As a result of new regulations, exploration and production companies engaged in drilling activity in Montana are required to disclose the majority of chemicals they use for hydraulic fracturing or "fracking." These written disclosures need to be completed for every well drilled in Montana and then provided to the state, according to The Billings Gazette.

Fracking is a process that entails a liquid mixture of various chemicals and sand being shot down a well to fracture existing shale formations, the media outlet reports. Fracking is utilized in horizontal drilling and involves injecting approximately 1 million gallons of liquid per well at high pressure, which breaks up the shale, releasing oil and gas deposits.

Companies have resisted efforts to necessitate this disclosure, stating that the chemicals used are trade secrets, The Associated Press. Two federal agencies have mandated standards that allow these companies to avoid revealing certain chemicals if it means revealing trade secrets, according to The Billings Gazette.

Fracking has become a hot-button issue as domestic production has picked up significantly in the last few years. One of the largest plays is the Bakken formation, which the U.S. Geological Survey estimates as having between 3.0 to 4.3 billion barrels of oil.