Fossil natural gas developed over millions of years from ancient organic matter trapped in the ground. In the past, most of the natural gas produced in Canada came from gas deposits found in porous rock such as sandstone or limestone. These types of deposits are called conventional because gas is extracted using conventional vertical gas wells. Canada’s largest conventional gas deposits are located in Alberta.
Fossil natural gas is also found in shale deposits and in coal bed seams. These types of gas deposits require different production methods, thus considered to be unconventional deposits. Improvements in technology to extract natural gas from unconventional deposits have dramatically increased estimates of natural gas supply in North America. Production methods include horizontal drilling and multi-stage hydraulic fracturing to release gas from solid rock formations.
The share of natural gas from unconventional deposits in natural gas supply in North America is increasing. In the United States, such natural gas represented 25% of total gas production in 2010. Canadian natural gas production from unconventional deposits is at an earlier stage. Canada’s National Energy Board forecasts that unconventional production will grow at rates similar to those seen in the United States.
Natural gas from both conventional and unconventional deposits are mostly made up of methane, but may also contain other gases and impurities. In both cases, the extracted gas needs to be processed and purified.
Renewable natural gas or biomethane is biogas purified to meet pipeline standards. Renewable natural gas can be used interchangeably with fossil natural gas, but offers the additional advantages of being a near-zero GHG emission renewable source of energy. Raw biogas from waste sources such as landfills, agricultural wastes, and wastewater treatment plants can be upgraded to produce renewable natural gas. This “green” gas can be directly introduced into existing pipeline systems and used, like fossil natural gas, in heating applications, electricity generation, or as a transportation fuel. Renewable natural gas is an emerging opportunity to use local waste resources to produce a near-zero GHG emission fuel.