A judge heard arguments Tuesday over whether Wyoming regulators should empower the public to look up the ingredients in the chemical products used for hydraulic fracturing, the petroleum industry practice that splits open oil and gas deposits with pressurized water.

The Powder River Basin Resource Council and others say landowners need to know what those chemicals are in case a gas or oil well rupture or some other mishap released pollutants into their well water. The council sued last year after the Wyoming Oil and Gas Conservation Commission partially denied its request for lists of ingredients in fracking chemicals.

Landowners who don't know which chemicals are used in the fracking process are unable to test their groundwater for those specific substances before any contamination occurs. If pollution were to occur, the companies responsible could plausibly deny they were the ones who caused the problem, attorney Tim Preso argued for the council.

"It's a black box. That's the reason why so many landowners are concerned," Preso told Natrona County District Judge Catherine Wilking.

Attorneys for the commission and the Houston-based oilfield services company Halliburton argued that the ingredients often are closely guarded trade secrets that can be cloaked from public release under Wyoming's open records law. Public disclosure, they argued, could enable a company's competitors to reverse-engineer their best fracking chemical formulations.

That could discourage companies from using their newest products in Wyoming, they said.

"Hopefully the new products are going to be more cost effective, or ecologically more benign," assistant attorney general Eric Easton said. "Innovation is a key part of all of this."

The state seeks dismissal of the lawsuit. Wilking said she would rule within two months.

Fracking involves pumping water and sand underground to split open oil- and gas-bearing formations. The water mixture includes a proportionately small amount of chemicals that help the fine sand flow into the newly created fissures and keep them propped open.

In 2010, Wyoming became one of the first states to require companies to tell its Oil and Gas Conservation Commission regulators the ingredients in the fracking chemical products they use. Environmentalists praised the new rules, but companies soon began to seek trade secret exemptions that prevent public disclosure of the constituent ingredients.

Commission staff often rubber-stamped the trade secret requests with little regard to whether they were justified on consistent grounds, Preso argued.

"Clearly there are some important proprietary interests. We're not saying there are not," he said.

The commission staff needs to make certain, however, that companies have provided enough specific information to justify withholding the ingredients from the public, he said.

Wilking asked Easton how landowners should conduct baseline contamination tests when they don't know which specific chemicals to test for in their groundwater. Easton said it was a "tough question" but a landowner could order a generic test of contaminants.

"You could run a priority pollutants screen," agreed Steven Leifer, a Halliburton attorney who argued on the state's side. "If somebody wants to test for hazardous substances, they could certainly do it."

Leifer described his own pancake recipe to show why ingredient disclosure could be a problem for companies like Halliburton. The recipe includes vanilla flavoring, he said, and anybody who can make pancakes should recognize that's the special ingredient.

Except nobody knows how much vanilla is used, Preso said on rebuttal. Preso suggested Leifer might use a teaspoon of vanilla while he used a quarter of a cup with awful results.

"Just knowing he used vanilla doesn't allow me to make the classic Leifer recipe," Preso said.

Likewise, he said, the Powder River Basin Resource Council is looking for ingredient lists, not the formulas or recipes that could be used to re-create fracking chemical products.