, excessive branching is not desirable, because it will reduce live acid penetration and flow-path conductivity. Retarding acid to the extent appropriate will result in branching, but not at the expense of the formation of dominant, deeply penetrating wormholes. 

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