A team of researchers at MIT has developed a coating that could stop the buildup of hydrate ices that slow or block oil and gas flow. These hydrates are potentially explosive and are largely responsible for the initial failure to contain the Deepwater Horizon oil spill that rocked the Gulf of Mexico in 2010.
The coating may also prevent blockages inside oil and gas pipelines that can lead to expensive shutdowns to clear a pipe, or worse, to pipeline rupture from a buildup of pressure.
The new method of preventing the icy buildup is described in a paper in the journal ACS Applied Materials and Interfaces. The key to the new system is coating the inside of the pipe with a layer of a material that promotes spreading of a water-barrier layer along the pipe’s inner surface. This barrier layer, the team found, can effectively prevent the adhesion of any ice particles or water droplets to the wall and thus thwart the buildup of clathrates that could slow or block the flow.
Unlike previous methods, such as heating of the pipe walls, depressurization, or using chemical additives, which can be expensive and potentially polluting, the new method is completely passive—once in place it requires no further addition of energy or material. The coated surface attracts liquid hydrocarbons that are already present in the flowing petroleum, creating a thin surface layer that naturally repels water. This prevents the ices from ever attaching to the wall in the first place.
Existing prevention measures, known as flow assurance measures, “are expensive or environmentally unfriendly,” says associate professor of mechanical engineering Kripa Varanasi, and currently the use of those measures “runs into the hundreds of millions of dollars” every year. Without those measures, hydrates can build up so that they reduce the flow rate, which can reduce revenues, and if they create blockages then that “can lead to catastrophic failure,” Varanasi says. “It’s a major problem for the industry, for both safety and reliability.”
The problem could become even greater, says postdoc Arindam Das, the paper’s lead author, because methane hydrates themselves, which are abundant in many locations such as continental shelves, are seen as a huge new potential fuel source, if methods can be devised to extract them.
Such deposits would be even more vulnerable to freezing and plug formation than existing oil and gas wells. Preventing these icy buildups depends critically on stopping the very first particles of clathrate from adhering to the pipe.
The key characteristic in clathrate formation is the presence of water, so as long as the water can be kept away from the pipe wall, clathrate buildup can be stopped. And the liquid hydrocarbons present in the petroleum, as long as they cling to the wall thanks to a chemical affinity of the surface coating, can effectively keep that water away.
The research was funded by the Italian energy company Eni S.p.A. through the MIT Energy Initiative.
Arindam Das, Taylor A. Farnham, Srinivas Bengaluru Subramanyam, and Kripa K. Varanasi (2017) “Designing Ultra-Low Hydrate Adhesion Surfaces by Interfacial Spreading of Water-Immiscible Barrier Films” ACS Applied Materials & Interfaces doi: 10.1021/acsami.7b00223