Hutchinson State geologists have a new theory about how natural gas leaking from a storage cavern found its way underneath Hutchinson. The latest explanation comes after more core drilling along the suspected path.
Ancient tidal channels up to 300 million years old could be the conduit for the natural gas believed responsible for two January explosions in Hutchinson, said Lynn Watney, a geologist with the Kansas Geological Survey in Lawrence.
The core samples also may have dispelled the geologists' first theory. Geologists at first speculated that natural gas leaking from a cavern in Kansas Gas Services Yaggy storage field followed permeable sandstone fingers into Hutchinson.
Watney said Tuesday that another possibility is that gas could be traveling along layers of dolomite found in the core samples. They are at the depth where the gas is moving.
Crews are using drilling machines to withdraw 1-inch-thick samples from the rock near the gas path to Hutchinson.
The city's geology consultant said the dolomite is a "possible conduit."
"They certainly found dolomite and gypsum at the transmission point," said Joe Ratigan, vice president of Sofregaz in Rapid City, S.D. "It could be."
Kansas Gas Service spokesman Conrad Koehler said the core drilling at that site did not hit gas. Koehler said company geologists also will study the core samples but said he was uncertain whether they subscribe to the tidal channel theory offered by the state.
What puzzles the geologists is the apparent narrow band of dolomite underneath the gypsum, about 300 feet down.
The deposits may flow in the same pattern as the bedrock surface under the ancestral Arkansas River, leading to one theory on why the gas could have flowed from Yaggy southeast into Hutchinson.
"The gas flow is preferably going to be along some structural trend," Watney said. "The flow certainly fits the flow of the river." And the conduit for that flow could be the joint between the dolomite and the gypsum, Watney said.
The gypsum beds could be acting as seals trapping the gas in the dolomite layers, Watney said.
Ratigan said that the dolomite discovery could be site-specific and not applicable across the area affected by the leak.