Temperature ratings for packer elements define their operational limits in downhole environments where geothermal gradients increase temperature with depth. Shallow wells may operate at 150°F to 200°F allowing standard nitrile elements. Intermediate depth wells reaching 250°F to 350°F require HNBR or low-temperature FKM compounds. Deep wells and geothermal applications exceeding 400°F... https://globalsealstech.com/product/packer-element/