In this study we subjected high density polyethylene (HDPE) and polyamide-11 (PA-I l) to multiple rapid decompressions in a crude oil environment with high pressure methane/carbon dioxide and mixtures of methane, carbon dioxide, and hydrogen sulfide at typical use
temperatures, then measured the effect of the decompressions on the mechanical properties of the materials. We observed that the HDPE was severely damaged after the first decompression from 10,000 psi (69 MPa) at 1000 psi (6.9 MPa)/min with methane/CO2 as the pressurization gas. The PA- 11 did not suffer any significant loss of mechanical properties after 20 cycles in any of the gas environments.