Hydrate Management for Hydrate Deposition in Gas-Filled Vertical Pipes

Abstract

Deadlegs are defined as pipe sections in intermittent use for production or special services in oil/gas production systems. Deadlegs often pose hydrate control challenges to gas and oil production systems as the fluid inside is close to stagnant and therefore can be rapidly cooled by the environment without proper insulation or heat tracing. Water vapor can condense in the deadleg, resulting in a potential hydrate risk. Over time the deadleg may be blocked completely by hydrates. The hydrate challenges, if not properly managed, can cause severe consequences in terms of safety and cost for oil/gas productions. A systematic study has been performed to better understand the process and mechanism of hydrate deposition in deadlegs. To study hydrate deposition in deadlegs experimentally, laboratory scale deadleg systems were designed and built to consider pipe sizes of 1-, 2-, 3-, and 4-in. inner diameter and approximately 50 in. long. The pipes were gas-filled and saturated with water from a reservoir at the bottom of the pipe. The experimental work focused on measuring hydrate deposition, and in some cases, plugging, for different water reservoir temperatures (30 to 80 °C), pipe wall temperatures (-10 to 15 °C), and duration (1 to 84 days). The results from measurements provided insights into the dynamic process of hydrate deposition, such as the mechanism for hydrate deposition, plugging, and distribution along the pipe.