HPHT environments combine temperatures exceeding 177°C (350°F) and pressures above 15,000 psi, common in deepwater subsea wells. Seals must resist extrusion, chemical attack from H2S, CO2, and amines, while surviving multiple RGD events. Only qualified materials passing 10-cycle decompression tests at extreme conditions are accepted by major operators https://globalsealstech.com/product/rgd-rapid-gas-decompression-o-rings/