Filter cake from drilling fluid and formation solids reduced production capacity of carbonate reservoirs in Saudi Arabia. On the basis of rock-mechanics studies of wellbore stability after drilling, it was suspected that normal HCl matrix stimulation would result in surface washout and wellbore enlargement. Emulsified acids have been shown to induce deep wormholes in carbonates that serve the same function as perforations to bypass drilling damage yet maintain formation integrity. The full-length paper details a new laboratory core-test procedure and provides a novel interpretation of scaleup equations developed for the study.