Production packers employ Downhole Seal Stacks to isolate annuli, with swellable elastomers expanding in hydrocarbons for permanent barriers. HNBR swells 200% in oil, sealing rough casings. Challenges: uneven swelling, addressed by zoned designs. Halliburton systems achieve V0 rating per API 11D1. In shale, they boost EUR by 15%. https://globalsealstech.com/media/