Visiting Rotary Club speaker Ed Ireland provided an overview of the Barnett Shale and drilling techniques during Wednesday’s meeting.

Ireland, executive director of the Barnett Shale Energy Education Council, said the Fort Worth-area shale is still the largest-producing natural gas field in America, though the Eagle-Ford Shale of South Texas and the Marcellus Shale, still in development in Pennsylvania,, may soon overtake it.

But Ireland said much of the technology oil and natural gas drillers will employ in future endeavors began in the North Texas development.

He also explained advanced drilling technology brought natural gas back from obscurity. Ireland reported that from 1960 to 2002, natural gas supplies were dropping, as virtually all shallow pockets of it had been found and used.

“We went from a declining reserve of natural gas in the U.S. to an increasing one,” Ireland said. “Increasing very quickly. Increasing so much that the price of natural gas has dropped like a rock and it’s still continuing to be developed.”

He said natural gas is the cleanest-burning fuel on hand, and that the renewable technologies of solar panels and wind turbines, even at their best, still require it as a backup.

“The sun doesn’t always shine and the wind doesn’t always blow,” Ireland said. “What are you going to do when you’re in that situation? You can’t depend on wind turbines and solar panels all the time.”

Overview highlights:

• The method of hydraulic fracturing in obtaining natural gas, also known as “fracking,” took 20 years to develop successfully in the Barnett Shale. The local pioneer was George Mitchell, who began experimenting with fracturing methods in 1981. The current process delivers a mixture of water, sand and chemicals at pressures of up to 5,000 pounds per square inch against the shale rock, cracking it open, creating fissures and holding them open with sand as extractable natural gas flows out of them.

• Another developmental boon in the fracturing process has been horizontal drilling, which Ireland said was perfected by Devon Energy in 2002. A drilling bore travels into the shale vertically but then turns horizontally, giving itself better access to more natural gas while fracturing. Ireland said imaging and drilling technologies make it possible for crews to drill a well in a week to 10 days, rather than in several weeks.

• Ireland said a well requires up to 4 million gallons of water, due to fracturing needs. Water comes from either freshwater sources or specially-drilled water wells. But Ireland said a common criticism is that the process appears to be a tremendous water waste.

“It always shocks people,” he said. “It sounds like a lot of water but in the scheme of things, it’s not.” Ireland said he asked representatives of the Tarrant Regional Water District about water usage in oil and gas drilling and was told only 1 percent of their sales — through scattered municipalities — go to that purpose.

“The largest single use of use of water is watering yards,” he said, explaining the Tarrant district makes up to 60 percent of its annual sales of water through the abundance of residential watering. “Why do you suppose the first thing they restrict is outdoor watering?” he said. “That’s because it’s the largest single use.”

• Ireland said the Barnett Shale’s economic benefit has been tough to dispute. In 2010, the Fort Worth Independent School District collected $11 million in ad valorem tax income from the shale facilities. The Fort Worth Chamber of Commerce reported the shale produces up to $11 billion annually in economic activity and has generated more than 100,000 jobs in North Texas.

“It’s a huge economic engine that is helping North Texas,” he said.