The majority of gas reservoirs in conventional fields exist in carbonate reservoirs, and the largest gas reservoir in the world is located in a carbonate formation. Actual rock samples from drilled gas wells showed that the anhydrite content could reach 50%; nevertheless, 10-20% anhydrite content is very common in carbonate reservoirs. The presence of anhydrite degrades the stimulation efficiency because of its low solubility in all stimulation fluids. In this work and for the first time, a new two-stage treatment was developed to stimulate carbonate reservoirs with high anhydrite content using actual reservoir rock samples. The treatment involves flushing the core with a combined solution of 10 wt % K2CO3 in KOH solution and then injecting HCl; HCl-based fluids; organic acids such as citric, acetic, and formic acid; or low-pH chelating agents, such as L-glutamic acid, N,N-diacetic acid. The preflush stage converts anhydrite (calcium sulfate) to calcite (calcium carbonate), which can then be dissolved easily using HCl or any low-pH acids. A computed tomography scan showed that the new method created branched wormholes compared to the conventional HCl treatment due to the anhydrite conversion. Inductively coupled plasma and ion chromatograpy analyses showed higher sulfate content in the case of coreflooding with the new formulation due to the anhydrite conversion. NMR showed that more pores were created when the carbonate core was stimulated using the new method compared to the conventional treatment using HCl. A fine-scale model was built to match the experimental outcomes in terms of wormhole shapes and pore volumes to breakthrough. Then, radial flow simulations, representing field matrix acidizing, were conducted to predict the efficiency of wormhole penetration using the new formulation. On the basis of our experimental and modeling analyses, the new method can be considered as an efficient way to enhance the stimulation process in gas reservoirs with high anhydrite content.