The possibility that Western Massachusetts may hold limited deposits of shale gas is catapulting the contentious issue of hydraulic fracturing, commonly called fracking, into the state.

An industry-supported group plans to hold a daylong session Thursday at the University of Massachusetts Amherst to tell landowners and the public about gas extraction, six months after a federal study mentioned the likelihood of gas deposits in the Pioneer Valley.

While the state probably does not have expansive reserves, American Ground Water Trust executive director Andrew Stone said that small-scale gas development could begin in several years, and landowners need to be given “calm, objective facts.”

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“The facts are, [a study] drew a circle around the middle of Massachusetts” where shale gas could be found, said Stone, whose New Hampshire group includes representatives from engineering and chemical companies on its board.

“We want landowners, individuals, and the community to understand there could be drilling, and they need to be ready for it,” Stone said.

Geologists say it is unlikely the deposits will be extracted anytime soon, because they are probably too small, scattered, and of questionable quality.

No companies have expressed interest in exploring for shale gas, state officials say, and the type of wells needed to get to the gas is prohibited in the state.

Still, a group opposed to fracking has formed through the Pioneer Valley Green-Rainbow Party and the Western Massachusetts chapter of Progressive Democrats of America, with the goal of banning the process.

“We know that it is probably not going to happen in Massachusetts now, but the technology advances so rapidly it is best to take precautions,’’ said Peter Vickery, a lawyer and cochairman of the Pioneer Valley Green-Rainbow Party. He is speaking at the conference to give the Sierra Club’s perspective on fracking.

Hydraulic fracking is a controversial technology that involves injecting pressurized water mixed with chemicals and sand deep into the earth to free large reserves of natural gas trapped in rock.

As its use increases, so have concerns over gas or chemicals seeping into drinking water and groundwater. New York has adopted a fracking moratorium until it develops rules for the process. A 2011 Duke University study found high levels of leaked methane in Pennsylvania wells near shale gas extraction.

In June, a US Geological Survey report assessed five East Coast basins — large geological depressions — and determined they had a total of 3,860 billion cubic feet of natural gas.

By comparison, the gas-rich Marcellus shale formation — marine sedimentary rock that extends through parts of New York, Ohio, West Virginia, and Pennsylvania — could contain 141 trillion cubic feet of gas, according to the US Energy Information Administration. Gas extraction is already taking place in parts of the Marcellus.

Part of Massachusetts is in a geological formation known as the Hartford Basin. The piece of the basin in Massachusetts is 34 miles long and varies in width from three to 15 miles. Springfield is surrounded by it.

The entire basin, which lies under the Connecticut Valley from roughly the Vermont border to the Connecticut shoreline, was one of nine that Geological Survey researchers mentioned but did not fully assess.

The Hartford Basin was formed as the supercontinent Pangea began breaking apart about 220 million years ago. As the Atlantic Ocean began forming in one crack, the Connecticut Valley formed in another, eventually allowing lakes to form.

The waterways would periodically dry up and become wet again, allowing mud and other organic material to layer atop each over time deep in the ground. Those layers today are known as black shale formations, said Richard Little, a geologist and professor emeritus at Greenfield Community College.

Geologists say that unlike the Marcellus shale formation, the Hartford Basin is not likely to be replete with gas. The Hartford’s shale is thin and not in large unbroken planes, meaning it is not ripe for gas extraction, said Stephen Mabee, Massachusetts state geologist. A good portion of the basin was also overheated from volcanic activity, which means any oil or gas is probably gone. Other places weren’t heated enough to produce gas.

“The whole basin has been unevenly cooked,” Mabee said, adding that would make it “difficult to know where the gas is.”

Mabee noted that Texaco did exploratory geophysical work in the 1970s, and then paid for work in the 1980s to examine the hydrothermal history of the Connecticut Valley, but no further exploration took place, he said.

The lead author of the June US Geological Survey study, Robert Milici, said he did not know if there was a lot of gas in the Hartford Basin, and no one will until it is explored.

“I can’t say if there is a lot of gas or little gas,” Milici said. “We really won’t know unless industry becomes interested . . . maybe when gas prices are a bit higher.”

State officials said they would ensure any new energy extraction would not harm the environment.

“We are not aware of any commercially viable deposits in Massachusetts. . . . If there were to be any deposits confirmed in the Commonwealth, we would need to take a close look at their impacts on the environment and public health,’’ said Krista Selmi, spokeswoman for the Massachusetts Executive Office of Energy and Environmental Affairs. “Any effort to perform fracking in Massachusetts would have to be done in a way that does not put our water supplies at risk.”

The American Ground Water Trust says on its website that it “is in favor of developing energy resources, provided water resources are not jeopardized.” Stone said that his nonprofit generates money mostly from registration fees from putting on events and conducted a fracking seminar in North Carolina and is holding one in Texas in March.

Stone said the group does not pay speakers and invites environmentalists to make presentations at conferences. While companies can sponsor the group’s events, Stone said, there are no sponsors for Thursday’s seminar. About 50 people registered for the event.

“We believe this will be educational,” Stone said.

Environmentalists were either surprised to learn of the seminar or expressed doubt fracking would come to Western Massachusetts. Shanna Cleveland, a Conservation Law Foundation attorney, said regulations should be developed only if it is clear fracking could take place in Massachusetts.