IntroductionThe U.S. natural gas industry, and by extension the global industry, has witnessed enormous changes over the past decade . During this period, U.S. natural gas production levels increased from a low of 18 Tcf (510 Bm3) in 2005 to a record high of 24 Tcf (680 Bm3) in 2012. At the same time , natural gas prices have fallen to levels not seen since the period immediately following the deregulation of the US gas market in the mid-1990s. The underlying driver of this dynamic has been the very rapid growth in gas production. unconventional natural gas resources, and in particular shale gas resources – historically considered unrecoverable. Technical advances in drilling and reservoir stimulation have been key to unlocking shale gas. . Today's shale gas largely comes from wells drilled with horizontal drilling that have been subjected to large-scale hydraulic fracture stimulation. The combined effectiveness of these technologies in enabling gas production from shale formations (and even other low permeability reservoirs) is such that their development has led to huge upward revisions in the assessed scale of the total recoverable natural gas resource in the United States. Today, analyzes from organizations such as the U.S. Energy Information Administration (EIA) and the Potential Gas Committee (PGC) suggest that potentially recoverable U.S. shale gas resources are in the range of 800 to 1,000 Tcf (23 to 28 Tcm). This contrasts with the National Petroleum Council's (NPC) 2003 assessment, which estimated shale resources at 35 Tcf (1 Tcm). The prospect of a much larger and, indeed, less costly domestic natural gas resource in the United States has major impacts on both. the United States and interns... middle of paper ... the mental processes involved in hydraulic fracturing remain the same. A fluid is injected (water is commonly used) into the wellbore at a rate sufficient to generate a pressure difference between the wellbore and the reservoir. This causes stresses around the wellbore to increase beyond the tensile strength of the rock, in which case it splits or "fractures." Assuming that sufficient pumping rate is maintained, it is possible to "grow" these fractures in both width and length, such that they propagate from the wellbore towards the formation surrounding. Generally speaking, once pumping is complete, the induced fractures close. So, in order to keep the fractures open, proppant material must be placed in the fractures. This is achieved by transporting the proppant to the bottom of the hole as part of the mud comprising the proppant and the fracturing fluid itself..