This is Part 3 of a paper written about the projected US Energy profile in the year 2050. In this chapter, we take a look at Natural Gas as an energy source.
The use of natural gas as an energy source is fairly new. In the 1800s, natural gas was used as a fuel for lamps. However, alternative uses were discovered in 1885 by Robert Bunsen upon his invention of the “Bunsen burner”. The Bunsen burner harnessed the power of natural gas for cooking and heating purposes. Though a very helpful fuel, its consumption did not become widespread until the construction of large-scale pipelines after World War II, enabling private residences and businesses alike to use natural gas as a source of heating and cooking power.
Natural gas is seen by many as the ideal transition fuel between traditional fossil fuels, coal and oil, and renewables of the future. With increasing concerns about the environmental and climate change consequences of greenhouse gas emissions, natural gas is heralded as a less harmful energy source.
Natural gas makes up about 22 percent of U.S. energy consumption (EIA AEO 2010). While annual fluctuations in natural gas have ranged from increases to decreases of 6.5 percent, total annual consumption has stayed steady for the past five years, (EIA AEO 2010). However, a rising demand for natural gas is expected in the future. The largest challenge will be ensuring that supply rises to meet demand.
According to the Oil & Gas Journal’s estimates of world proven reserves on Jan 1, 2009 from PennWell Corporation, there is 6,254.364 Tcf left, more than 56 percent of it is in Qatar, Iran, and Russia. However, the United Sates also has a significant amount of natural gas, about 3.8 percent of the world’s proven reserves, (Oil & Gas Journal, 2008). As advances in unconventional shale gas technologies develop, the importance of US reserves will increase tremendously. The timing of the construction of the Alaskan natural gas pipeline is key to projecting U.S. production through 2050. The EIA predicts that the pipeline will be built in 2023, which is a reasonable assumption weighing the risks amid increased demand for natural gas.
The four main types of unconventional natural gas production are coal bed mining, shale gas, tight sands, and gas hydrates. Coal bed natural gas (CBNG), also known as coal bed methane, has grown rapidly over the past fifteen years and now accounts for 12 percent of natural gas production. Coal beds are very rich in methane, and “a cubic foot of coal can contain six or seven times the volume of natural gas that exists in a conventional sandstone reservoir,” (NETL). The DOE has invested in R&D to integrate enhanced gas recovery and carbon sequestration. Carbon dioxide would be pumped into unminable coalmines, storing the CO2, while displacing the methane from the coal. The DOE recognizes the potential of CBNG and has invested in developing this and other technologies further.
Gas hydrates are methane molecules trapped inside deep-water continental shelves found 300 to 500 meters below the seabed. Gas, or methane, hydrates are the most common type of clathrate, a chemical substance which molecules of one material enclose another without chemical bonding. The DOE is working with BP Exploration and Anadarko to produce the first commercially viable gas hydrates by 2015 starting in the Alaskan North Slope. Along with doubts about its economic feasibility, there are huge environmental concerns about the amount of carbon it could contain.
Because of advances in hydraulic fracturing and horizontal drilling as well as the discovery of many more reserves, shale gas has become an increasingly viable source of natural gas production. In addition, the United States has an abundance of shale reservoirs. The Barnett Shale reserve in Texas alone accounts for 6 percent of natural gas production. By 2011, it is expected that most new reserve growth (50 to 60 percent) will come from shale gas. AEO 2010 estimates the recoverable domestic shale gas resources at 347 trillion cubic feet, given the rapid development in recent plays, including Marcellus and Haynesville. The fractures in the shale are vertical, so most engage in horizontal drilling to intersect maximum number of fractures. Some experts are worried about the long-term production rates of horizontal wells. Recent discoveries of recoverable gas in the Marcellus shale in the Appalachian Basin bode well for natural gas production because its location close to the major urban centers of the East will ensure low transportation costs.
Tight gas is similar to shale gas in that it is trapped in unusually impermeable formations, such as impermeable sandstone or limestone.
While the prospect of natural gas vehicles is very attractive, this is not really a feasible solution, due to many economic factors. In particular, natural gas vehicles would involve very expensive and complicated infrastructure to achieve market success. Hybrids and electric vehicles offer the most environmentally friendly future for transportation. The United States should be putting resources into developing the technologies to produce domestic gas and stabilize the natural gas price instead of investing in developing natural gas vehicles.
The availability of adequate storage capacity is also crucial. Estimates of underground working gas storage capacity were 3,889 Bcf in Aug 2009 (EIA AEO 2009). Stored natural gas maintains the reliability of gas supplies during periods of high demand and can help to stabilize prices during periods of low demand, by removing natural gas from the marketplace.