FUNCTIONALLY GRADIENT ELASTOMER MATERIAL FOR DOWNHOLE SEALING ELEMENT

A sealing device of enhanced configuration for use in downhole in a well. The device may include an element of elastomeric and unitary construction. At the same time, however, the element may include a substantially cured outer shell disposed about a substantially under-cured inner core. Thus, enhanced robustness and durability may be provided to the device in light of downhole conditions without sacrifice to sealable function of the device.

DETAILED DESCRIPTION

Embodiments herein are described with reference to certain types of downhole sealing devices. For example, conventional packers are shown for zonal isolation in a well. However, more unique types of packers and a host of other sealing devices may take advantage of embodiments of functionally gradient elastomer materials as detailed herein. Regardless, the sealing device may include an element utilizing an elastomer with a substantially cured outer shell about a substantially under-cured inner core.

Referring now toFIG. 1, side and enlarged sectional views of an embodiment of a functionally gradient material sealing element are shown. In this embodiment, the sealing element is incorporated into a downhole isolation packer disposed about a tubular. The downhole sealing element in a borehole annulus includes an elastomeric material (e.g. a rubber) molded in ring shape and installed into the metal mandrel. The element can energize and/or swell when an activating system (mechanical loads or fluids) is in place. Conventional sealing element is made from homogeneously mixed polymer compounds and then cured to a uniform part. The present invention relates, in general, to a seal element that were intentionally made with non-uniformly distributed property to achieve better sealing performance by minimizing seal failures associated with extrusion, temperature cycles, and degradation.

The Packer sealing element consists of 1 to 3 pieces of elastomeric rings installed in a metal mandrel. When activated, the elements provide a seal in annulus space between the mandrel and casing. Once sealed, the elements undergo pressure differential from both above and below the seal, as well as temperature cycles due to downhole temperature and fluid injection from surface.

In the case when packer element is energized by mechanical force pushing the gage ring, hyper-elastic strain energy is stored in the packing elements due to large compressive deformation within the elements. This stored strain energy results in contact pressure at the sealing surfaces (casing ID and mandrel OD) thus provides seals. In a defined setting load case, the lower modulus (softer) element generates more stored elastic energy. When temperature decrease occurs due to fluid injection, the decrease of contact force is proportional to the modulus of element (G), the coefficient of thermal expansion (α), and the temperature drop (ΔT) as was stated in the following expression:

Therefore, a softer elastomer compound is favored by maintaining a better seal with less loss in sealing force when cooling down. However, most of the downhole seal failure attributes to extrusion of the sealing elements under differential pressure. Higher modulus material generally provides better extrusion resistance. So to combine those two requirements, a functionally gradient elastomer material (FGEM) is presented in this invention where a softer inner core is embedded in the harder outer shell. The modulus differential can be achieved by adjusting curing characteristic of the part during molding process.

FIG. 1illustrates the design of the FGEM material in a downhole packer element. The harder shell is mainly for extrusion resistant purpose and the overall softer material will help with sealing capability. Tests were performed using side-by-side comparison between homogeneous material and FGEM in system level.

With added reference toFIG. 2a chart summarizing modulus data for the material ofFIG. 1upon exposure to varying temperatures is depicted. More specifically,FIG. 2shows the FGEM element being used for the test. Test follows ISO 14310 V3 standard and the pressure holding results for the two element systems are summarized in the following two tables. The FGEM elements exhibit better differential pressure capability, especially when a larger ΔT is present. Due to the nature of this particular FGEM element design with soft inner core extends to element ID, excessive amount of rubber was extruded from the OD of mandrel.

In addition to the uses noted hereinabove, the embodiments of the seal element material construction detailed hereinabove may be utilized in any bottom hole assembly where packers and/or seals may be employed. The sealing element of the present invention maybe O-ring seals, T-seals, V-seals, and packing elements for cased hole packers, open hole packers, and swell packers. The polymer material may comprise elastomer such as NBR, HNBR, EPDM, FEPM, FKM, FFKM. The seal element may further include a reinforcement material such as a powder material, a fiber material, or nanoparticles with scale range from 1 nanometer to approximately 500 nanometers. Depend on application, the property/functionality in the FGEM that varies spatially may include modulus, hardness, strength, elongation, volume swell, degradation temperature. The gradient of those properties can also be in all directions (radial, angular, and axial).

With specific reference to the alternate embodiments ofFIGS. 3-8,FIG. 3depicts a side view of an alternate embodiment of the material employed in an O-ring seal configuration. Meanwhile,FIG. 4depicts an alternate embodiment of the material employed in a T-seal configuration. Similarly,FIG. 5is an alternate embodiment of the material employed in a V-seal configuration.

Continuing with added reference toFIGS. 6-8, packer embodiments are depicted. Specifically,FIG. 6depicts an alternate embodiment of the material employed as cased hole hydraulic packer elements. Alternatively,FIG. 7is an embodiment of the material employed as open hole hydraulic packer elements whereasFIG. 8is an embodiment of the material employed as open hole hydraulic packer elements.

Embodiments detailed hereinabove provide elastomeric material seals and construction configured for enhanced sealing capability in conjunction with extended life even upon exposure to extreme and/or harsh downhole environmental conditions. The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.