Locking ring system for use in fracking operations

1. A sliding valve for opening one or more fluid ports in a piping string, comprising:

a valve body having a longitudinal bore, the valve body comprising said one or more fluid ports on an uphole portion of a sidewall thereof; and

a sliding sleeve slidably received in the longitudinal bore of the valve body and movable between an uphole closed position closing the one or more fluid ports and a downhole open position opening the one or more fluid ports;

wherein the sliding sleeve comprises:

a longitudinal bore;

a sleeve-profile on an inner surface of the sliding sleeve for mating a unique locking profile of a collet member when the collet member is received in the longitudinal bore of the sliding sleeve; and

a separate stop ring, received in the sliding sleeve, the stop ring having on an uphole side edge thereof a stop shoulder adapted to abut a portion of the unique locking profile of the collet member for preventing downhole motion of the collet member relative to the sliding sleeve, when and only when the collet member is received in the longitudinal bore of the sliding sleeve and said unique locking profile thereon mates said sleeve-profile;

wherein at least said stop shoulder of said stop ring is hardened to a hardness greater than the hardness of said sleeve profile or comprises a material having a hardness greater than the hardness of the sleeve profile.

2. The sliding valve as claimed in claim 1 , wherein at least said stop shoulder of said stop ring is comprised of a material selected from the group of materials comprising tungsten carbide, cobalt-chromium alloys, and nitrided steels, or a combination thereof.

3. The sliding valve as claimed in claim 1 , wherein said sleeve profile on said sliding sleeve is uphole to the stop ring.

4. The sliding valve as claimed in claim 1 , wherein the stop shoulder forms an acute angle with respect to a longitudinal axis of the sliding valve such that an inner edge of said stop shoulder is situated more uphole than an outer edge of said stop shoulder.

5. The sliding valve as claimed in claim 1 , wherein

the sliding sleeve, downhole of said stop ring, further comprises a coupling portion; and

said slidable sleeve further comprises a protection sleeve, an uphole end of said protection sleeve coupled to said coupling portion, said protection sleeve extending downhole; and

wherein the stop ring is an annular member; and

wherein the sliding sleeve further comprises a stop-ring seat for sandwiching the stop ring between the stop-ring seat and an uphole end of the protection sleeve.

6. The sliding valve as claimed in claim 5 , wherein the protection sleeve forms an annulus between a portion of an outer periphery thereof and said valve body when the sliding sleeve is at the closed position; and

wherein the protection sleeve isolates the annulus from the longitudinal bore of the valve body.

7. A sliding valve for opening one or more fluid ports in a production string, comprising:

a valve body having a longitudinal bore, the valve body comprising one or more fluid ports on an uphole portion of a sidewall thereof;

a sliding sleeve having a longitudinal bore and a sleeve-profile on an inner surface thereof, the sliding sleeve slidably received in the longitudinal bore of the valve body and movable between an uphole closed position closing the one or more fluid ports and a downhole open position opening the one or more fluid ports; and

a collet member, receivable in the longitudinal bore of the sliding sleeve, having a unique locking profile, said unique locking profile matingly engageable with said sleeve-profile;

wherein the sliding sleeve further comprises:

a separate stop ring, received therein, the stop ring forming a first stop shoulder for preventing downhole motion of the collet member relative to the sliding sleeve, when and only when the collet member is received in the longitudinal bore of the sliding sleeve and said unique locking profile of said collet member mates said sleeve-profile of said sleeve member;

wherein at least said first stop shoulder of said stop ring is hardened to a hardness greater than the hardness of said sleeve profile or comprises a material having a hardness greater than the hardness of the said sleeve profile.

8. The sliding valve as claimed in claim 7 , wherein at least said stop shoulder of said stop ring is hardened to a hardness equal to that of a downhole portion of the unique locking profile of said collet member.

9. The sliding valve as claimed in claim 7 , wherein the stop shoulder of the stop ring is comprised of a material having a hardness approximately equal to that of a downhole portion of the unique locking profile of said collet member.

10. The sliding valve as claimed in claim 7 , wherein at least said stop shoulder of said stop ring is comprised of a material selected from the group of materials comprising tungsten carbide, cobalt-chromium alloys, and nitrided steels, or a combination thereof.

11. The sliding valve as claimed in claim 7 , wherein said sleeve-profile on said sliding sleeve is uphole to the stop ring.

12. The sliding valve as claimed in claim 7 , wherein the stop shoulder forms an acute angle with respect to a longitudinal axis of the sliding valve such that an inner edge of said stop shoulder is situated more uphole than an outer edge of said stop shoulder.

13. The sliding valve as claimed in claim 7 , wherein

the sliding sleeve, downhole of said stop ring, further comprises a coupling portion; and

said slidable sleeve further comprises a protection sleeve, an uphole end of said protection sleeve coupled to said coupling portion, said protection sleeve extending downhole; and

wherein the stop ring is an annular member; and

wherein the sliding sleeve further comprises a stop-ring seat for sandwiching the stop ring between the stop-ring seat and an uphole end of the protection sleeve.

14. The sliding valve as claimed in claim 13 , wherein the protection sleeve forms an annulus between a portion of an outer periphery thereof and said valve body when the sliding sleeve is at the closed position; and

wherein the protection sleeve isolates the annulus from the longitudinal bore of the valve body.

15. The sliding valve as claimed in claim 14 , wherein said unique locking profile of the collet member comprises a stop shoulder at a downhole end thereof, for engaging the stop shoulder of the stop ring.

16. The sliding valve as claimed in claim 13 , wherein said unique locking profile of the collet member comprises a stop shoulder at a downhole end thereof, for engaging the stop shoulder of the stop ring.

17. The sliding valve as claimed in claim 7 , wherein said unique locking profile of the collet member comprises a stop shoulder at a downhole end thereof, for engaging the stop shoulder of the stop ring.

18. The sliding valve as claimed in claim 17 , wherein the stop shoulder on said collet member forms an acute angle with respect to the longitudinal axis of the sliding valve such that an inner edge of said stop shoulder on said collet member is situated more uphole than an outer edge of said stop shoulder on said collet member.

19. The sliding valve as claimed in claim 7 , wherein the unique locking profile of said collet member is a radially flexible collet-profile adapted to matingly engage said sleeve-profile on said sliding sleeve.

20. The sliding valve as claimed in claim 7 , wherein the collet member further comprises a cylindrical uphole portion, a cylindrical downhole portion, and a plurality of flexible splines therebetween coupled to the uphole and downhole portions, said flexible splines having thereon said unique locking profile.