Locking ring system for use in fracking operations

1. 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 said one or more fluid ports on an uphole portion of the sidewall thereof; and

a sliding sleeve 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 sleeve body having a longitudinal bore;

a sleeve-profile on an inner surface of the sliding sleeve for mating with a unique locking profile of a collet member when the collet member is received in the longitudinal bore of the sliding sleeve, to allow the collet member to actuate the sliding sleeve and move said sliding sleeve from the uphole closed position to the downhole open position to open the one or more fluid ports;

a separate stop ring received in the sliding sleeve, said stop ring comprising a cylindrical inner surface and a stop shoulder on an uphole side thereof, said stop shoulder engageable with the collet member for preventing the collet member in the longitudinal bore of the sliding sleeve from moving downhole; and

a protection sleeve downhole to the sleeve body; and

wherein the stop shoulder has a first 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;

wherein at least a coupling portion of the protection sleeve is received in the sleeve body for coupling the protection sleeve to the sleeve body;

wherein at least when the sliding sleeve is at the closed position, the protection sleeve and the valve body form an annulus therebetween; and

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

2. The sliding valve as claimed in claim 1 , wherein the sleeve body comprises a stop-ring seat for sandwiching the stop ring between the stop-ring seat and an uphole end of the protection sleeve.

3. The sliding valve as claimed in any one of claims 1 , or 2 , wherein at least said stop shoulder is hardened to a hardness greater than that of the material of the sliding sleeve or comprises a material having of a hardness greater than the hardness of the sliding sleeve.

4. The sliding valve as claimed in claim 2 , wherein said stop ring is comprised of a material having a hardness greater than that of the material of the sliding sleeve.

5. The sliding valve as claimed in any one of claim 1 , or 2 wherein at least said stop shoulder is hardened to a hardness equal to that of the unique locking profile of the collet member.

6. The sliding valve as claimed in any one of claim 1 , 2 wherein the stop shoulder is comprised of a material having a hardness approximately equal to that of the downhole portion of the unique locking profile of the collet member.

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 said one or more fluid ports on an uphole portion thereof and a ratchet structure on an inner surface of a downhole portion thereof; and

a sliding sleeve 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 sleeve body having a longitudinal bore, the sleeve body comprising a ratchet structure on an outer surface of a downhole portion thereof, the ratchet structure of the sleeve body engageable with the ratchet structure of the valve body for locking the sliding sleeve when the sliding sleeve is at the downhole open position; and

a protection sleeve downhole to the sleeve body, at least a coupling portion of the protection sleeve received by the sleeve body for coupling the protection sleeve to the sleeve body;

wherein at least when the sliding sleeve is at the closed position, the protection sleeve and the valve body form an annulus therebetween; and

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

8. The sliding valve as claimed in claim 7 , wherein at least when the sliding sleeve is at the closed position, the ratchet structure of the sleeve body and the ratchet structure of the valve body are in the annulus.

9. The sliding valve as claimed in claim 7 , wherein the sliding sleeve further comprises a stop shoulder for preventing a collet in the longitudinal bore of the sliding sleeve from moving downhole.

10. The sliding valve as claimed in claim 9 , wherein the stop shoulder has a first 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.

11. The sliding valve as claimed in claim 9 , wherein the stop shoulder is formed by a stop ring received in the sliding sleeve.

12. The sliding valve as claimed in claim 11 , wherein the sleeve body comprises a stop-ring seat for sandwiching the stop ring between the stop-ring seat and an uphole end of the protection sleeve.

13. The sliding valve as claimed in claim 9 , wherein at least said stop shoulder is hardened to a hardness greater than that of the material of the sliding sleeve or comprises a material having of a hardness greater than the hardness of sliding sleeve.

14. The sliding valve as claimed in claim 11 , wherein said stop ring is comprised of a material having a hardness greater than that of the material of the sliding sleeve.

15. The sliding valve as claimed in claim 9 , wherein at least said stop shoulder is hardened to a hardness equal to that of a unique locking profile of the collet.

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