MIT innovation means no sticking points for hydrates
June 1, 2017
New chemical barrier formula could help prevent ice adhesion altogether
Chemical barriers which help ketchup slide out of bottles could aid the oil industry with hydrate formation. Methane hydrates, also known as methane clathrates, are slush-like combinations of methane gas and water which form at the low temperatures and high pressures present at many offshore wellheads, and in pipeline infrastructure. This can cause serious issues with flow rates, with more severe blockages leading to pipeline ruptures or expensive shutdowns.
Hydrate formation has also been partly blamed for the failure of the containment dome during the 2010 Deepwater Horizon disaster, when the frozen mixture blocked a vital outlet pipe, preventing it from redirecting the flow of leaking hydrocarbons to a tanker on the surface.
A new paper by researchers at MIT proposes a new solution: an unreactive barrier chemical which prevents their formation altogether. The method was recently described in a paper published in the ACS Applied Materials and Interfaces journal, written by associate professor of mechanical engineering Kripa Varanasi, postdoc Arindam Das, and recent graduates Taylor Farnham and Srinivas Bengaluru Subramanyam. Their research was backed by Eni and awarded through the MIT Energy Initiative.
No ice, thanks Conventional strategies for dealing with hydrate formation include using heated pipelines, depressurisation or the use of chemical additives to break down any solids which have stuck. However, as is often the case with these things, prevention is far better than the cure.
Doing so requires stopping the very first particles of hydrate from adhering to the pipe. “Once they attach, they attract other particles” of hydrate and a plug or deposit will begin to form quickly, Farnham explained in a statement. “We wanted to see how we could minimise the initial adhesion on the pipe walls.”
Their system involves two steps: first the creation of a textured coating on the container wall, and then the addition of a lubricant that gets trapped by the texture and prevents contents from adhering. Coating the inside of the pipe with this material helps create a water-barrier layer along the pipe’s inner surface. This barrier layer can prevent the adhesion of any ice particles or water droplets to the wall and prohibits any build-up of hydrates.
Unlike some chemicals which break down the plugs, this method is passive, and the barrier will not react with either the hydrocarbons or the surface of the pipe. Instead, the oleophilic coating will attract liquid hydrocarbons that are already present in the flowing crude oil, creating a thin surface layer that naturally repels water. “If the oil [in the pipeline] is made to spread more readily on the surface, then it forms a barrier film between the water and the wall,” Varanasi added.
“We are using the liquid that’s in the environment itself,” rather than applying a lubricant to the surface, he continued. Because the key characteristic in hydrate formation is the presence of water, as long as this can be kept away from the pipe wall any build-up can be stopped, and as long as the hydrocarbons cling to the pipe wall, water will be prevented from touching it.
Because hydrates form at extreme temperatures, the team used a proxy chemical – in this case cyclopentane – for their early lab tests. However, they have reported that the test system has performed “very effectively,” with no hydrate adherence.
In the conclusion to their paper, the authors note: “We anticipate that allowing the complete spread of nonaqueous, water-immiscible films on solid surfaces will reduce gas hydrate adhesion, even under high pressure condition; however, further study is warranted.”
The researchers were unavailable for comment on the next steps in their research, however given the seemingly effective results of their innovation, InnovOil imagines industry observers will be quick to take notes.