Seeking to Build a Better Proppant

The movement of a maple leaf as it tumbles gave insight to one of the winners of Statoil ASA and GE Oil & Gas’ first Open Innovation Challenge into the ideal shape for a proppant.

Finding ways to reduce the amount of sand trucked to unconventional oil and gas fields for hydraulic fracturing was the goal behind the recent Open Innovation Challenge

GE and Statoil named Hoowaki and four other companies and institutions winners of the challenge. GE and Statoil recently announced they were taking entries for the second Open Innovation Challenge, a crowdsourcing endeavor that seeks innovative new ideas for treating or recycling water.

The idea behind an X-shaped proppant came from an idea by a Royal Dutch Shell plc official of the conceptual model that governs proppant settling based on “Stokes Law” – referenced in a Society of Petroleum Engineers paper – that drag is a variable that the invention community had not exploited to improve proppant transport, said Ralph Hulseman, company president and co-founder of Hoowaki, in a statement to Rigzone.

Shell made the suggestion to Hoowaki officials after meeting with them in late 2011, thinking that Pendleton, S.C.-based Hoowaki’s expertise in micro-surface design technology might be used to improve proppant. After exchanging proposals throughout the spring of 2012, the companies began working on the product in mid-2012.

Existing approaches have focused on lower particle density or carrier fluid viscosity, said Hulseman.  

“The industry thinking when we started was that ideal proppant particle was a uniformed-size sphere. Proppants need to settle slowly in water, then support a high load in the rock formation crack.”

During the R&D stage, Hoowaki thought about the physics at play at each stage of the use of the proppant particle, then made and tested several different particle designs. Hoowaki’s analysis showed that a sphere wasn’t the optimum shape for any of the stages of use.

“Thus, we needed extensive work to find the optimum shape,” Hulseman explained.

To find that shape, Hoowaki used finite element structural analysis to optimize the ability of the proppant particle to support a load in the crack, and yet have the maximum open void volume.

“Reducing settlement time was harder, as it is difficult to model turbulent tumbling drag flow of a shaped particle,” Hulseman noted. “There was little information available in the scientific literature about how to slow the settling of particles, so we needed to conduct experimentation.”

“We knew that maple leaves both tumble end over end and flutter in broad circles to slow the rate of falling,” Hulseman said. “We tested many shapes until we found the ones that worked best to achieve this effect. The X shape emerged from these studies.”

Before this collaboration, Hoowaki had no experience working on proppants – the company had been focused on medical devices, and automotive and industrial seals.

“Our business is to move tough friction and surface tension problems by designing micro and nano-surfaces to solve these problems,” said Hulseman. “We add those surfaces to extrusion or molding tooling so that our customers can make their improved products and high volume. At the intersection of the physics of surface tension and lubricated friction is fluid drag phenomena.”


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