Curtin University researchers have developed a new process to dehydrate subsea gas that could open up gas fields currently deemed unviable.

 

Dr David Parks, Postdoctoral Fellow in Curtin’s Department of Petroleum Engineering, said the new process did not require toxic chemicals.

 

“There’s always water in natural gas, so to prevent blockages in deep subsea pipelines, companies typically inject chemicals such as glycol and methanol into the gas stream,” Dr Parks said.

 

“That costs a lot of money, in chemical costs and the increased complexity of connections from the shore, which means companies generally only exploit fairly large fields.

 

“Our subsea dehydration process can open up projects that are currently too expensive, making stranded fields economical.”

 

Dr Parks said a typical gas pipeline could develop hydrates at temperatures below 12 degrees. These hydrates, a combination of gas and water that form as a crystalline, ice-like material, are potentially disastrous.

 

“Hydrates can block a pipeline, and when that happens, removal can be very difficult and companies may have to abandon it,” Dr Parks said.

 

“Subsea temperatures commonly get down to 4 to 5 degrees, so to avoid hydrates you either keep the pipeline warm, treat the water with chemical additives or remove the water.”

 

The new process has two stages. The first utilises the Joule-Thomson effect in which water-saturated natural gas is expanded and the drop in pressure results in cooling and the expulsion of water. In the second stage, gas is sent to a controlled vessel that creates hydrates.

 

“By encouraging hydrate formation in a controlled environment, those hydrates pull water out even further, leaving gas that can be safely transported,” Dr Parks said.

 

Successful pilot plant testing of the process was undertaken in the Clean Gas Technology Australia Laboratories at Curtin. The next step is testing at field level.

 

“The outcomes of our experiments suggest the technology has significant merits. It saves costs, is small and simple enough for subsea installation and requires minimal maintenance. Now we’re looking at industry to help develop the project further,” Dr Parks said.

 

Dr Parks is also pursuing technology to support this breakthrough, recently receiving a $35,000 industry grant to investigate subsea electrical generation for offshore platforms.