ABSTRACT
A systematic investigation of some factors which affect the reactivity of HCI towards carbonate rock was undertaken to provide technical criteria for the design and implementation of acid fracturing operations. This paper reports on the influences of pressure, temperature, acid concentration, flow rate, and gravity on the reaction rate of hydrochloric acid with carbonate rock. The experiments were conducted using an annular flow reactor which proved to be superior to previously reported reaction rate measuring equipment as it can be operated easily over a wide range of experimental conditions. The present study revealed that the reaction rate is an increasing function of temperature up to 200°F, then becomes independent of temperature above that. It is also an increasing function of acid concentration up to 15% but it becomes a decreasing function if the acid concentration is larger than 15%. The reaction rate is a decreasing function of pressure even if the pressure is larger than 1000 psi. The reaction rate is fastest when the acid flows in the direction of the gravitational force. To provide realistic data, laboratory determinations of reaction rates at high temperatures should be conducted under system pressures of 3000 psi or more.
