BACKGROUND
In the downhole drilling and completion arts, sealing of various things such as an annulus between a mandrel or basepipe and a casing, for example is a common requirement. Many different types of seals have been developed and have used many different types of material and/or combinations of material. More recently, high expansion metal seals have become of interest to the industry yet while they suffer little from the deleterious effects of the downhole environment and relatively easily resist mechanical insults such as pressure inversions, extrusion, and the ravages of time, they present greater difficulty with regard to establishing a competent seal to begin with. Various means have been used to assist in the creating of the seal each having effective success to some degree.
None of the known solutions has proven a panacea in all situations and consequently, the art still seeks alternative solutions and well receives those proposed.
SUMMARY
A downhole seal includes a seal body; two or more pips extending in a direction from the seal body associated with an intended sealing surface, the two or more pips defining nonparallel facing surfaces when in a run in position.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings wherein like elements are numbered alike in the several Figures:
FIG. 1 is a schematic cross sectional representation of a prior art seal in a run in position;
FIG. 2 is a schematic cross sectional representation of the same seal shown in FIG. 1 but in a set position;
FIG. 3 is a schematic cross sectional representation of a seal configuration as disclosed herein in a run in position;
FIG. 4 is a schematic cross sectional representation of the same seal shown in FIG. 3 but in a set position;
FIG. 5 is a schematic cross sectional representation of another seal configuration as disclosed herein in a run in position;
FIG. 6 is a schematic cross sectional representation of the same seal shown in FIG. 5 but in a set position;
FIG. 7 is a schematic cross sectional representation of another seal configuration as disclosed herein in a run in position;
FIG. 8 is a schematic cross sectional representation of the same seal shown in FIG. 7 but in a set position;
FIG. 9 is a schematic cross sectional representation of another seal configuration as disclosed herein in a run in position;
FIG. 10 is a schematic cross sectional representation of the same seal shown in FIG. 9 but in a set position;
FIG. 11 is a schematic cross sectional representation of the seal configuration shown in FIG. 3 with an optional sleeve, as disclosed herein in a run in position;
FIG. 12 is a schematic cross sectional representation of the same seal shown in FIG. 11 but in a set position; and
FIGS. 13-20 are schematic cross sectional representations of alternate elastomer configurations for the seal embodiments of FIGS. 3-12.
DETAILED DESCRIPTION
In order to enhance understanding of the invention disclosed herein initial reference will be made to the prior art, represented in FIGS. 1 and 2. A prior art seal 10 includes pips 12 and 14. The pips together define parallel facing surfaces 16 and 18. Once the seal 10 is set, the pips 12 and 14 are moved to a position illustrated in FIG. 2, with the surfaces 16 and 18 moving to a splayed open position as shown. In the prior art this was considered a positive occurrence and hence is the state of the art.
Referring now to FIGS. 3 and 4, a first embodiment of the seal concept disclosed herein is illustrated. A seal body 110 comprises a relatively rigid material such as a metal material. In one embodiment the material is a steel alloy such as stainless steel or inconel. The seal body 110 includes a set of depending pips 112 and 114 that extend radially relative to an axis of the seal body 110 and in one embodiment, as illustrated, extend radially outwardly. Significantly, the pips 112 and 114 each define nonparallel facing surfaces 116 and 118, respectively. These surfaces are oriented to generally oppose each other but they are not parallel to each other in the run in condition. Moreover, as can be appreciated from the Figures, the surfaces grow closer to one another as distance from the seal body 110 increases. The surfaces 116 to 118 form an acute angle with respect to a centerline 119 of the seal body as displayed in the Figures. Pips having angled surfaces, as illustrated, more reliably achieve metal-to-metal contact with a casing inside surface (casing ID) 120. Further the angled surfaces 116 and 118 help to minimize a radial extrusion gap between the pip 112 or 114 contact surface 122 or 124, respectively, and casing ID 120 than does the prior art seal shown in FIGS. 1 and 2. The acute angle of the pips also helps to self-energize the seal, in an embodiment where soft material filler 130 is included, with the application of differential pressure. The acute angle of the pips allows for a larger cross sectional area between the two pips for a given dimension between distal ends 121 and 123 of the pips, which will provide larger volume of soft material than the geometry of the prior art such as illustrated in FIG. 1. The performance increase is due to the pips 112 and 114 having higher contact pressure against a casing ID 120 or to the pips 112 and 114 attaining a final set position in closer proximity to the casing. As can be appreciated in FIG. 4, the orientation of the pips 112 and 114 creates an acute angle between surface 116 and 120 when measuring the angle toward the left side of the drawing and an acute angle between surface 118 and 120 when measuring the angle toward the right side of the drawing.
In another embodiment, referring to FIGS. 5 and 6, the configuration of FIGS. 3 and 4 is repeated except for the addition of an additional pip 126. The additional pip 126 is configured to contact the casing 120 as shown in FIG. 6. The advantages to adding a center pip is that it offers the potential of a third metal-to-metal contact point or reduced extrusion gap and it controls the set volume of soft material 130, which prevents excessive squeeze.
In another embodiment, referring to FIGS. 7 and 8, the configuration of FIGS. 5 and 6 are repeated except the pips 128 and 131 have a reduced diameter (reduced prominence) that is less than the diameter of the center pip 126 (prominent pip). The advantage to reducing the diameter of the outer pips 128 and 131 is that metal-to-metal contact between the center pip 126 and the casing ID 120 is even more reliably achieved. The pips 128 and 131 still provide for soft material filler anchoring to help prevent washing away of the soft material. In this embodiment however, the shorter pips encourage the soft material to flow between the pips and the casing ID 120. This helps with sealing small irregularities in the surface 120. Further, it is to be appreciated that in this embodiment the angled inner surfaces of the pips of the foregoing embodiments may be used but are permissive rather than required. Stated alternatively, in embodiments with reduced prominence pips, the pips need not have the angled surfaces 116 and 118 as in the foregoing embodiments but could be configured with surfaced 16 and 18 as in the prior art.
In another embodiment, referring to FIGS. 9 and 10, the configuration of FIGS. 3 and 4 is repeated except a span surface 134 between pips 112 and 114 is not perpendicular to the centerline 119 of the seal but rather has a concave shape with respect to the centerline of the seal as illustrated. The concavity of span surface 134 alters the set volume of the seal 110 and allows for greater selection in soft material volume. It is to be understood however, that the volume of the area defined by the pips, surface 134 and casing surface 120 will change during setting of he seal 110 and therefore consideration of the amount of soft material is important to ensure that it does not prevent metal to metal contact of the seal with the casing 120, something that can occur as a result of excessive squeezing of the soft material.
In all embodiments FIGS. 3-10, an additional optional sleeve 136 is contemplated. Referring to FIGS. 11 and 12, an illustration of a seal configuration like that of FIGS. 3 and 4 is used to illustrate the sleeve 136. The illustration is certainly by way of illustration rather than limitation since the sleeve may be used on any of the embodiments disclosed herein or others. In one embodiment the sleeve 136 comprises non-metallic material although metallic material having appropriate structural characteristics could be substituted. Structural characteristics that are desired include toughness to resist borehole impacts during running and softness to promote sealing at pip contact surfaces 122 and 124. The sealing function of the sleeve 136 occurs similarly to that of the soft material 130 in that it flows into small irregularities at casing surface 120 but is located at the pips as opposed to between the pips.
As has been alluded to hereinabove, each of the embodiments disclosed may be used with or without a soft material 130. Each of the foregoing seal configurations used alone will create a reliable seal. These configurations when endowed with a softer material 130 (see FIGS. 13-20) than the material from which the seal itself is constructed, that softer material being positioned between pip 112 and pip 114 or 128 and 130 exhibit different sealing properties that may be helpful in tubular structures having a pitted surface, for example. Softer materials contemplated include but are not limited to nonmetallic materials such as polytetrafluoroethylene, rubber, plastic, and soft metallic materials such as lead, gold, silver, etc. Each of these materials tends to flow relatively easily under stress. They are therefore helpful in ensuring sealing in smaller discontinuities of the sealing surface. The configurations of the pips as described above enhance the utility and reliability of these softer materials by helping to keep them contained between the pips rather than to allow the material to flow to a position where it is between the pips and the casing 120, where it can have a detrimental affect on sealing. Reference is made to a number of embodiments of soft material 130. The embodiments are self explanatory, each of which being configured to provide for good sealing characteristics while exhibiting an unstressed shape that allows space into which the stressed material 120 may flow to avoid flow of that material between the pips 112 and 114 and the casing 120. It is to be appreciated that in some illustrated embodiments the material is a single piece of material (FIGS. 13, 17, 18 and 19) while in other embodiments the material 130 is configured as more than one piece of material (FIGS. 14, 15, 16, and 20). It is further to be appreciated that in FIG. 20, O-rings are illustrated having different cross sectional diameters. O-rings with the same cross sectional diameters can also be used as well as different numbers of O-rings. All of the configurations shown FIGS. 13-20 may have soft material that is molded into a separate ring and placed onto the seal body or molded and bonded directly onto the seal body.
While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
Patent Application
20110148043
