Natural gas production in Butler County has increased each year since 2011, when unconventional wells produced more than 11.6 billion cubic feet. Last year the Butler County wells produced more than 170 billion cubic feet, according to the state Department of Environmental Protection — more than 3 percent of the state's total gas production.

Pennsylvania has been named the nation's second-largest producer of natural gas for the fourth year in a row, according to a report issued last week by the U.S. Energy Information Administration.

The group, which monitors energy production and consumption statistics across the country, said Pennsylvania produced nearly 5.1 trillion cubic feet of natural gas in 2016, nearly all of it from unconventional wells tapping into the Marcellus Formation.

Pennsylvania is second only to Texas in terms of natural gas production — and Butler County is playing a big part. The county is one of the region's leaders in natural gas production, according to online information kept by the state's Department of Environmental Protection.

For 2016, the department reported, unconventional natural gas wells in Butler County produced more than 170 billion cubic feet of natural gas — 3.34 percent of the 5.1 trillion cubic feet produced by unconventional gas wells across the state.

That's the third-most of any county in Western Pennsylvania, according to the DEP. Only Washington (838.9 billion cubic feet) and Greene (693.8 billion cubic feet) produced more natural gas with unconventional wells last year. Those two counties produced more than 30 percent of the state's natural gas in 2016.

According to state data Butler County's unconventional well production has increased every year since 2011, the first full year DEP began breaking out unconventional well production from its annual oil and gas reports.

The rise — from just 11.6 billion cubic feet that year to nearly 15 times that amount last year — mirrors a statewide increase in natural gas production that has kept Pennsylvania at the forefront of the nation's shale drilling rush despite a downturn in drilling activity that began in 2015. The EIA reported that natural gas supplied nearly 33 percent of Pennsylvania's electricity last year — a dramatic uptick from 2007, when it accounted for just 8 percent.

But as use and production have skyrocketed, a growing supply of the commodity has caused prices to plummet from more than $10 per thousand cubic foot (Mcf) in 2008 to an average of $2.50 per Mcf last year. The drop in prices prompted many drilling companies to roll back investments in exploratory drilling and production wells.

Last year there were 31 unconventional wells drilled in Butler County, according to the DEP, down from 85 in 2015. So far this year 19 unconventional wells have been drilled and 42 permits issued, according to DEP data.

Despite the downturn, observers say there might be signs that drillers are beginning to ramp up operations again. As of last week oil and gas drillers had 34 drilling rigs in Pennsylvania according to Baker Hughes, an oil field services company owned by GE which publishes weekly tallies of rig locations.

That's the highest number of rigs to be based in Pennsylvania since 2014, when the company said the state hosted an average of 42 drilling rigs per week, and more than double the number of drilling rigs that were in the state at this time last year.

Dave Spigelmyer, president of the Pittsburgh-based Marcellus Shale Coalition, an industry advocacy group, said he was “cautiously optimistic” about forecasts predicting more investment from drillers going forward. But, Spigelmyer added, the companies “continue to face challenging market conditions as well as stiff competition from other shale states.”