A treatment with a stimulation fluid containing a reactive acid, used primarily to remove drilling damage and increase permeability near the well-bore.
In sandstone formations, the acid reacts with the soluble materials, such as drilling mud, formation matrix and enlarges the pore spaces. Effectively this is a cleaning process, attempting to return porosity and permeability to its original state.
In carbonate formations, the acid dissolves the entire formation matrix. The destruction of the matrix forms wormholes (highly conductive paths), which improve the formation permeability and enables enhanced production.
Matrix acidizing operations are performed at low rates and treatment pressures below the frac pressure of the formation. This enables the acid to penetrate the formation and increase the depth of treatment while avoiding damage to the reservoir formation.