Well Packer Bypass Valve Seal Assembly

The invention is related to a seal assembly for an internal valve of a downhole oil well tool such as an oil well packer.

Normally, a well packer is used in oil or gas operations to seal one zone above the packer from another zone below the packer within the casing of a well bore. Packers are used for numerous operations such as zone flow testing, cementing, acidizing, and other fracturing operations.

One of the primary requirements of a satisfactory well packer is that it may be placed at a desired location and selectively set into a gripping and sealing engagement across the well casing so it can support fluid pressure from above or below an effectively isolate two zones within the casing string. When a packer is sealed in a casing, one seal is formed between an exterior portion of the packing and an interior portion of the casing and additionally another seal is formed within the packer between a mandrel and an internal valve within the packer. Obviously, the failure of either of the seals can result in fluid leakage between the separated zones within the casing which is basically undesirable. The achievement of a dependable and reliable seal within the packers internal valve has presented a difficulty in the development of well packers.

A typical packer internal valve seal assembly has a seal ring of elastomeric material that is bonded to and molded in place inside a groove in a metal seal carrier. Also, typical seal rings may have a groove formed around a mid-portion of the face seal to divide the seal into two segments

In the normal operation of a packer, fluid flows through a port immediately above the seal assembly, through the valve chamber, past the face of the seal and into the packer body cavity below while the packer is being run into or withdrawn from the well casing. In the setting operation of the packer, the packer body is displaced upward over the mandrel and the valve member on the mandrel engages the face portion of the seal ring. When this occurs, a relatively higher fluid flow rate is experienced by this seal element as the valve member moves toward the seal ring. The high fluid flow rate at this time tends to erode or deteriorate the seal capability of this valve seal rather rapidly. In extreme cases where the fluids contain particulate material and travel at relatively high flow rates, the valve seal can be eroded to the point of leaking after opening and closing the valve only two or three times. Another inherent difficulty with a bonded seal such as described above is retaining the elastomeric seal in the metal carrier ring. This problem is particularly acute for a seal shown in this patent because the dimension of the seal across the bottom of the groove is significantly larger than the depth dimension of the seal within the groove. Therefore, the broad portion of this seal can easily be pulled from the groove when high flow rates are encountered and if there is a failure in the bond or a failure in the seal material, this will allow a portion or possibly all of the seal to be dislodged from the carrier ring. The overall results of failure of a packer internal valve is that leakage can occur between the zones which are desired to be isolated within the well casing, thereby hindering the operation being performed on a particular well. Also, when these seals are damaged, the packer must be disassembled and the valve seal carrier replaced with another unit which is time consuming, troublesome and expensive for oil well field operations.

A packer valve seal assembly is provided which has a tubular seal carrier that is mountable within the valve housing of a well packer on the packer mandrel. The seal carrier assembly is constructed with a pair of annular seal elements mounted in a longitudinally spaced relation around the outer periphery of the seal carrier. The seal elements are mounted in separate grooves which have a generally cross-sectionally dovetail or an internally flared configuration which anchors the seal elements in the grooves to prevent undue flexing of the seal elements and provides excellent resistance to seal degradation. The seal carrier assembly can have a seal mounted around the inner perimeter thereof to seal between the seal carrier assembly and the associated packer mandrel.

One object of this invention is to provide a well tool or well packer valve seal assembly which overcomes the aforementioned disadvantages of the prior art devices.

Still, one other object of this invention is to provide a well packer valve seal assembly having a pair of seal elements mounted in a tubular seal carrier which are anchored sufficiently to prevent the seals from being deteriorated by high flow rates as the packer valve or other well tool valve is opened and closed.

Still, one other object of this invention is to provide a packer seal assembly which has dual seals either of which is capable of sealing the packer or well tool valve and which can be easily replaced in the field by the simple removal of a retainer ring and replacement of the seal element.

Various other objects, advantages, and features of this invention will become apparent to those skilled in the art from the following discussion, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partially cutaway elevation view of a central portion of a well packer which incorporates one embodiment, (1), of the valve seal assembly of this invention;

FIG. 2 is an enlarged partially cutaway elevation view of the valve seal assembly and associated portions of the packer shown in FIG. 1 with the valve in the open position;

FIG. 3 is an enlarged partially cutaway elevation view of one embodiment of the seal carrier assembly with the seal back-up rings, seal rings, the divider ring and the seal retainer ring displaced in an exploded relation; and

FIG. 4 is an enlarged partially cutaway elevation view of another embodiment, (2), of the seal carrier assembly with the seal back-up rings, seal ring and seal retainer ring on one end thereof displaced in an exploded relation.

The following is a discussion and description of the preferred specific embodiments of the well packer valve seal assembly of this invention, such being made with reference to the drawings, whereupon the same reference numerals are used to indicate the same or similar parts and/or structure. It is to be understood that such discussion and description is not to unduly or limit the scope of the invention.

FIG. 1 shows a portion of a well packer which has the bypass valve thereof fitted with the valve seal assembly of this invention. The portion of the packer shown, includes a slip carrier 10 with a slip 12 mounted thereon, a mandrel 13 extending through the length of the packer, a packer body 14 and one embodiment, (1), of the novel valve seal assembly of this invention is indicated generally at 16. Slip 12 is pivotally mounted on slip carrier 10 by pivot pins 20 extending from opposite sides of the slip carrier 10 and mounted through openings in opposite sides of the slip. Slip 12 is provided with two gripping surfaces 22 and 24 on opposite sides thereof to engage the interior of the well casing.

The mandrel 13 runs the length of the packer interior and includes an outwardly extending valve seal supporting shoulder 26 with a stepped lower side to engage the seal carrier and in cooperation therewith retain a seal ring 28. Shoulder 26 extends radially outward from the mandrel's smooth cylindrical outer surface 30.

Referring to FIGS. 2 and 3, the valve seal assembly includes a tubular seal carrier 54 with associated seal back-up rings, seal rings and a retainer arranged to form groove-like recesses around the exterior or peripheral portion of the seal assembly to mount and retain a pair of annular seal elements. Seal carrier 54 is a tubular member with one end portion having a radially outwardly extending ridge 56 around the periphery thereof forming an abutment 58 that faces the opposite end portion of the seal carrier. A major longitudinal portion of the seal carrier outer periphery is a non-threaded generally smooth cylindrical surface 60 extending from abutment 58 to a smaller diameter threaded portion 62 at the opposite end of the seal carrier. A groove 64 is formed around the longitudinal mid-section of non-threaded portions 60 to receive and mount a divider ring 66 that functions to separate the seal ring support structures. Divider ring 66 can be a spiral or helical ring constructed to pass around the circumference of tubular seal carrier 54 at least once with the radially inner portion thereof residing within divider groove 64 and the radially outer portion extending sufficiently beyond the cylindrical surface of non-threaded portion 60 to retain the seal back-up rings and annular seal elements and associated back-up rings in place.

In the lower portion of the seal assembly as shown in FIG. 3, back-up rings 68 and 70 are positioned on opposite sides of annular seal element or seal ring 72 and these are positioned below divider 66 when the seal assembly is put together as shown in FIG. 2. In the upper portion of the seal assembly, an additional pair of seal back-up rings 74 and 76 are positioned on opposite sides of another annular seal element or seal ring 78 and these are positioned above divider 66 in the completed valve member seal assembly. A retainer ring 80 is threadedly mounted on seal carrier threaded portion 62 and it abuts the uppermost seal back-up ring 76. Retainer ring 80 is a tubular member which is threaded on the interior of one end portion to mount with tubular seal carrier threaded portion 62. Retainer ring 80 has an inwardly extending interior ridge 82 projecting radially inwardly into a mid-portion thereof for contacting the end of tubular seal carrier 54 and retaining seal ring 28 in place against mandrel 13 as shown in FIG. 2. The exterior surface 84 of retainer ring 80 is selected to be of the same radial dimension as the exterior surface 86 of tubular seal carrier ridge 56. Also, the outer peripheral dimension of back-up rings 68, 70, 74 and 76 is selected to be approximately no larger than the outer peripheral dimension of retainer outer surface 84 and ridge outer surface 86 so the assembly will pass within the smaller diameter interior surface 36 of packer body 14.

The seal back-up rings are all generally similar in construction and are used in pairs with their associated annular seal element. These seal back-up rings are generally L-shaped with one leg radially disposed relative to the longitudinal axis of the seal carrier and the other leg disposed to lie along side a radial surface of the seal carrier. The portion of the leg which is suppose to lie along the radial surface of the seal carrier is significantly thicker than the portion of the back-up ring which is disposed transverse to the longitudinal axis of the seal carrier. This thicker portion of the back-up ring is positioned radially outward of and covering the portion of the associated seal ring.

Seal rings 72 and 78 have the same cross-sectional shape. The shape of these seal rings is generally T-shaped with a relatively thin portion 88 being longitudinally disposed relative to tubular seal carrier 54 and a thicker transverse or radially disposed portion 90 radially disposed relative to tubular seal carrier 54. The thinner longitudinally disposed portion of the seal ring is sized to fit between tubular seal carrier non-threaded surface portion 60 and the underside of the associated thicker portion of the seal back-up rings which lie in a longitudinal relation to the tubular seal carrier and spaced from surface 60. Radially disposed sealing element portions 90 are sufficiently long to extend slightly beyond the outer perimeter of the seal back-up rings when the seal assembly is completed and positioned as shown in FIG. 2. The protrusion of this portion of the seal elements is arranged so they will establish a fluid tight seal with packer body 14 when the seal elements pass within smaller diameter surface 36 in the lower portion of packer body 14. When valve member seal assembly 16 is positioned within this lower portion of packer body 14, either one of the annular seal elements will be compressed sufficiently to establish a fluid tight seal between packer body 14 and mandrel 13.

Referring to FIG. 2 with bypass valve member seal assembly 16 mounted on mandrel 13 as shown, a seal ring 28 is positioned around mandrel, adjacent to ridge 82 and within the interior of retainer ring 80 where it provides a fluid tight seal between the retainer ring and the mandrel. A groove is provided in mandrel 13 immediately below bypass valve member seal assembly 16 for the mounting of a retainer ring 92. Retainer ring 92 is used to allow only a limited downward motion of the seal assembly on the mandrel when the mandrel is raised relative in the packer body. Retainer ring 92 is selected of a radial dimension which will allow it to pass within a recess 94 around the interior of the ridge end portion of tubular seal carrier 54.

In the use of this embodiment, (1), of the bypass valve member seal assembly of this invention, it is normally mounted with a packer mandrel as shown in FIGS. 1 and 2. This embodiment of the bypass valve member seal assembly 16 is constructed so that it can be easily removed from the packer mandrel and disassembled in the field without the use of special tools or fixtures then reassembled for continued use of the packer. In normal use of the packer having this valve member seal assembly, it can be expected that after a significant use of the valve, the seal rings will have to be replaced because they are of the naturally wearing portion of the valve. It is to be noted that because of the T-shaped construction of the seal rings and the compression due to the overhanding lip of the seal back-up rings, these seal rings are retained in place in the seal assembly even when the seal assembly is exposed to damaging forces. These potentially damaging forces include opening or closing the valve when it is exposed to an extremely large differential pressure and exposing the valve to a substantially high fluid flow rate. Even if one of the seal rings is no longer able to maintain a fluid tight seal with packer body inner surface 36, the other seal ring will provide a fluid tight seal and thereby sustain the seal integrity of the valve.

FIG. 4 shows another embodiment, (2), of the bypass valve member seal assembly of this invention with such indicated generally at 100. This embodiment of the bypass valve member seal assembly includes a seal carrier 102 which has a pair of annular seal elements mounted in groove-like recesses around the exterior thereof. These seal elements are longitudinally spaced in a manner generally similar to that described above in conjunction with the other embodiment of this invention. This embodiment, (2), differs from the previous embodiment, (1), in that the seal carrier is provided with threadedly mounted retainer rings on both ends thereof to enable the seal rings to be removed from either end of the seal carrier.

In regard to seal carrier 102, it is a generally cylindrical member with an uniformed diameter interior surface 104 and a stepped exterior surface. Each end portion of seal carrier 102 has a threaded portion, 106 and 108 respectively, which extends inwardly short distance from the outer end of each end of the seal carrier. Adjacent to each of the threaded portions, 106 and 108 respectively, is a slightly larger diameter non-threaded portion 110 and 112 respectively, which extend to the center portion of the seal carrier 102 where they terminate at a radially outwardly extending ridge 114 integrally formed in the seal carrier. Ridge 114 forms an abutment for each of the separate seal back-up rings as shown. Each of the threaded end portions, 106 and 108, of seal carrier 102 are provided with threadedly mounted retainer rings, 116 and 118 respectively, for securing the seal back-up rings and seal rings on the respective end portions of the seal assembly. In the lower portion of FIG. 4, a pair of seal back-up rings 120 and 122 are provided on opposite sides of an annular seal element or seal ring 124. On the upper portion of FIG. 4, another pair of seal back-up rings 126 and 128 are provided on opposite sides of their associated seal element or seal ring 130. The seal back-up rings and seal rings shown in FIG. 4 have the same structural features as the seal back-up rings and seal rings described above in conjunction with the first embodiment, (1), therefore, a complete description of the structural details of these rings will not be presented again.

In assembly of the components of bypass valve member seal assembly 100, the seal back-up rings and their associated seal elements are placed on the outer periphery of the seal carrier and the relationship shown in the lower portion of FIG. 4. Retainer rings 116 and 118 are then threadedly mounted with threaded portions 106 and 108. A pair of notches are provided on opposite sides of the outer end of each retainer ring so that a suitable lug wrench can be used to tighten the retainer ring. In the cutaway portion of FIG. 4, retainer ring 116 has the visible notch indicated at 132 and retainer ring 118 has the visible notch indicated at 134.

It is to be noted that if desired, retainer rings 116 and 118 can be constructed without the notches and a circumferentially compressive wrench or similar hand tool used to install and remove the retainer rings. When this seal assembly is completed and ready for use, the outer periphery of seal rings 124 and 130 extends slightly radially outward of the outer peripheral surface of the associated seal back-up rings, the retainer rings and ridge 114 so that it can make sealing contact with portions of the valve structure in which it is installed.

Bypass valve member seal assembly 100 is constructed so that it can be mounted with the packer mandrel having a construction generally similar to that shown in FIGS. 1 and 2 only with sealing between the seal carrier and the mandrel accomplished by means other than the sealing means shown in FIGS. 1 and 2. Also, seal assembly 100 can be mounted with well tools other than a packer for which may incorporate in their construction a seal carrier support structure which will mount the seal assembly in operable relation to an annular valve seat assembly which in operation of the tool will engage sealing elements of this valve member seal assembly. In the use of both of the embodiments of the novel valve member seal assembly of this invention, it has been found that the seal elements can be easily replaced under field conditions in the event they are deteriorated sufficiently to begin to leak. Also, in the use of this seal assembly in packers, it has been found that using the pair of closely spaced seal elements retained in the above described structure virtually eliminates the problem of having the seal elements blown out or severely damaged due to normal operation of the packer. Additionally, it has been found that in the event one of the seal elements is deteriorated sufficiently to begin leaking, the remaining seal element is sufficient to prevent fluid leakage through the packer valve for normal operating pressures where the high pressure is either above or below the packer.