A rotating disk instrument was used to measure acid reaction rates, reaction order, and activation energy of reservoir rock from a deep dolomitic gas reservoir in Saudi Arabia. These values are required to optimize acidizing simulations. Results of more than 50 experiments are reported in this paper. Measurements were made from room temperature to 85degrees C at rotational speeds of 100 to 1,000 r/min and acid concentrations of 0.05 to 5 M HCl (0.2 to 17 wt%). The results show how acid dissolution rates change as the reservoir rock varied from 3 to 100 wt% dolomite. Factors affecting the measured parameters are discussed in detail. It was found that the reactivity of the rock varied from values expected for pure calcite marble to those expected for pure dolomite marble. At grain densities near 2.72 kg/dm(3) (expected for pure calcite), rock dissolution rates varied by more than an order of magnitude. due to rock mineralogy. At grain densities near 2.83 kg/dm(3) (expected for pure dolomite), rock dissolution rates were higher than that observed with pure dolomitic marble. Reaction rates depended on mineralogy and the presence of trace components such as clays.