Abstract Acid fracturing has been extensively used as a well proven method to stimulate carbonate formations in the Ghawar field. The unique reservoir characteristics found in all the wells producing from carbonate reservoirs in the field make acid fracturing stimulation operations highly dependent on fracture stimulation capability to connect multilayered zones, adequate fluid efficiency (effective leakoff control), fluid properties to generate proper fracture geometry with high-pressure/high temperature environments, and engineering work to design an economical but successful stimulation treatment. This paper discusses a case study for a gas well in a carbonate reservoir in Saudi Arabia where an effective diversion technique with associative polymers and new optimized acid formulations was successfully performed. The treatment included a delayed borate crosslinked fluid used as a pad to create and extend the hydraulic fracture, and two 26% hydrochloric (HCl) acid blends (one emulsified and the other gelled) to efficiently penetrate and etch the surface rock. Also, proper diversion stages were included to ensure full stimulation zonal coverage, and rigorous engineering efforts to ensure that an economical but successful acid fracturing stimulation treatment could be performed. Both the emulsified and gelled 26% HCl acid blends used were extensively tested for corrosion at a temperature of 275 °F. Additionally, emulsion stability tests were carried out on the mixtures to ensure retardation properties at bottom-hole conditions, and achieved a longer acid fractured etched length with optimum conductivity. Based on lab results, a new optimized emulsified acid formulation was finally designed and implemented. The paper also summarizes the main results obtained when the previous optimized acid stimulation system was carried out in a highly deviated well. The final gas production results exceeded expectations, thereby confirming the effectiviness of a special acid blend for stimulation of carbonate formations.