Operational Improvements in Sour TEG Dehydration Units

One of the largest sour oil and gas processing stations in the south of Oman, operated by Petroleum Development Oman (PDO), was commissioned in mid-2019. The facility employs two triethylene glycol (TEG) dehydration units designed to reduce the water content in natural gas to required levels before it is injected back into the field for enhanced oil recovery. However, shortly after the plant became operational, both TEG units began to experience major operational challenges. These included high total suspended solids (TSS), low glycol pH, and excessive TEG losses. These problems led to frequent process disruptions, increased downtime, and raised significant health, safety, and environmental (HSE) concerns. This study aims to systematically identify and assess the recurring performance issues in the TEG systems. A comprehensive root-cause analysis was conducted, followed by evaluation of practical and technically sound remediation measures. The study follows good engineering practices, with specific alignment to Shell's Glycol Type Gas Dehydration Design Engineering Practices (DEP), in addition to special considerations for sour service applications. Key findings highlight the corrosive nature of acid gases such as hydrogen sulfide (H2S) and carbon dioxide (CO2) dissolving into the glycol, which accelerated internal corrosion of carbon steel components. Additionally, it was observed that the flash vessel design was inadequate, allowing hydrocarbon-rich glycol to reach the contactor and negatively impact its performance. Further root causes included poor filtration upstream of the contactor, which permitted solids to accumulate, and process instability triggered by suboptimal pigging procedures and control valve behavior. Several base recommendations were developed, tested, and successfully implemented on the dehydration units. These included switching to sodium acetate buffering to maintain a more neutral and stable glycol pH, upgrading the flash vessel internals with adjustable weirs and hydrocarbon skimmers, relocating the glycol make-up point to the flash drum to reduce contamination, installing cartridge filters at the TEG inlet scrubber to improve filtration efficiency, and enhancing process control through better flow regulation and pigging velocity limits.