HIGH PRESSURE LOCK ASSEMBLY

Abstract

A lock assembly including a mandrel having at least one window therein. At least one dog corresponds to the at least one window and is radially extendable therethrough. The at least one dog is operatively arranged for engaging at least one feature of a tubular radially disposed with the mandrel. At least one seal element is arranged for sealing the mandrel with respect to the tubular and operatively positioned with respect to the at least one dog for maintaining the mandrel solely in compression against the at least one dog during fluid pressure loading on the mandrel in either longitudinal direction with respect to the lock assembly.

Description

BACKGROUND

Lock assemblies are ubiquitous in the downhole drilling and completions industry. One common type of lock assembly involves locking a plug, choke, pressure holding device, tool, etc. in place by radially extending a plurality of dogs into engagement with corresponding features of a radially disposed tubular. In order to accommodate the dogs, windows must be formed in a mandrel or other component of the tubular string, with relatively narrow struts located between each window presenting likely failure points when the string experiences high pressure situations. This results in the need to balance the width of the dogs and the width of the struts, as making either too small can result in failure of the system (e.g., inability of the dogs to lock the string in place and/or fracture of the struts due to heavy loading). In view of these issues and the prevalence of dog type locking systems in the industry, advances and alternatives in the field of lock assemblies are always well received.

BRIEF DESCRIPTION

A lock assembly including a mandrel having at least one window therein, at least one dog corresponding to the at least one window and radially extendable therethrough, wherein the at least one dog is operatively arranged for engaging at least one feature of a tubular radially disposed with the mandrel, and at least one seal element arranged for sealing the mandrel with respect to the tubular, the at least one seal operatively positioned with respect to the at least one dog for maintaining the mandrel solely in compression against the at least one dog during fluid pressure loading on the mandrel in either longitudinal direction.

A method of locking an assembly including engaging at least one dog of an assembly with a profile of a tubular radially disposed with the assembly, loading the assembly in either longitudinal direction by pressurizing a fluid, the assembly including at least one seal element for sealing the assembly with respect to the tubular, and maintaining the assembly solely in compression against the at least one dog regardless of the longitudinal direction of the loading.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a quarter-sectional view of a lock assembly being loaded in a first direction;

FIG. 2 is a quarter-sectional view of the lock assembly of FIG. 1 being loaded in a second direction opposite to the first direction; and

FIG. 3 is a quarter-sectional view of a lock assembly according to another embodiment described herein.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring now to FIG. 1, a lock assembly 10 is shown having a mandrel 12 radially disposed with a tubular 14. The mandrel 12 includes at least one first dog 16 and at least one second dog 18 axially displaced from each other. For simplicity, the dogs 16 and 18 may be referred to in plural although only one of each is needed in the assembly 10. The dogs 16 and 18 are, e.g., arranged in windows 20 of the mandrel, with struts 22 adjacent the windows 20 and connecting between opposite axial sides of the dogs 16 and 18. The struts 22 are shown in hidden lines because one strut is located behind each dog 16 and 18 (with multiple struts 22 alternatingly arranged with the windows 20 about the mandrel 12, with one of the dogs 16 and/or 18 in each window 20). Due to the reduced widths of struts and the stress concentrations that result from presence of windows, fracture of struts presents a likely mode of failure during high pressure loading of current dog-type lock assemblies. This problem is alleviated by the current invention as discussed in more detail below.

The dogs 16 and 18 are arranged to be extended from the mandrel 12 for engagement with corresponding recesses 24 and 26 in the tubular 14 in order to lock the assembly 10, and therefore the string of which it is a part, with respect to the tubular 14. The dogs 16 and 18 could be radially extendable according to any known arrangement. For example, in the embodiment of FIG. 1 the dogs 16 and 18 are arranged to climb ramps 28a and 28b located between relatively movable components 12a, 12b, and 12c of the mandrel 12, which could be, e.g., threaded together, with relative movement therebetween prevented until the dogs 16 and 18 are aligned with their respective recesses 24 and 26.

In FIG. 1, the assembly 10 is shown loaded in a direction indicated by an arrow 30. For example, the loading indicated by the arrow 30 could be the result of a hydraulic or some other fluid pressure event, e.g., acting against an up-hole side of the assembly 10. Accordingly, the assembly 10 includes a seal element 32 for sealing the mandrel 12 against the tubular 14, such that pressure on the mandrel 12 in the direction of the arrow 30 acts to move the assembly 12, forcing the dogs 16 to engage against a profile or face 24a of the recess 20, where the tubular 14 picks up the loading. In response to picking up the loading, the tubular 14 exerts a reaction force on the dogs 16, which is then exerted by the dogs 16 on the mandrel 12, as indicated by the direction of an arrow 34. The mandrel 12 is put into compression between the two forces indicated by the arrows 30 and 34. The dogs 18 are not in contact with either of a set of profiles 26a and 26b of the recess 26 when the dogs 16 are engaged against the profile 24a.

When loaded in the opposite direction as indicated by an arrow 36 in FIG. 2, e.g., the result of a pressure event acting against a downhole side of the assembly 10, the assembly 10 is shifted until the dogs 18 contact the profile 26a of the recess 26. In response to the tubular 14 picking up the loading at the profile 26a, the tubular exerts a reaction force on the dog 18, which is then exerted by the dog 18 on the mandrel 12, as indicated by the direction of an arrow 38. Thus, the mandrel 12 is put into compression between the two forces indicated by the arrows 36 and 38. The dog 16 is not in contact with either of a set of profiles 24a or 24b of the recess 24 when the dog 18 is engaged against the profile 26a.

Advantageously, as described above, the mandrel 12 is put into compression only, which is more readily handled by the aforementioned dog-type mandrels, particularly the struts of the mandrels, as opposed to tension (e.g., due to the alternating window-strut arrangement described above). That is, for example, a seal element installed upstream from the dog and/or window, with respect to the direction of loading, will prevent a portion of the mandrel being put into tension. By positioning a single seal element between a pair of dogs, the mandrel is sufficiently sealed in both axial loading directions. It is additionally noted that the assembly 10 can be further strengthened by closely setting the tolerances of the dogs 16 and 18 in their respective recesses. That is, with the close tolerances, after the mandrel 12 compresses or buckles some relatively nominal degree (e.g., 0.01 inches), the non-engaged one of the dogs will engage a profile of its corresponding recess for supporting the assembly 10 by enabling the tubular 14 to pick up the loading.

A lock assembly 40 according to another embodiment, but providing the same benefits noted above, is shown in FIG. 3. The lock assembly 40 resembles the assembly 10 in that it includes a mandrel 42 run with a tubular 44. At least one dog 46 corresponds to and is extendable through corresponding windows 48 in the mandrel 42. Struts 50 are similarly alternatingly arranged with the windows 48. The mandrel 42 is formed from two relatively movable components 42a and 42b, e.g., threaded or ratcheted together, for enabling each dog 46, initially housed in a notch 52, to be extended into a corresponding recess 54 in the tubular 44. The component 42b, could be or include, for example, a fishing neck for the mandrel 42.

In FIG. 3, the assembly 40 is loaded in the direction indicated by an arrow 56 (e.g., an up-hole pressure event). This forces the dogs 46 against a profile or face 54a of the recess 54, where the tubular 44 picks up the loading. Similar to the above, a reaction force is exerted on the dogs 46, and in turn on the mandrel 42, in the direction indicated by an arrow 58. One of ordinary skill will recognize that the system works similarly when loaded in the opposite direction, but with the dogs 46 instead engaging a profile 54b of the recess 54. A pair of seal elements 60 and 62 is disposed with one seal element on each opposite axial side of the dogs 46. If only the seal element 62 were provided and the mandrel 42 was loaded in the direction of the arrow 56, for example, the portion of the mandrel generally between the dogs 46 and the seal element 62, including the struts 50, would be put in tension. A similar outcome would result if only using the seal element 60 and loading in the direction opposite to the arrow 56. Thus, by positioning the seal elements 60 and 62 on both axial sides of the dogs 46, the mandrel 42 is advantageously maintained in compression regardless of the loading direction.

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

Claims

1. A lock assembly comprising:

a mandrel having at least one window therein;

at least one dog corresponding to the at least one window and radially extendable therethrough, wherein the at least one dog is operatively arranged for engaging at least one feature of a tubular radially disposed with the mandrel; and

at least one seal element arranged for sealing the mandrel with respect to the tubular, the at least one seal element operatively positioned with respect to the at least one dog for maintaining the mandrel solely in compression against the at least one dog during fluid pressure loading on the mandrel in either longitudinal direction with respect to the lock assembly.

2. The assembly of claim 1, wherein the loading results from a hydraulic pressure event.

3. The assembly of claim 1, wherein the at least one dog is a single dog and the at least one seal comprises a pair of seals disposed on opposite longitudinal sides of the single dog.

4. The assembly of claim 3, wherein the single dog is operatively arranged to engage a first profile of the feature of the tubular when loaded in a first direction and a second profile of the feature of the tubular when loaded in a second direction opposite to the first direction.

5. The assembly of claim 1, wherein the at least one seal comprises a single seal and the at least one dog comprises a pair of dogs disposed on opposite longitudinal sides of the single seal.

6. The assembly of claim 5, wherein the at least one feature of the tubular includes a first recess having a first profile corresponding to a first dog of the pair of dogs and a second recess having a second profile corresponding to a second dog of the pair of dogs.

7. The assembly of claim 6, wherein the first dog engages the first profile during loading in a first direction and the second dog engages the second profile during loading in a second direction opposite to the first direction.

8. The assembly of claim 7, wherein the first recess has a third profile, the second recess has a fourth profile, the first dog and the second dog operatively arranged to respectively engage the third profile and the fourth profile if the mandrel buckles during loading in the second direction and the first direction, respectively.

9. The assembly of claim 1, wherein the at least one seal is provided upstream, with respect to a direction of the loading, from the at least one dog that is engaged against a profile of the feature of the tubular.

10. A method of locking an assembly comprising;

engaging at least one dog of an assembly with a profile of a tubular radially disposed with the assembly;

loading the assembly in either longitudinal direction by pressurizing a fluid, the assembly including at least one seal element for sealing the assembly with respect to the tubular; and

maintaining the assembly solely in compression against the at least one dog regardless of the longitudinal direction of the loading.

11. The method of claim 10, wherein the assembly is maintained in compression due to the at least one seal element being positioned upstream of the at least one dog with respect to the longitudinal direction of loading.

12. The assembly of claim 10, wherein the at least one seal comprises a single seal and the at least one dog comprises a pair of dogs disposed on opposite longitudinal sides of the single seal.

13. The assembly of claim 12, wherein the tubular includes a first profile corresponding to a first dog of the pair of dogs and a second profile corresponding to a second dog of the pair of dogs.

14. The assembly of claim 13, wherein the first dog engages the first profile during loading in a first direction of loading and the second dog engages the second profile during loading in a second direction of loading opposite to the first direction.

15. The assembly of claim 14, wherein the tubular has a third profile and a fourth profile, the first dog and the second dog are operatively arranged to respectively engage the third profile and the fourth profile if the mandrel buckles during loading in the second direction and the first direction, respectively.