An aqueous synthetic acid composition is provided for use in oil industry activities. The composition comprises: lysine and hydrogen chloride in a molar ratio ranging from 1:3 to 1:12.5, preferably from more than 1:5 to 1:8.5. The composition may further comprise a metal iodide or iodate and an alcohol or derivative thereof. The composition demonstrates advantageous properties for synthetic acids at temperatures above 90° C. The composition is useful in various oil and gas industry operations. Preferred embodiments of the composition provide substantial advantages in matrix acidizing by increasing the effectiveness of wormholing.