Hydrochloric acid is commonly used in the upstream sector of the oil and gas industry to enhance production from carbonate reservoirs.. Unlike calcite (calcium carbonate), the rate of reaction between dolomite and hydrochloric acid is much slower. Thus, in fracture acidizing operations, this slow reaction rate hinders the efficiency of dissolution which is required to create etching pattern on the fracture surface. Accordingly, use of an acid fluid that can accelerate the reaction with dolomite-rich formation at reservoir conditions can be beneficial to exploit the result of the stimulation treatment.<br/>Boosting the rate of reaction between dolomite and 28 wt.% hydrochloric acid (HCl) was achieved in this study through an additive-driven chemical approach using sulfonate-based surfactants. Several surfactants were selected for their potential to serve as reaction accelerators by conducting high throughput static dissolution tests using outcrop dolomite core samples. The efficiency of the additive was evaluated through the calculation of the weight loss of the rock sample after the reaction. To evaluate the performance under reservoir conditions, a reaction kinetics study was performed using a rotating disk apparatus at a pressure of 3000 psi, across a temperature range from up to 300 °F. It was found that selected additives combined with 28 wt.% HCl increased the rate of dissolution of dolomite. The kinetics data collected at 200 and 300 °F showed that the reaction rate of dolomite and one of the developed formulations can be improved by 30 to 50%. The developed fit-for-purpose acid formulation opens the door for improving the stimulation efficiency in dolomite-rich formations.

New acid formulation to boost reaction with dolomite rocks

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