Downhole Lubricator and Method

The field of this invention relates to downhole shutoff valves, particularly valve assemblies suitable for shutting off formations in under-balanced wells to allow for uphole assembly of equipment for subsequent operations in the wellbore.

During the life of the well, completion work may need to occur to allow access to hydrocarbon reservoirs at various elevations, or for other reasons. If a well has access to a hydrocarbon reservoir which creates a pressure in the wellbore, access into the wellbore above this reservoir needs to occur with the lower reservoir isolated. Some wells are under balanced, meaning that, while the completion work is ongoing, the formation pressure from the producing reservoir is not offset by a column of liquid in the wellbore. Instead, in oil or gas wells the pressure from the formation needs to be isolated positively with two shutoffs before the wellhead can be opened up so that further completion work can occur. In the past, this has been accomplished with a lubricator above the wellhead. A lubricator is a chamber with valves on top and bottom which is limited in height to about 60'-80' so that tools can be hoisted into the top of it. Using lubricators limits the length of a downhole assembly and creates delays if long strings of such equipment as perforating guns are required. Single flapper subsurface safety valve arrangements are not satisfactory since dual isolation is required before the under-balanced wellbore can be accessed through the wellhead while meeting existing regulations. In a typical installation, a pair of control lines are run from the surface into a portion of the casing for operation of a known single flapper subsurface safety valve. Such control lines are used in the present invention to operate a removable valve assembly to allow long strings of tools to be assembled in the wellbore through an open wellhead.

If dual valves are used, each must be tested. The problem in the past with a dual valve arrangement has been that once the lower valve is closed and tested, the upper valve is not exposed to well pressure and cannot be tested from below. This invention solves this problem by testing the upper valve from above.

The object of the present invention is to provide a dual shutoff system with facilities to pressure test the two shutoffs to ensure their integrity. The system employs existing control line connections and has as another of its objectives that it be removable.

The invention is an assembly which is run into the wellbore to straddle pre-existing control line connections used normally for actuation of a sleeve for a single subsurface safety valve. The lower flapper is closed through the use of one of the control lines. It is then tested against formation pressure to make sure that it holds. Upon determination that the lower flapper is holding, the upper flapper is shut off using the other control line. By adding additional pressure to the control line for the lower sleeve, further movement of the lower sleeve is obtained to urge another sleeve into contact with the upper flapper to provide support for it so that it can be tested from above. Once the two flappers have been tested, uphole assembly in the wellbore can begin through the wellhead in the zone above the tested valves. Once assembled, coiled or rigid tubing or wireline can be advanced sealingly through the wellhead as the assembly is lowered past the flappers which are now allowed to open. The flapper assembly is eventually removed.

FIGS. 1a-1e are a sectional elevational view of the assembly installed in the casing with both flappers open.

FIGS. 2a-2d are the sectional elevational view of FIGS. 1a-1e with the running tool removed and the lower flapper in the closed position.

FIGS. 3a-3d are the tool, as shown in FIG. 2, with both flappers closed and the upper flapper ready for test.

FIGS. 4a-4e are the run-in position of the preferred embodiment for support of the upper flapper.

The production tubing 10 is illustrated in part in FIGS. 1a-1d. Typically, the production tubing 10 has control lines 12 and 14 which run to the surface for actuation of a single subsurface safety valve (not shown). The production tubing 10 generally has an internal profile 16, which is generally used for latching in the normal assembly for a subsurface safety valve. In the present invention, the flapper assembly 18 extends from upper end 20 to lower end 22. The flapper assembly 18 is run in with a known running tool 24. The running tool 24 has a series of collets 26 which engage a recess 28 near the upper end 20 of the flapper assembly 18. The collets 26 are supported by a movable sleeve 30, and in the position shown in FIG. 1a, the running tool 24 is latched into and locked to the upper end 20 of the flapper assembly 18.

The flapper assembly 18 also has a series of dogs 32, which have a front profile similar to the profile 16 in the production tubing 10 so as to land and latch the flapper assembly 18 to the production tubing 10. The latched position is shown in FIG. 2b, where tapered surface 34 has advanced under dogs 32, effectively camming them into the profile 16.

The flapper assembly 18 has a series of external seals 36, 38, and 40 which align themselves appropriately straddling inlets 42 and 44. Control line 12 is connected to inlet 42, while control line 14 is connected to inlet 44. Seals 38 and 40 straddle inlet 44, while seals 38 and 36 straddle inlet 42.

The flapper assembly 18 includes an upper flapper 46 and a lower flapper 48. While flapper-style valves are illustrated, other types of valves are within the scope of the invention and within the scope of the word "flapper" as used in this application. Flapper 46 pivots around pivot 50 and is urged to the closed position, such as shown in FIG. 3b, by spring 52. Upper sleeve 54 is normally urged downwardly to the position shown in FIGS. 1b and 1c by spring 56. Pressure applied to inlet 42 through control line 12 overcomes the force spring 56 lifting the sleeve 54 upwardly which, in turn, allows the flapper 46 to snap shut, as illustrated in FIG. 3b.

A similar arrangement exists for the lower flapper 48. Flapper 48 pivots around pivot 58 and is urged into the closed position by spring 60. Lower sleeve 62 prevents rotation of flapper 48 due to the force of spring 64. Fluid pressure applied to inlet 44 from control line 14 acts to shift up sleeve 62 against the force of spring 64 to allow spring 60 to close the flapper 48, as shown in FIG. 2d. Sleeve 62 has an upper end 66 which, in the run-in position, as shown in FIGS. 1c and 1d, is at a distance from tapered surface 68 on support sleeve 70. As seen by comparing FIGS. 1c and 1d with 2b and 2c, the opening of the lower flapper 48 results in movement of sleeve 62 in an upward direction so that the upper end 66 makes contact with tapered surface 68. The support sleeve 70 is initially held to the body 72 of the apparatus of the present invention. The upper end of the support sleeve 70 comprises a plurality of protrusions or collets 74 which are normally retained by an annularly-shaped recess 76. The support sleeve 70 has an upper end 78 which, as shown in FIG. 3b, supports the flapper 46 when it is in the closed position.

The operation of the apparatus and method of the present invention is as follows. The running tool 24 is used to insert the flapper assembly 18 into the production tubing 10. The dogs 32 are engaged into the profile 16. Pressure is applied through control line 14 into inlet 44. The application of this pressure shifts the sleeve 62 upwardly, allowing spring 60 to rotate flapper 48 about pivot 58. The movement of sleeve 62 and flapper 48 can be readily seen by comparing FIG. 1d and 1e to FIG. 2c and 2d. It should be noted that the pressure applied to the control line 14 is approximately in the order of 1,000 pounds. This pressure is sufficient to move up the sleeve 62, but is less than the pressure ultimately required to move sleeve 62 to the point where it moves support sleeve 70 out of contact with recess 76. There is a lost motion between sleeves 62 and 70. That is, that sleeve 62 while engaged to sleeve 70 can move a fixed distance before both sleeves move in tandem.

This is true in both directions of movement of sleeve 62.

With the lower flapper 48 closed, its sealing off of the production tubing 10 can be measured at the surface using the pressure created by the live well in which the production tubing 10 is located. If such a test reveals that there is no leakage, pressure is then applied to the control line 12 which is connected to inlet 42. Sleeve 54 is shifted upwardly due to the applied pressure at inlet 42 which allows spring 52 to pivot flapper 46 about pivot 50. This movement can be seen by comparing FIG. 2d to FIG. 3d. When the upper flapper 46 is closed, the well has already been isolated down below by the prior closure of flapper 48. Accordingly, pressure created from the formation cannot be used to test the sealing engagement of flapper 46 from below if flapper 48 is already closed.

Accordingly, the support sleeve 70 now comes into play as pressure is further increased on control line 14 connected to inlet 44. The pressure may be increased to, for instance, 2,000 lbs from 1,000 lbs on control line 14. This pressure increase will urge sleeve 62 upwardly until a resultant force is applied to support sleeve 70 when upper end 66 engages tapered surface 68. The position of the components just before movement of support sleeve 70 is shown in FIG. 2b. Upon increase in pressure to control line 14, the support sleeve 70 is driven upwardly until it contacts the underside 80 of flapper 46. In order to get to this position, the applied force to the support sleeve 70 exceeds the retention force of the protrusions 74 in the annularly-shaped recess 76. Now, with the upper end 78 in contact with the underside 80 of the flapper 46, pressure from above can be applied to see if any leakage occurs. Once it is determined that upper flapper 46 is also in a sealing mode, the entire distance in the production tubing 10 above the upper flapper 46, which is now doubly isolated from well pressure, can serve as a lubricator for assembly of tools, such as perforating guns. Normally, if a surface-mounted lubricator is used, the string that is assembled through a lubricator is limited to approximately 60-80 feet. If perforation is to take place in the wellbore in an under-balanced condition, and the perforation is over an interval of say 1,000 feet, the use of a lubricator would inordinately delay accomplishing such a perforation job as only 60-80 feet of guns can be assembled at a time through the lubricator and run into the well on coiled tubing or wireline.

Another option is to simply kill the well with heavy fluids, but a risk occurs that in the future when such fluids are removed damage could occur to the formation which could affect the future performance of the well. Instead, using the apparatus of the present invention with the flapper assembly 18 in the wellbore and the production tubing 10 in a fully tested condition with flappers 46 and 48 closed and sealing, the entire distance from the surface to the upper flapper 46 can be employed to assemble any length of equipment within that interval. In a typical installation, the connections 42 and 44 are between 1,000-2,000 feet from the surface. Accordingly, a string having that kind of a span can be assembled through the wellhead and the 1,000-2,000 foot span above the closed flappers 46 and 48 in effect becomes a very long lubricator in lieu of one typically used above ground, which has height limitations due to rig heights, which are used to insert items into the top of such surface-mounted lubricators. Once the assembly is put together and run-in through the wellhead (not shown) and supported by, for example, coiled tubing, the assembly, now sealingly isolated at the wellhead, can be lowered through flappers 46 and 48 which are opened by removal of pressure from control lines 12 and 14. It should be noted that the removal of pressure in control line 12 starts the flapper 46 rotating counterclockwise and pushes down support sleeve 70. Additionally, removal of pressure from control line 14 allows the spring 64 to pull sleeve 62 downwardly. Sleeve 62 and sleeve 70 can be configured such that when sleeve 62 reaches the position shown in FIGS. 1c-1e, it pulls down with it sleeve 70. Thus, the preferred sequence of operations is removal of pressure from control line 14 which allows spring 64 to push down sleeve 62 to open flapper 48. On the way down, sleeve 62 carries with it support sleeve 70. Thereafter, pressure is removed from control line 12 which allows spring 56 to push down sleeve 54 to open upper flapper 46. The coiled tubing which supports the assembly that has earlier been run above the two flappers 46 and 48 is in itself mounted in a way that it is sealed at the wellhead. Accordingly, the assembly that has been put together above flappers 46 and 48 can now be positioned as desired in the wellbore. For example, a series of perforating guns that is 800-1,500 feet long, for example, can be assembled above closed flappers 46 and 48 with the wellhead open and the well, itself, in a live condition. For removal, the above process is reversed, i.e., the assembly of the perforating guns is brought above flappers 46 and 48 and they are allowed to close. They can then be tested and excess pressure vented at the wellhead. The gun assembly can then be removed. It should be noted that the flapper assembly 18 can at the conclusion of the operations with, for example, the gun assembly, can be removed from the wellbore and a standard subsurface safety valve installed which can be operated with control lines 12 and 14.

Referring to FIGS. 4a-4e, the preferred embodiment of the support of the upper flapper 46 is disclosed. The numbers will be repeated where the structures are the same with new numbers assigned to different components or configurations of the parts previously described. Spring 64 acts on tab 90 which is attached to the lower sleeve 62. In that manner, spring 64 biases sleeve 62 downwardly to hold the lower flapper 48 open as shown in FIG. 4e. When pressure is first applied to control line 14 and into inlet 42, the sleeve 62 cannot initially move because raised surface 92 traps collet 94 against a shoulder 96. The collet or collets 94 are downwardly biased by spring 98 which is itself supported from ring 100. Ring 100 is mounted to the sleeve 62. Below the collets 94 is a stack of Belleville washers 102. The stack of Belleville washers is supported by ring 104 which is connected to sleeve 62. As pressure increases in control line 14, the sleeve 62 will try and rise up, but its upward movement will be prevented because the collets 94 are trapped by shoulder 96.

Eventually upon application of sufficient pressure, the Belleville washers 102 will be compressed flat to allow the collets 94 to move downwardly into recess 106 on the sleeve 62. When that occurs, the collets 94 are no longer trapped by shoulder 96 and are free to move upwardly until they encounter shoulder 108. Thus, the sleeve 62 moves in tandem with collets 94 when the collets 94 are within the recess 106. As soon as the collets 94 are clear of the shoulder 96, spring 98 pulls the collets back up against the raised surface 92. In that position, the collets 94 encounter the shoulder 108. Accordingly, with the collets 94 again supported after clearing the shoulder 96, they lock again against shoulder 108. By the time the collets 94 have become trapped on shoulder 108, the sleeve 62 is moved a sufficient distance to allow the lower flapper 48 to open. However, during this time, the support sleeve 70 has not moved because dogs 110 engage groove 112. The upper end 66 of sleeve 62 supports the dogs 110 into engagement with the recess of groove 112. Accordingly, the sleeve 62 is free to move up the distance between the upper end 66 and the shoulder or tapered surface 68 on support sleeve 70. In order to move the support sleeve 70, the pressure must be increased on control line 14. This increase in pressure once again allows the collets 94 to move into recess 106 as the pressure is placed on sleeve 62 to move further upwardly. Once sleeve 62 moves upwardly sufficiently to have the collets 94 once again retreat into recess 106, the shoulder 108 can be cleared by collet 94. Thus, with collet 94 once again within recess 106, sleeve 62 moves further upwardly until recess 114 on sleeve 62 comes up against the dogs 110. At that time, the dogs 110 become unsupported and move out of recess or groove 112. With pressure continuing to be applied at control line 14, the sleeve 62 moves upwardly now in contact with shoulder 68 of support sleeve 70. Support sleeve 70 continues to move until it encounters the upper flapper 46 which by that time has already been closed due to application pressure to the upper control line 12. When the support sleeve 70 is in the position of supporting the upper flapper 46 in the closed position, a test on the upper flapper from the surface can be accomplished as described previously.

When it is time to close the upper flapper 46 and lower flapper 48, the pressure is removed from the lower control line 14. Initially, the support sleeve 70 moves downwardly with the lower sleeve 62. When the dogs 110 again become aligned with recess 112, the sleeve 62 moves relatively to the support sleeve 70 thus camming the dogs 110 into groove 112. From that point on the support sleeve 70 does not move any further. Eventually, the collets 94 encounter again the shoulder 108. However, without pressure on control line 14, the return spring 64 provides sufficient force to overcome spring 98 to allow the collets 94 to move into recess 116. With the collets 94 in recess 116, the can clear the shoulder 108. As soon as the collets 94 pass the shoulder 108, the spring 98 pushes them back out against raised surface 92. At that point, the sleeve 62 continues to move further downwardly under the power of return spring 64. Eventually, the collets 94 encounter the shoulder 118 and the same procedure occurs where the collets 94 are again forced into recess 116 to clear shoulder 118. After the collets 94 clear shoulder 118, spring 98 once again resets the collets in opposition to raised surface 92 which in turn traps the collets 94 against shoulder 96 to reassume the run-in position shown in FIGS. 4a-4e.

Those skilled in the art can see that in this preferred embodiment, the support sleeve 70 is locked out from movement until a discrete amount of movement of the support sleeve 62 occurs. It takes a predetermined pressure to compress the Belleville washers 102 to initiate any movement at all. The amount of washers in the stack 102 determines how much pressure at control line 14 is required to initially allow the collets 94 to move around the shoulder 96 to initiate initial movement. If pressure is held only at a predetermined level, the sleeve 62 stops its movement at a predetermined position which is denoted by the placement of shoulder 108. Thus, it takes a further increment in pressure to make the collets 94 once again overcome the force of the Belleville washer stack 102, which moves in tandem with the collets 94 and the sleeve 62. When that higher pressure increment is applied with the collets 94 trapped against shoulder 108, the further movement of sleeve 62 occurs, which allows the support sleeve 70 to become unlocked due to the unsupporting of dogs 110 when groove 114 is in alignment with them. When this occurs, the support sleeve 70 moves up finally into position to support the by-then-closed upper flapper 46.

It will be appreciated that the net result of both embodiments is the same, i.e., that the upper flapper 46 is supported by the support sleeve 70. However, the mechanical execution is slightly different, and the embodiment in FIGS. 4a-4e is preferred.

It should be noted that the individual operation of rotatably mounted flappers, such as 46 and 48, using spring-biased sleeves, is a technique that has been known in the art. The present invention employs the technique of actuation of flappers to create, in effect, a lubricator which can be leak-tested and which has approximately a length of 2,000 feet to greatly facilitate operations at the wellhead when further completion work is necessary.

The low profile of the flapper assembly 18 should also be noted. Often it is important to provide as much clearance as possible for the assembly that is put together above flappers 46 and 48. The apparatus and method of the present invention allows testing of two shutoffs for sealing integrity. Once such sealing integrity has been determined, applicable laws and regulations that require two certain shutoffs before opening of the wellhead for further operations are met. By use of the support sleeve 70, the problem of how to test a second flapper has been solved. It should be noted that while the use of a support sleeve 70 to hold flapper 46 in the closed position for a test from above has been disclosed, it is within the purview of the invention to use other techniques to temporarily hold closed the upper flapper 46 for a pressure test from the surface.

It should be noted that if the flapper closure sequence is reversed and flapper 46 is closed first and tested, it must be reopened in order to test the lower flapper 48. Once the upper flapper 46 is reopened, the previous test that has been done on it is invalid for purposes of compliance with regulations that require two positive shutoffs. Accordingly, the sequence described above is used where the lower flapper 48 is tested with well pressure and the upper flapper 46 is tested from above with a support holding it closed.

It should be noted that other ways to support the flapper 46 in the closed position apart from sleeve 70 can be employed. Such techniques may include any type of control on the pivot pin 50 to keep it momentarily from rotating during the test or the use of other styles of valves which can hold the closed position with a sleeve such as 70 or by other means.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.