The creation of fossil fuels: What's on the Hi-Line

A geologist explained how coal, oil and natural gas are created, and why that means a huge boom of production on the Hi-Line is not likely in the next few years, during a lecture Tuesday in Havre.

Jay Gunderson of the Montana Bureau of Mines and Geology said the geology and geological history of north-central Montana has led to large deposits of coal and natural gas, but access to oil is not so likely.

"The geology here in north-central Montana is not so good for generating oil, " he said during the energy on the Hi-Line lecture series at Montana State University-Northern.

Gunderson said for oil deposits to form, a layer of carbon-bearing rock, with the remains of plants and animals, is trapped under a nonpermeable rock. Heat and pressure convert the remains to oil, which then rises through permeable rock such as sandstone, because it is lighter than water. The petroleum then collects under the trapping layer.

That is what happened in the Bakken formation, where a boom in oil production is happening in northeastern Montana and western North Dakota, and in oil deposits west of Havre closer to the Rocky Mountain Front.

In north-central Montana, the Bakken is present, but is too shallow to produce significant oil that can be economically extracted with current technology, Gunderson said.

Natural gas and coal, however, are greatly present.

Gunderson said the gas is what is known as biogenic gas — rather than being produced by cracking of petroleum, it is created by microbes that produce methane while consuming the biological remains.

Those remains are what is left after a great sea that stretched through the area, from Alaska to the Gulf of Mexico, started drying up.

That also led to the large deposits of coal in north-central Montana. As the plant matter died and collected, it eventually formed peat, which later was converted to coal.