Why have some estimates of undiscovered technically recoverable oil or gas changed so much from previous estimates?

Petroleum geologists have long known that oil and gas resources were present in “tight” or impermeable formations such as shale. But there was no way feasible way to extract that oil and gas, so they were not “technically recoverable” and were not be included in USGS assessment results.

Thanks to new technologies, oil and gas can now be extracted from “tight” formations, so they can be counted in assessments of undiscovered technically recoverable resources.

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Where in the United States is hydraulic fracturing being used for oil and gas extraction?

Hydraulic fracturing is used in many established oil and gas producing regions of the country as well as some areas new to the petroleum industry. Maps of major shale gas, tight gas, and tight oil basins are available from the U.S. Energy Information Administration, although not all of the shale basins shown currently have production.

Who is responsible for monitoring the issues associated with hydraulic fracturing and protecting our environment?

Individual states regulate many aspects of oil and gas exploration and production. Federal land managers, such as the Bureau of Land Management (BLM), the U.S. Forest Service (USFS), and the U.S. Fish and Wildlife Service (USFWS) have some oversight of oil and gas activities on the lands they manage. This includes conducting environmental impact...

When did hydraulic fracturing become such a popular approach to oil and gas production?

Hydraulic fracturing in vertical wells has been used for over fifty years to improve the flow of oil and gas from conventional reservoirs. However, the current practice of horizontal drilling coupled with multiple applications of hydraulic fracturing in a single well was pioneered in the late 1980s and has continued to evolve. Since the final...

What is hydraulic fracturing?

Hydraulic fracturing, informally referred to as “fracking,” is an oil and gas well development process that typically involves injecting water, sand, and chemicals under high pressure into a bedrock formation via the well. This process is intended to create new fractures in the rock as well as increase the size, extent, and connectivity of...

What is in the fluid injected into the ground during hydraulic fracturing?

In general, hydraulic fracturing fluid is composed of water, proppant (typically sand), and chemicals. A public website known as FracFocus has been established by industry that lists specific materials used in many, but not all, hydraulically fractured wells. Individual companies select a few chemicals to be used from hundreds that are available...

What is the USGS role related to hydraulic fracturing?

The USGS is a science research agency with no regulatory, land management, or enforcement powers. This includes: research and assessments on the location, quantity, and quality of unconventional oil and gas resources whose production could involve hydraulic fracturing. Resource assessments estimate the quantity of oil and gas that is yet to be...

How much water does the typical hydraulically fractured well require?

There isn’t really a “typical” fractured well because the amount of water used depends on the rock formation, the operator, whether the well is vertical or horizontal, and the number of portions (or stages) of the well that are fractured. In addition, some water is recycled from fluids produced by the well, so the net consumption might be smaller...

What environmental issues are associated with hydraulic fracturing?

The actual practice of hydraulic fracturing (or “fracking”) is only a small part of the overall process of drilling, completing, and producing an oil and gas well. Environmental issues that are specifically related to hydraulic fracturing include: water availability spills of chemicals at the surface impacts of sand mining for use in the hydraulic...

How is hydraulic fracturing related to earthquakes and tremors?

Reports of hydraulic fracturing causing felt earthquakes are extremely rare. However, wastewater produced by wells that were hydraulic fractured can cause “induced” earthquakes when it is injected into deep wastewater wells. Wastewater disposal wells operate for longer durations and inject much more fluid than the hydraulic fracturing operations...

How does hydraulic fracturing affect the surface or landscape of an area?

An area undergoing production of oil or gas using hydraulic fracturing technology shares many features with areas where conventional oil or gas is being developed, including: Roads Pipelines Compressor stations Processing facilities. Features that are unique to areas in which hydraulic fracturing is used include: Fewer but larger drilling pads,...

How does hydraulic fracturing differ from traditional petroleum development methods?

In a conventional oil or gas field, where the oil or gas is in relatively porous and permeable rock (i.e. the pores are connected), the oil or gas can usually flow naturally from the reservoir rock to the wellbore. Nonetheless, a variety of techniques are often used to improve the flow of oil or gas, including hydraulic fracturing. Rock formations...

Can hydraulic fracturing impact the quality of groundwater or surface water?

Conducted properly, hydraulic fracturing (or “fracking”) has little possibility of contaminating water supplies. Properly constructed wells prevent drilling fluids, hydraulic fracturing fluids, deep saline formation waters, or oil and gas from entering aquifers. Carefully constructed and operated well sites have the ability to contain potential...
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Date published: December 22, 2017

Re-Assessing Alaska's Energy Frontier

Less than 80 miles from Prudhoe Bay, home to the giant oil fields that feed the Trans-Alaska Pipeline, lies the site of USGS’ latest oil and gas assessment: the National Petroleum Reserve-Alaska and adjacent areas. Managed by the Bureau of Land Management, the NPR-A covers 22.8 million acres, more than the entire state of South Carolina.

Date published: February 2, 2017

Forecasting the World’s Energy Resources

It is difficult to overstate the importance of energy to the American economy.  Managing this vital sector depends on knowing how many energy resources we have, how many we use and need, and how these resources are transported.

Date published: November 15, 2016

USGS Estimates 20 Billion Barrels of Oil in Texas’ Wolfcamp Shale Formation

This is the largest estimate of continuous oil that USGS has ever assessed in the United States.

Date published: June 8, 2016

USGS Estimates 66 Trillion Cubic Feet of Natural Gas in Colorado’s Mancos Shale Formation

This is the second-largest assessment of potential shale & tight gas resources that the USGS has ever conducted.

Date published: December 17, 2015

USGS Estimates 53 Trillion Cubic Feet of Gas Resources in Barnett Shale

The Barnett Shale contains estimated mean volumes of 53 trillion cubic feet of shale natural gas, 172 million barrels of shale oil and 176 million barrels of natural gas liquids, according to an updated assessment by the U.S. Geological Survey. This estimate is for undiscovered, technically recoverable resources.

Date published: October 6, 2015

USGS Estimates 21 Million Barrels of Oil and 27 Billion Cubic Feet of Gas in the Monterey Formation of the San Joaquin Basin, California

The Monterey Formation in the deepest parts of California’s San Joaquin Basin contains an estimated mean volumes of 21 million barrels of oil, 27 billion cubic feet of gas, and 1 million barrels of natural gas liquids, according to the first USGS assessment of continuous (unconventional), technically recoverable resources in the Monterey Formation.

Date published: March 25, 2015

Appalachian Basin Energy Resources — A New Look at an Old Basin

Appalachian coal and petroleum resources are still available in sufficient quantities to contribute significantly to fulfilling the nation’s energy needs, according to a recent study by the U.S. Geological Survey.

Date published: June 20, 2012

USGS Releases Unconventional Gas Estimates for Five East Coast Basins

Using a geology-based assessment method, the U.S. Geological Survey estimated a mean undiscovered natural gas resource of 3.9 trillion cubic feet and a mean undiscovered natural gas liquids resource of 135 million barrels in continuous accumulations within five East Coast Mesozoic basins, according to a new USGS report.  

Date published: April 10, 2008

3 to 4.3 Billion Barrels of Technically Recoverable Oil Assessed in North Dakota and Montana’s Bakken Formation—25 Times More Than 1995 Estimate—

North Dakota and Montana have an estimated 3.0 to 4.3 billion barrels of undiscovered, technically recoverable oil in an area known as the Bakken Formation.

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Image shows squares of permafrost
December 31, 2017

Permafrost in the National Petroleum Reserve-Alaska

Permafrost forms a grid-like pattern in the National Petroleum Reserve-Alaska, a 22.8 million acre region managed by the Bureau of Land Management on Alaska's North Slope. USGS has periodically assessed oil and gas resource potential there. These assessments can be found here.

Image shows a map of the Mancos Shale and the assessment units
June 3, 2016

2016 Mancos Assessment Map

A map showing the Mancos Shale and the USGS assessment units within the formation.

Oil and Gas 4
December 31, 2015

Oil Well being Drilled into the Bakken Formation

Oil well being drilled into the Bakken Formation in North Dakota in 2015.

Photo of an active oil and gas pad on Bureau of Land Management lands near Canyonlands National Park, Utah.
November 30, 2014

Active oil and gas pad near Canyonlands National Park

Active oil and gas pad on Bureau of Land Management lands near Canyonlands National Park, Utah.

Oil and Gas Resources of the Arctic Alaska Petroleum Province
December 31, 2006

Oil and Gas Resources of the Arctic Alaska Petroleum Province

Arctic Alaska Petroleum Province, showing locations of principal geologic features. AF, Alpine oil field; ANWR, Arctic National Wildlife Refuge; NPRA, National Petroleum Reserve in Alaska; PB, Prudhoe Bay oil field

A map showing the Barnett Shale assessment area in east Texas

A map showing the Barnett Shale assessment area in east Texas

Attribution: Energy and Minerals
Image shows a desert landscape with mountains in the background

The Western Permian Basin

In West Texas and southwestern New Mexico lies the Permian Basin, one of the most productive oil and gas basins in the United States. USGS has assessed both conventional and continuous oil and gas resources throughout the Permian Basin. These assessments, as well as other USGS energy research for the Permian Basin, can be found


A map showing the Barnett Shale assessment area in east Texas

A map showing the Barnett Shale assessment area in east Texas

Attribution: Energy and Minerals