An aqueous synthetic acid composition is disclosed for use in oil industry activities, the composition comprising: lysine and hydrogen chloride in a molar ratio ranging from 1 to 1:12.5, preferably from more than 1:5 to 1:8.5. The composition can also further comprise a metal iodide or iodate; an alcohol or derivative thereof. The composition demonstrates advantageous properties over known 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 as compared to conventional mineral acids such as HCl.