The successful matrix stimulation of carbonate reservoirs requires that live acid penetrate past the formation damage. Effective acid penetration is facilitated either by transport through natural fractures or the formation of dissolution channels (wormholes) during the acidizing process. The optimal formation of wormholes and/or transport of live acid along natural fractures depends on the rate of reaction between the acid and the formation minerals, the rate of acid transport to the mineral surface, and the rate of acid convection along the wormhole and/or fracture. There are three prevailing theories in the literature that estimate the efficacy of acid stimulation treatments in carbonate formations. These theories predict the conditions at which wormhole formation occurs most efficiently and are based on the existence of: 1) an optimum injection rate at a transition between reaction-rate limited and fluid-loss limited regimes, 2) an optimum Peclet number, and 3) an optimum Damköhler number.

The models are compared with a large set of experimental data representing a wide range of conditions encountered worldwide. The results show the conditions under which each theory is most appropriate. Parameters studied include injection rate, temperature, and fluid-mineral system. Validated models are then used to simulate skin evolution during actual matrix acidizing treatments. Results of the laboratory and field validations highlight gaps in the current technology and provide directions for further investigation.

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