What Triggered the U.S. Shale Gas Revolution?
The use of horizontal drilling in conjunction with
hydraulic fracturing has greatly expanded the ability of
producers to profitably produce natural gas from low permeability geologic formations, particularly
shale formations. Application of fracturing techniques to
stimulate oil and gas production began to
grow rapidly in the 1950s, although experimentation dates back to the 19th century.
Starting in the mid-
1970s, a partnership of private operators, the U.S. Department of Energy and the Gas Research
Institute endeavored to develop technologies for the commercial production of natural gas from
the relatively shallow Devonian (Huron) shale in the Eastern United States. This partnership helped
foster technologies that eventually became crucial to producing natural gas from shale rock, including
horizontal wells, multi-stage fracturing, and slick-water fracturing. 
Horizontal Drilling Technology
Practical application of horizontal
drilling to oil production began in the early 1980s, by which time the advent of improved downhole
drilling motors and the invention of other necessary supporting equipment, materials, and technologies,
particularly downhole telemetry equipment, had brought some applications within the realm of
commercial viability. 
The Work of Mitchell Energy and Development
The advent of large-scale shale gas production did not occur until Mitchell Energy and Development
Corporation experimented during the 1980s and 1990s to make deep shale gas production a commercial
reality in the Barnett Shale in North-Central Texas. As the success of Mitchell Energy and Development
became apparent, other companies aggressively entered this play so that by 2005, the Barnett Shale
alone was producing almost half a trillion cubic feet per year of natural gas. As natural gas producers
gained confidence in the ability to profitably produce natural gas in the Barnett Shale and confirmation
of this ability was provided by the results from the Fayetteville Shale in North Arkansas, they began
pursuing other shale formations, including the Haynesville, Marcellus, Woodford, Eagle Ford and other
The Natural Gas "Game Changer"
The development of shale gas plays has become a "game changer" for the U.S. natural gas market. The
proliferation of activity into new shale plays has increased shale gas production in the United States
from 0.39 trillion cubic feet in 2000 to 4.87 trillion cubic feet in 2010, or 23 percent of U.S. dry gas
production. Shale gas reserves have increased to about 60.6 trillion cubic feet by year-end 2009, when
they comprised about 21 percent of overall U.S. natural gas reserves, now at the highest level since
The growing importance of U.S. shale gas resources is also reflected in EIA's Annual Energy Outlook 2011
(AEO2011) energy projections, with technically recoverable U.S. shale gas resources now estimated at
862 trillion cubic feet. Given a total natural gas resource base of 2,543 trillion cubic feet in the AEO2011
Reference case, shale gas resources constitute 34 percent of the domestic natural gas resource base
represented in the AEO2011 projections and 50 percent of lower 48 onshore resources. As a result,
shale gas is the largest contributor to the projected growth in production, and by 2035 shale gas
production accounts for 46 percent of U.S. natural gas production.
Diffusion of Shale Gas Technologies
The successful investment of capital and diffusion of shale gas technologies has continued into Canadian
shales as well. In response, several other countries have expressed interest in developing their own
nascent shale gas resource base, which has lead to questions regarding the broader implications of shale
gas for international natural gas markets. The U.S. Energy Information Administration (EIA) has received
and responded to numerous requests over the past three years for information and analysis regarding
domestic and international shale gas. EIA's previous work on the topic has begun to identify the
importance of shale gas on the outlook for natural gas.  It appears evident from the significant
investments in preliminary leasing activity in many parts of the world that there is significant
international potential for shale gas that could play an increasingly important role in global natural gas
To gain a better understanding of the potential of international shale gas resources, EIA commissioned
an external consultant, Advanced Resources International, Inc. (ARI), to develop an initial set of shale
gas resource assessments. This paper briefly describes key results, the report scope and methodology
and discusses the key assumptions that underlie the results. The full consultant report prepared for EIA
is in Attachment A. EIA anticipates using this work to inform other analysis and projections, and to
provide a starting point for additional work on this and related topics.
Shale Gas in Worldwide Basins
In total, the report assessed 48 shale gas basins in 32 countries, containing almost 70 shale gas
formations. These assessments cover the most prospective shale gas resources in a select group of
countries that demonstrate some level of relatively near-term promise and for basins that have a
sufficient amount of geologic data for resource analysis. The map at the top of this page shows the location of these basins and
the regions analyzed. The map legend indicates four different colors on the world map that correspond
to the geographic scope of this initial assessment:
Technically Recoverable Shale Gas Resources by Country
|Reserves are in trillions of cubic feet .
Red colored areas represent the location of assessed shale gas basins for which estimates of the
'risked' gas-in-place and technically recoverable resources were provided.
Yellow colored area represents the location of shale gas basins that were reviewed, but for which
estimates were not provided, mainly due to the lack of data necessary to conduct the assessment.
White colored countries are those for which at least one shale gas basin was considered for this
Gray colored countries are those for which no shale gas basins were considered for this report.
The International Shale Gas Resource Base
Although the shale gas resource estimates will likely change over time as additional information becomes
available, the report shows that the international shale gas resource base is vast. The initial
estimate of technically recoverable shale gas resources in the 32 countries examined is 5,760 trillion
cubic feet, as shown in Table 1. Adding the U.S. estimate of the shale gas technically recoverable
resources of 862 trillion cubic feet results in a total shale resource base estimate of 6,622 trillion cubic
feet for the United States and the other 32 countries assessed.
To put this shale gas resource estimate
in some perspective, world proven reserves  of natural gas as of January 1, 2010 are about 6,609 trillion
cubic feet,  and world technically recoverable gas resources are roughly 16,000 trillion cubic feet, 
largely excluding shale gas. Thus, adding the identified shale gas resources to other gas resources
increases total world technically recoverable gas resources by over 40 percent to 22,600 trillion cubic
Conservative Basin Estimates
The estimates of technically recoverable shale gas resources for the 32 countries outside of the United
States represents a moderately conservative 'risked' resource for the basins reviewed. These estimates
are uncertain given the relatively sparse data that currently exist and the approach the consultant has
employed would likely result in a higher estimate once better information is available. The methodology
is outlined below and described in more detail within the attached report, and is not directly
comparable to more detailed resource assessments that result in a probabilistic range of the technically
recoverable resource. At the current time, there are efforts underway to develop more detailed shale
gas resource assessments by the countries themselves, with many of these assessments being assisted
by a number of U.S. federal agencies under the auspices of the Global Shale Gas Initiative (GSGI) which
was launched in April 2010. 
Highly Dependent Countries
Delving deeper into the results at a country level, there are two country groupings that emerge where
shale gas development may appear most attractive. The first group consists of countries that are
currently highly dependent upon natural gas imports, have at least some gas production infrastructure,
and their estimated shale gas resources are substantial relative to their current gas consumption. For
these countries, shale gas development could significantly alter their future gas balance, which may
motivate development. Examples of countries in this group include France, Poland, Turkey, Ukraine,
South Africa, Morocco, and Chile. In addition, South Africa's shale gas resource endowment is
interesting as it may be attractive for use of that natural gas as a feedstock to their existing gas-to-liquids
(GTL) and coal-to-liquids (CTL) plants.
Countries with a Natural Gas Infrastructure
The second group consists of those countries where the shale gas resource estimate is large (e.g., above
200 trillion cubic feet) and there already exists a significant natural gas production infrastructure for
internal use or for export. In addition to the United States, notable examples of this group include
Canada, Mexico, China, Australia, Libya, Algeria, Argentina, and Brazil. Existing infrastructure would aide
in the timely conversion of the resource into production, but could also lead to competition with other
natural gas supply sources. For an individual country the situation could be more complex.
|The use of horizontal drilling in conjunction with hydraulic fracturing has greatly expanded the ability of
producers to profitably produce natural gas from low permeability geologic formations, particularly shale formations.
|References for World Shale Gas
 G.E. King, Apache Corporation, "Thirty Years of Gas Shale Fracturing: What Have We Learned?", prepared for the SPE Annual
Technical Conference and Exhibition (SPE 133456), Florence, Italy, (September 2010); and U.S. Department of Energy, DOE's Early Investment
in Shale Gas Technology Producing Results Today, (February 2011), web site.
 See: U.S. Energy Information Administration, "Drilling Sideways: A Review of Horizontal Well Technology and Its Domestic Application", DOE/EIA-TR-0565 (April 1993).
 U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Proved Reserves, 2009, web site.
 Examples of EIA work that has spurred or resulted from interest in this topic includes: U.S. Energy Information Administration,
AEO2011 Early Release Overview (Dec 2010); R. Newell, U.S. Energy Information Administration, "Shale Gas, A Game Changer for U.S.
and Global Gas Markets?", presented at the Flame - European Gas Conference, Amsterdam, Netherlands (March 2, 2010); H. Gruenspecht, U.S. Energy Information Administration, "International Energy Outlook 2010 With Projections to 2035", presented at Center for
Strategic and International Studies, Washington, D.C. (May 25, 2010); and R. Newell, U.S. Energy Information Administration, "The
Long-term Outlook for Natural Gas", presented to the Saudi Arabia - United States Energy Consultations, Washington, D.C. (February 2,
 Reserves refer to gas that is known to exist and is readily producible, which is a subset of the technically recoverable resource base
estimate for that source of supply. Those estimates encompass both reserves and that natural gas which is inferred to exist, as well as
undiscovered, and can technically be produced using existing technology. For example, EIA's estimate of all forms of technically recoverable natural gas resources in the U.S. for the Annual Energy Outlook 2011 is 2,552 trillion cubic feet, of which 827 trillion cubic feet
consists of unproved shale gas resources and 245 trillion cubic feet are proved reserves which consist of all forms of readily producible
natural gas including 34 trillion cubic feet of shale gas.
 "Total reserves, production climb on mixed results," Oil and Gas Journal (December 6, 2010), pp. 46-49.
 Includes 6,609 trillion cubic feet of world proven gas reserves (Oil and Gas Journal 2010); 3,305 trillion cubic feet of world mean estimates of inferred gas reserves, excluding the Unites States (USGS, World Petroleum Assessment 2000); 4,669 trillion cubic feet of world
mean estimates of undiscovered natural gas, excluding the United States (USGS, World Petroleum Assessment 2000); and U.S. inferred
reserves and undiscovered gas resources of 2,307 trillion cubic feet in the United States, including 827 trillion cubic feet of unproved
shale gas (EIA, AEO2011).
 The Department of State is the lead agency for the GSGI, and the other U.S. government agencies that also participate include: the
U.S. Agency for International Development (USAID); the Department of Interior's U.S. Geological Survey (USGS); Department of Interior's Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE); the Department of Commerce's Commercial Law
Development Program (CLDP); the Environmental Protection Agency (EPA), and the Department of Energy's Office of Fossil Energy
(DOE/FE). Web site.
|Map of the major shale gas plays in the lower 48 states including the sedimentary basins which contain them. Enlarge map.