PEFTEC 2017 - Abstract

Abstract Title: The Determination of Oxygen in Hydrocarbon Gas
Abstract Type: Poster
Session Choice: Other
Presenter Name: Mr Matt Kirby
Co-authors:Mr Matt Bower
Company/Organisation: Qa3 Limited
Country: United Kingdom

Abstract Information :

In the oil and gas industry, reservoirs that undergo chemical treatments such as artificial water lifts and hydrate suppression are at risk of introducing oxygen into the process system as the chemicals (particularly methanol) involved often contain dissolved oxygen. The presence of oxygen is undesirable as it promotes several corrosion mechanisms in both sweet and sour reservoirs as well as the potential for the degradation of process chemicals such as MDEA amines resulting in unwanted by-products in the process system.

As a consequence of the issues arising from the presence of oxygen, even at trace concentrations, it is common to find oxygen specification as low as 7.5 µL/L (ppm v/v) imposed on pipelines and feedstocks to gas plants, refineries and petrochemical plants. The sampling of gases for subsequent trace oxygen determination is not straightforward. Whilst in theory the quantification of oxygen at single 1 µL/L concentrations should be possible, in practice accurate, on-site measurements below 100 ppm v/v are rarely achievable due to system leaks and ingress of atmospheric oxygen (21% v/v) into the system.

It is therefore essential that the determination of trace oxygen in gas is carried out at-line (offshore or onshore gas processing facility). Qa3 have developed a sampling apparatus and analysis regimen designed to
(i) prevent contamination from atmosphere oxygen
(ii) reduce equilibrium time and
(iii) achieve an LOQ for O2 that is commensurate with the specifications imposed by many pipeline operators, which are typically ~10 µL/L.