Shale gas and other hydrocarbons, trapped within massive shale formations, has become an important source of natural gas and oil in the United States since the start of the 21st century and interest has spread to potential gas shales across the rest of the world.
Europe now stands at having an estimated 21 trillion cubic feet, as indicated in the latest environmental impact studies by the US Energy Information Administration (EIA). In 2000, shale gas resources provided less than one percent of total US natural gas production, but by 2010 shale gas accounted for over 20 percent and the EIA predicts that by 2035, 46 percent of the United States’ natural gas supply will come from shale reservoirs. Some analysts expect that shale gas will come to play an expanding role in world energy supply with potential shale gas and shale oil reservoirs. India, Romania, France, Austria, Poland, Ukraine, Saudi Arabia, Russia, and China are but a few countries having large estimated unconventional resources.
Today, low permeability source rock (including shale gas, tight-sand gas, and coal-seam gas) is made economically productive in wells drilled and hydraulically fractured (propagating fractures in the hydrocarbon-trapped rock layers). This fracturing is done by pumping fluids carrying proppant including sand, sintered bauxite, and similar materials and pressurizing the formation until it fractures. The fractures will continue to propagate, typically horizontally, away from the wellbore until the pumping pressure decreases below the fracturing pressure of the formation. The proppant serves to hold the fractured pathways open, creating what is termed “conductivity” for the release of liquid hydrocarbons or natural gas.
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