| 摘要 |
A downhole seal (10) comprises a swelling portion (16). The swelling portion (16) comprises a central region (18) comprising a first swelling material and a first end region (20) comprising a second swelling material. The first and second swelling materials have different swelling properties and define portions of the outer surface of the swelling portion. In use, the first and second swelling materials may be specifically selected to achieve a predetermined or preferential swelling characteristic of the sealing portion and thus of the downhole seal, and in particular a preferential swelling characteristic of an end region of the swelling portion and downhole seal.
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