Natural Gas & The Low-Carbon Economy Major US Shale Gas Resources & Existing Pipeline Infrastructure


Source: Navigant Consulting


and energy security concerns that have surrounded it during the last few decades. Unconventional gas is found in low-porosity sedimentary


rock formations that act as both sources and reservoirs for hydrocarbon deposits. Because of their low porosity, gas is more difficult to extract from unconventional formations than from conventional gas reservoirs, which generally contain stores of hydrocarbons that originated in other formations. But as conventional resources have been exhausted, the industry has turned its attention to new sources of gas that were previously dismissed as too difficult and expensive to extract. In the 1970s, gas producers began to develop tight sands that they had discovered in the course of exploration for conventional gas. Using hydraulic fracturing and horizontal drilling, they were able to recover gas from these resources economically, largely in the Rocky Mountain states. Since then, tight sands have grown to account for more than 30% of all gas production in the US. Natural gas is also found in coal seams, where it can pose


serious health and safety risks to coal miners and can, if leaked to the atmosphere, contribute to climate change. Methane is adsorbed onto the pores of the coal, which has very low porosity. This methane, which would otherwise leak into the atmosphere over time, can be extracted economically by drilling into the coal seam. Coal bed methane development, most of it at relatively shallow depths, has been expanding since 1989, starting in Alabama, New Mexico, and Colorado, and later in Utah, Virginia, and Wyoming. Total US production of coal bed methane reached almost 2 trillion cubic feet in 2008 – 10% of total US gas production.


worldPower 2010 In the past few years, the focus of the gas industry has turned


to a third unconventional source: deep shale formations, or non-porous sedimentary rock that mostly lies thousands of feet underground. Starting in the 1990s, independent gas producers began to develop a technique, known as hydraulic fracturing, for injecting high-pressure water into these deep formations, allowing the gas to be released and brought to the surface. First deployed on a large scale in Texas’s Barnett Shale, the technique has subsequently been adapted to a range of shales in other parts of the country, each of which has its own geological distinctions. When natural gas prices shot upward after 2005, the shale ‘gold rush; was on. The largest gas-bearing shale formation, the Marcellus Shale, extends across five states from West Virginia to New York, and is attracting great attention in the northeastern region where energy prices are high and most gas is imported from over 1,000 miles away (Map 1). While shale rock does not give up its methane easily, this


is more than balanced by its abundance. The Potential Gas Committee, an independent authority on gas supplies based at the Colorado School of Mines, estimated potential US natural gas resources in 2008 to be 1,836 tcf, up 39% from 2006 – with the difference due mainly to a steep increase in estimates of recoverable shale gas. Proven reserves have increased 13% to 238 tcf, bringing total gas resources to 2,074 tcf. Assessments by ICF International, the US Energy Information Administration (EIA), and Navigant Consulting Inc. confirm the magnitude of this resource. These figures suggest that US supplies of natural gas could last for 90 years at current rates of consumption. And some experts expect the resource estimates to continue rising as


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