Se Ling High Pressures under Sour Conditions

Sealing high pressure gases with elastomers is a problem as elastomers are essentially a supercondensed gas. The primary interactions (type of gas, heat, pressure) and secondary interactions (water, inhibitors, etc.) that lead to seal failures are reviewed and discussed. The high pressure raises the gas density, and this causes the gases to have extraordinary solvent power (2,3,4,5). The totally dissimilar chemical and molecular aspects of the three gases create a "mixed solvent system" which is very difficult to seal. Secondary Environment The inevitable presence of water makes the C02 and H2S very acidic and therefore necessitates large scale use of inhibitors to prevent corrosion. Oil soluble (film forming) amines create a persistent liquid hydrocarbon environment that can cause pronounced permanent swelling of various elastomers. Low molecular weight alcohols may also be injected to prevent freezing (clathrates). Equilibrium shifts of pressure or temperature can subject the seals to potential explosive decompression. These primary or secondary environments or their combination can lead to seal failure through physical change or time-dependent chemical modification. The various potential failure mechanisms are briefly reviewed below, on the basis of relatively limited knowledge.