wherein the cationic viscoelastic surfactant is in at least a sufficient critical concentration in the treatment fluid to impart viscoelastic behavior to the treatment fluid after at least some of the strong acid spends in the formation. 

2. ( canceled) 

3. The method according to claim 1, wherein the strong acid comprises hydrochloric acid. 

4. The method according to claim 1, wherein the cationic viscoelastic surfactant is or comprises a viscoelastic surfac› tant having a nitrogen atom with short chain alkyl groups. 

5. The method according to claim 1, wherein the cationic viscoelastic surfactant is or comprises a quaternary ammo› nium fatty amine. 

6. The method according to claim 5, wherein the quater› nary ammonium fatty amine is or comprises bis(hydroxyeth› yl)methyloleylammonium chloride. 

7. The method according to claim 5, wherein the design temperature of the zone is higher than 93° C. (200° F.). 

8. The method according to claim 1, wherein the design temperature of the zone is higher than 93° C. (200° F.). 

9. The method according to claim 1, wherein the non› cationic corrosion inhibitor is or comprises the anionic organic component. 

10. The method according to claim 1, wherein the non› cationic corrosion inhibitor is or comprises methyl ester sul› fonate. 

11. The method according to claim 9, wherein the treat› ment fluid additionally comprises: a corrosion inhibitor inten› sifier. 

12. The method according to claim 1, wherein the treat› ment fluid additionally comprises: a corrosion inhibitor inten› sifier. 

13. The method according to claim 12, wherein the corro› sion inhibitor intensifier is or comprises the anionic organic component. 

14. The method according to claim 12, wherein the corro› sion inhibitor intensifier is or comprises triphenylphosphine. 

15. The method according to claim 1, wherein the design temperature of the zone is up to 121 ° C. (250° F.). 

16. The method according to claim 1, further comprising the step of: flowing back fluid from the zone. 

17.-27. (canceled) 

* * * * * 

