The ways to harvest natural gas are getting more unconventional

Coal bed methane is an unconventional method of gas recovery

The quest to find and harness the cleanest, safest and most affordable energy sources remains a fluid competition, in which unconventional gas stands as a serious leading contender.

Nuclear energy was enjoying a resurgence in popularity in recent years because of its low emissions levels. That was until an earthquake and subsequent tsunami brought about a crisis at Japan’s Fukushima Daiichi nuclear complex.

In the wake of that incident, governments and energy industry experts are feeling a heightened sensitivity to the risks of nuclear power, and a renewed openness to alternatives. That will likely cast a new light on supplies of unconventional natural gas as a cleaner, safe and abundant energy supply.

Peter Tertzakian, Chief Energy Economist and Managing Director, ARC Financial Corp, has observed the rise in price of natural gas in Japan since the nuclear incident. “The ball is in Canada’s court to take advantage of this opportunity to sell our natural gas to the Asian markets,” he says.

Renewed interest in gas

Although Canada is the world’s third largest producer of natural gas, this relatively clean and safe fuel has taken a back seat recently in drilling and production priorities. But that is beginning to change, as world oil markets react to turmoil in the Middle East, and the nuclear crisis in Japan casts a dark shadow over that energy source.

Enter natural gas, in its various forms:

“Conventional gas” is trapped under pressure in small porous zones within rock, usually sandstone, carbonates or siltstones. It is the easiest gas to extract and has been the staple of the industry for a century.

“Unconventional gas” sources include tight gas, coal bed methane, shale gas and gas hydrates. Each is found in very different formations. In unconventional sources, gas molecules are attached to the carbon molecules by a process called adsorption. The gas adheres to the hydrocarbon material and extraction requires depressurizing the reservoir. Gas also occurs in tiny pores that are poorly connected, making the gas difficult to produce.

“Tight gas” is when the reservoir is in sandstone, similar to conventional gas,” says Kevin Heffernan, Vice-President of the Canadian Society for Unconventional Gas (CSUG). “The difference is in the permeability, the ease with which the gas can flow through the rock. Low permeability is called tight sand. The gas has difficulty moving through the pores between the sand grains and extraction requires hydraulic fracturing.”

Strict guidelines

“If you aren’t taking proper steps in the cementing process, you can have problems,” says Dawson. “But well construction guidelines are strict and if a well is constructed properly, then there should not be migration of gas to the higher levels.”

Hydraulic fracturing has been used in the industry for 60 years and more than one million fracturing operations have occurred in North America, says Heffernan.

Water is necessary in the hydraulic fracturing process and this is of concern to environmentalists and landowners. The water is mixed with chemicals and sent down the well bore under great pressure. Each company has its own mixture of what it sends down the well bore and the formula also depends on the specific rock formation. The wastewater remaining after the gas has been retrieved contains contaminants from the rock formation, such as natural salts, heavy metals and, in places, minor amounts of hydrocarbon.

Another issue is how the water is handled once it is recovered, how spills and leakage are prevented and how the water is treated before it is discharged or reused. In Alberta, the recovered water from hydraulic fracturing cannot be disposed directly to the surface. It has to be treated, recycled or made safe to discharge.

“The major issues are the volume of water required, which affects the water table, and proper handling and disposal of waste water,” says Severson-Baker. In addition, a lot of energy is required in the actual process of hydraulic fracturing, and like conventional gas, shale gas can have very different C02 concentrations in different reservoirs and different places.

Coal bed methane

“Coal bed methane” is natural gas obtained by releasing the pressure on the coal so the methane that has been “adsorbed” to the coal molecules can escape. The methane is “desorbed” from the coal to travel to the wellbore and into the pipeline. If there is water in the coal seams, it is considered a “wet reservoir” and water is removed from the rock in order to obtain the gas. Alberta’s large Horseshoe Canyon formation has coal seams considered to be dry gas because the fractures contain methane rather than water.

Meanwhile, swirling in the industry’s crystal ball is an undeveloped resource known as “gas hydrates.”

“In gas hydrates, the gas is solid,” says Dawson. “Under unique temperature and pressure conditions, methane will change from a gas to a solid. In the Arctic permafrost, the gas has changed into a solid and is bound up with water. If you drill and change the pressure and temperature, you can create the conditions to turn the solid back into a gas.”

“There is an estimated 28,000 trillion cubic feet of hydrates which represents an enormous potential resource,” says Dawson.

 

Commercial development of gas hydrates will have to wait until the technology has been developed to extract them. There are a few geological organizations looking at developing the process, and currently, on the north slope of Alaska, Conoco and BP are planning a pilot project to develop gas hydrates.

 

By Richelle Wiseman

 

Troy Media

 

 

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