Abstract:
In a release system for a packer the release ring is minimally exposed in the wellbore and is actuated by a release tool, which comprises a collet and cone with a relative movement feature. In the preferred embodiment, the release ring has alternating cuts and a built in radially outward bias. The ring is held in locked position by bands, which are broken by the action of the releasing tool.

Description:
FIELD OF THE INVENTION 
     The field of this invention is a releasing system for downhole packers and more particularly, a system where the release mechanism is protected from accidental release and damage from flowing fluids. 
     BACKGROUND OF THE INVENTION 
     In the past, downhole packers were released in three different ways. Dogs were unsupported to let the body be extended for release. Collets became unsupported to have the same effect. Finally, the packer could be cut downhole to allow release. FIGS. 1 a - 1   c  illustrate a prior art mechanically set packer with a collet release system. A setting tool (not shown) pushes down on setting sleeve  10  while pulling up on the top sub  12  of mandrel  14 . The setting sleeve  10  pushes down on the sealing elements  16 , the upper cone  18  and the slips  20 , while the mandrel  14 , through collets  22 , pulls up on the lower cone  24 . The set position is held by body lock ring  26 , which works like a ratchet to keep the set packer from relaxing. As seen in FIGS. 1 c  and  2 , a support sleeve  28  is held on to the collets  22  by shear pins  30 . In the position shown in FIG. 1 c  the support sleeve transmits the upward pull force from the top sub  12  to the lower cone  24  during the setting procedure. To release the packer, a release tool (not shown) is run downhole to engage the support sleeve  28  and pick it up so as to break shear pins  30  and to undermine the contact between the collets  22  and bottom sub  32  (see FIG.  3 ). The releasing tool brings up the support sleeve  28  against the mandrel  14  to allow the slips  20  to be undermined as the upper cone  18  is pulled out from under them. In a similar manner, the elements  16  are allowed to relax. 
     In a similar manner, the prior art design of FIGS. 4 and 5 operated to allow the packer to set and, later, to release, when a release tool (not shown) moved up release sleeve  34  undermining the segmented dogs  36  for a release from the bottom sub  38 . These structures were also used with hydraulically set packers. 
     The potential problem with these designs is the exposed placement of the support sleeve  28  or the release sleeve  34 . Lowing well fluids can cause damage due to erosion or corrosion. Additionally, tools are frequently run through such packers to actuate other devices below the packer. These tools could, inadvertently, engage the support sleeve  28  or the release sleeve  34  and trigger a release of the packer. This problem could be avoided with another known design which requires the packer to be cut loose after being set downhole. This technique is complicated and requires very experienced personnel to perform the operation. This technique also generates cuttings which can be left in the well and the packer is destroyed in the process, preventing reuse. 
     The present invention presents a unique mechanism for release which overcomes the drawbacks of the prior art as described above. The release mechanism is minimally exposed to the wellbore to give it protection from well fluid attack and accidental release from contact by other tools. Additionally, the packer is simply released and can be reused. These and other advantages of the present invention will be more readily understood from a review of the description of the preferred embodiment, which appears below. Other known packer release designs are illustrated in U.S. Pat. Nos.: 3,311,171; 3,361,207; 3,976,133; 4,216,827; 4,436,150; 4,518,037; 4,565,247; 4,664,188; 5,333,685; 5,718,291; and 5,787,982. 
     SUMMARY OF THE INVENTION 
     A release system for a packer is disclosed. The release ring is minimally exposed in the wellbore and is actuated by a release tool, which comprises a collet and cone with a relative movement feature. In the preferred embodiment, the release ring has alternating cuts and a built in radially outward bias. The ring is held in locked position by bands, which are broken by the action of the releasing tool. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 a - 1   c  are a sectional elevation of a prior art tool using collet release, shown in the run in position; 
     FIG. 2 is a detailed view of the collet release system shown in prior art FIG. 1 c,  shown it the set position for the packer; 
     FIG. 3 is the view of the prior art tool shown in FIG. 2, but shown in the released position; 
     FIG. 4 is an alternative prior art design of a releasing assembly, shown in the set position; 
     FIG. 5 is the view of FIG. 4 shown in the released position; 
     FIG. 6 is one embodiment of the present invention, shown in section, just prior to release with the releasing tool; 
     FIG. 7 is the view of FIG. 6 in the released position; 
     FIG. 8 is a section view of the release ring of the preferred embodiment of the invention; 
     FIG. 9 is a view along lines  9 — 9  of FIG. 8; 
     FIG. 10 is a view along lines  10 — 10  of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In a first embodiment of the invention, shown in FIG. 6, the pickup force to set the packer is transmitted from sleeve  40  to sleeve  42  through release ring  44 . It should be noted that FIG. 6 illustrates the same area of the packer as FIGS. 2-5 but it represents one embodiment of the present invention to replace those prior art assemblies. Ultimately, sleeve  42  is connected to bottom sub  46  in an area off the right side of FIG.  6 . Bottom sub  46  exerts an upward force on the lower cone to help set the slips and the element in the manner described for the prior art devices. What is different is how the setting force is transmitted and how the set is later released. In FIG. 6, the release ring is made of independent segments each having a tab  48 , which extends into groove  50  of sleeve  40 . A matching tooth or serration or other engagement pattern  52  helps retain the release ring  44  to the sleeve  40 . Similarly, a similar structure  54  helps retain the sleeve  42  to the release ring  44 . Initially, bolts  56  hold sleeve  40  to release ring  44  and bolts  58  retain the release ring  44  to sleeve  42 . In FIG. 6, the retrieving tool is in position but has not yet been actuated. The retrieving tool R has a movable cone  60  adjacent a series of collets  62 . When the retrieving tool R is actuated, the cone  60  moves relatively to the collets  62  pushing the collet heads  64  against surface  66  of release ring  44 . There is a clearance space  68 , which closes up as the release ring  44  has its segments pushed outwardly. 
     As shown in FIG. 7, actuation of the releasing tool R disengages the engagement patterns  52  and  54  but tab  48  is still in groove  50 . Because the tab  48  is still engaged in groove  50 , the segments that make up the release ring  44  remain connected to sleeve  40  and do not fall to the bottom of the wellbore. The release of the engagement patterns  52  and  54  allows the packer to be stretched out and retrieved in the known manner, using the retrieval tool R. Those skilled in the art will appreciate that each segment of release ring  44  has two bolts  56  and  58  to initially secure the engagement patterns  52  and  54  which are on it, respectively to sleeves  40  and  42 . As shown in FIG. 6, surface  66  is flush in the passage  70  leaving it less likely to be actuated by tools going further downhole to operate other equipment. The limited exposed area of surface  66  further reduces the potential harmful effects from erosion or corrosion from passing well fluids. The engagement patterns  52  and  54  are completely out of the main flowpath. Additional seals can be optionally added to fully isolate the engagement patterns  52  and  54  from the moving well fluids. Once the packer is removed, it can be redressed for further use by putting the components back together as shown in FIG.  6 . 
     The preferred embodiment is shown in FIGS. 8-10. In this version the release ring  44 ′ takes the place of the segments that made up release ring  44 . Engagement patterns  52 ′ and  54 ′ are still used with the release ring  44 ′. Rather than being segments, release ring  44 ′ is a cylinder having alternating longitudinal notches  72  and  74  which begin, respectively, at opposite ends  76  and  78  of release ring  44 ′. An outward radial bias is built into release ring  44 ′ toward the clearance space  68  (see FIG.  6 ), when release ring  44 ′ is used in lieu of the segments that make up release ring  44 . Overlaying the release ring  44 ′ are bands  80  and  82  to urge radial inward movement against a spreading force by the retrieval tool R against surface  66 ′. The use of the bands  80  and  82  allows tab  48  and groove  50 , used of segments that made up release ring  44  to be eliminated in the preferred design of release ring  44 ′. In other respects, the operation of the two embodiments of the invention are the same. 
     Those skilled in the art will appreciate that both embodiments of the invention described above present a minimal area in the passage  70  for the release mechanism. The flush mounting reduces the chance of an accidental release and minimizes the erosive and corrosive effects of flowing fluids. The size of the passage  70  can be maximized. The engagement patterns, such as  52 ′ and  54 ′, can be isolated from fluids flowing through passage  70 . Minor impingements on to surface  66 ′ are unlikely to actuate a release. Use of the flush mounted surface  66 ′ makes it simpler to release, when that operation is desired, than even the design shown in FIGS. 6 and 7 and certainly release is easier than the prior art techniques illustrated in FIGS. 2-5. Surface  66 ′ can also be slightly recessed. This makes it easier to properly locate the releasing tool R. 
     The above description of the preferred embodiment is merely illustrative of the optimal way of practicing the invention and various modifications in form, size, material or placement of the components can be made within the scope of the invention defined by the claims below.