In a technology development focused on the fracking industry, Dow Chemical and Preferred Sands developed a proppant using polyurethane, a first for the resin, officials said.
Dow’s Teraforce polyurethane ends up used to coat sand and the result is Preferred Sands’ RCS proppant.
Proppants see use 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 consists of sand encapsulated with phenolic resin.
The product, though, had challenges, said Michael O’Neill, chief executive of Preferred Sands. The phenolic resin would finish curing inside of the well, he said. As a result, it would leach chemicals into the fluids also used in hydraulic fracturing.
Once the phenolic-coated sand injects into the well, it has to close 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 injecting 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 injected after it 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.