Unlike conventional gas, which typically is found in underground reservoirs composed of sandstone, unconventional gas is found in different types of formations, including coal beds, shale and oil sands. Conventional gas, which often is produced along with oil, has represented the majority of gas production over the past century. But it is maturing and declining, allowing unconventional sources to fill the gap and help expand the resource base. Unconventional natural gas is expected to play an ever increasing role in U.S. gas production in the coming century. Consulting firm ICF International forecasts that production of unconventional gas, including coalbed methane, tight gas and shale gas, will grow from 42 percent of total U.S. natural production in 2007 to 64 percent in 2020.
Coalbed Natural Gas
Coalbed natural gas, or coalbed methane, is now an important component of the supply of natural gas. This gas is stored inside of coal and was once thought to be too dangerous to extract. Recent technology, however, has allowed for safe extraction and has increased supply to meet the growing energy demand. Coalbed methane is found in many places in the world. In the United States, much of the coalbed methane is located in the Rocky Mountain region.
Shale gas is natural gas trapped within shale formations. Shales are fine-grained sedimentary rocks which can have an abundance of natural gas (or petroleum). The ability to tap into North America’s vast shale gas resources has caused a dramatic perception shift about the future of natural gas. Just a decade ago, the United States was looking for ways to import vast quantities of natural gas from abroad to meet its gas demand. Now, the nation is considering exports and is seeking new markets for the clean-burning fuel source. This revolution stems from the ability to produce shale gas using a combination of two proven production techniques -- horizontal drilling and hydraulic fracturing. The combination of these two techniques has allowed shale gas to be extracted economically and has doubled the estimated amount available. Shale gas resources are expected to continue to increase in the future and account for 45 percent of all U.S. natural gas production by 2035. Below is the EIA’s U.S. Natural Gas Supply Projections from 1990 - 2035.
Shale “plays” are shale formations which contain plentiful accumulations of natural gas.
Hydraulic fracturing is the process used to extract natural gas from these shale formations. The technology of hydraulic fracturing has been in use for 60 years in more than a million wells. The process entails injecting water and fracturing fluids under high pressure into a formation to create spaces in the rock pores. These spaces allow natural gas to be freed from under the rock where it was previously trapped. Hydraulic fracturing is an essential component in the ability to develop shale gas, which has helped grow U.S. gas production, creating jobs and economic opportunities.