US Dow develops first PU used to make proppants for fracking

Focus story by Al Greenwood

GRAPEVINE, Texas (ICIS)–US-based Dow Chemical and Preferred Sands developed a proppant using polyurethane, a first for the resin, executives said during a conference that started on Monday.

Dow’s Teraforce polyurethane is used to coat sand. The result is Preferred Sands’s RCS proppant. It is among the three finalists for an innovation award, given by the Center for the Polyurethanes Industry at its Polyurethanes Technical Conference.

Proppants are used in hydraulic fracturing, the predominant technique used to develop shale gas and tight oil.

The proppants prop up the fractures created by the process, allowing oil and gas to reach the surface.

One type of proppant is made with sand that is encapsulated with phenolic resin.

The product, though, had challenges, said Michael O’Neill, CEO of Preferred Sands. He made his comments on the sidelines of the technical conference.

The phenolic resin would finish curing inside of the well, he said. As a result, it would leach chemicals into the fluids that were also used in hydraulic fracturing.

Once the phenolic-coated sand is injected into the well, it has to be closed within seven hours, O’Neill said. This was becoming a hindrance because wells were becoming larger and requiring more time to develop.

The phenolic-resin-encapsulated sand also tended to slip out of the fractures, O’Neill said. The sand would then clog up the well, while the fractures would collapse. The result lowered the production rate of the well, he said.

“What we needed was something that would be a little more flexible, would hold our product in place so that it wouldn’t flow back but also wouldn’t leach anything out so that fracking would be sustainable,” O’Neill said.

Dow’s solution was to use an entirely new material, replacing a phenolic resin with a polyurethane, said Chris Chrisafides, senior commercial director, North America, Dow Polyurethanes.

The polyurethane offered several advantages, O’Neill said.

It fully cured before being injected inside of the well, so companies would not have a limited time window to use it, he said. Also, the polyurethane did not leach chemicals because it was injected after it was fully cured.

It also cured at a much lower temperature, which cut down on production costs, O’Neill said.

The polyurethane had much more elasticity than the phenolic resin, he said. Essentially, it gripped the fractures better, so it did not slip out and the fractures did not collapse.

While a polyurethane-coated proppant had never been developed, Dow still had much experience encapsulating tiny items with the resin.

Dow AgroSciences has encapsulated herbicides, fungicides and fertilizers with polyurethanes to give the product time-release characteristics, Chrisafides said.

“We felt very fortunate that we had some baseline chemistry and some knowledge around the space,” Chrisafides said. Nonetheless, the company still sought to understand the current technology being used for proppants and technical challenges Preferred Sands was facing.

“We started to come up with a formulation, and we would go and run that formulation in their plant,” he said. “I had people there working around the clock, over the weekend and bringing back feedback.”

In less than six months, the companies had a fully formulated system that was viable and tested in the market, Chrisafides said.

“Today, we’ve developed the product, and we’re down in the wells all over North America. We’re in thousands of wells with hundreds of customers,” O’Neill said.

“And we’re going across the world with it to other countries,” he said. “It works excellent, it leaches no chemicals in the wells, it makes the wells very cost effective, and you get the most production out of it.”

Another finalist for the innovation awards is BASF. It developed Infinergy, the first particle foam that is based on expanded thermoplastic polyurethanes.

Novomer developed Converge, a polyol made from carbon dioxide (CO2).

The Polyurethanes Technical Conference lasts through Wednesday, when the winner of the innovation award will be announced.