Carbonate matrix acidizing

In carbonate formations, matrix acidizing is principally a damage bypass treatment. If a carbonate formation is undamaged, a matrix acidizing treatment probably cannot be expected to do more than double the production rate. Carbonate matrix acidizing is discussed in part III of this book. 

Carbonate matrix acidizing is, realistically, a method for bypassing damage. Stimulation response potential is much greater when damage is present that can be bypassed by flow channels (wormholes) created by formation dissolution by acid. 

The physics of carbonate matrix acidizing is also complex. The operative mechanism in matrix acidizing of carbonates is the creation of conductive... 

Surfactant-gelled acid systems (also known as viscoelastic acid systems) represent a more recent development. Such systems have found success in carbonate matrix acidizing applications in particular. Certain special surfactant formulations can be added to acid that is above a certain concentration (e.g., >15% HCl) at which the surfactant does not impart appreciable viscosity. However, as the acid is injected and reacts in the formation, the surfactant generates viscosity (as a function of dissolved chloride ion and pH), thereby retarding reaction and providing, potentially, in situ diversion. As acid spends further, viscosity breaks back to reduced level (in the ideal case). 

Treatment placement or diversion in carbonate matrix acidizing is more difficult than in sandstone acidizing. This is because of the high solubility of carbonate formations in acid and the formation of channels. This eliminates the use of particulate diverters, such as rock salt, benzoic acid, and oil-soluble resin. 

The tables in this appendix present successful, nonroutine carbonate matrix acidizing treatment procedures. The examples are derived from published procedures used by other operators throughout the world. 

APPENDIX B CONVENTIONAL CARBONATE MATRIX ACIDIZING PROCEDURES 227... 

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