HOME

TheInfoList



OR:

The Bakken Formation () is a
rock unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize ...
from the Late Devonian to Early Mississippian age occupying about of the subsurface of the Williston Basin, underlying parts of
Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...
,
North Dakota North Dakota () is a U.S. state in the Upper Midwest, named after the indigenous Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north and by the U.S. states of Minnesota to the east, ...
,
Saskatchewan Saskatchewan ( ; ) is a Provinces and territories of Canada, province in Western Canada, western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on t ...
and
Manitoba Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population o ...
. The formation was initially described by
geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althou ...
J. W. Nordquist in 1953. The formation is entirely in the subsurface, and has no surface outcrop. It is named after Henry O. Bakken (1901–1982), a farmer in Tioga, North Dakota, who owned the land where the formation was initially discovered while drilling for oil. Besides the Bakken formation being a widespread prolific
source rock In petroleum geology, source rock is rock which has generated hydrocarbons or which could generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been depo ...
for oil when thermally mature, significant producible oil reserves exist within the rock unit itself. Oil was first discovered within the Bakken in 1951, but past efforts to produce it have faced technical difficulties. In April 2008, a USGS report estimated the amount of recoverable oil using technology readily available at the end of 2007 within the Bakken Formation at 3.0 to , with a mean of 3.65 billion. Simultaneously the state of North Dakota released a report with a lower estimate of of technically recoverable oil in the Bakken. Various other estimates place the total reserves, recoverable and non-recoverable with today's technology, at up to 24 billion barrels. A recent estimate places the figure at 18 billion barrels. In April 2013, the U.S. Geological Survey released a new figure for expected ultimate recovery of 7.4 billion barrels of oil. The application of hydraulic fracturing and
directional drilling Directional drilling (or slant drilling) is the practice of drilling non-vertical bores. It can be broken down into four main groups: oilfield directional drilling, utility installation directional drilling, directional boring (horizontal dire ...
technologies has caused a boom in Bakken oil production since 2000. By the end of 2010, oil production rates had reached per day, thereby outstripping the pipeline capacity to ship oil out of the Bakken. There is some controversy over the safety of shipping this crude oil by rail due to its volatility. This was illustrated by the 2013 Lac-Mégantic rail disaster, in which a unit train carrying 77 tank cars full of highly volatile Bakken oil through
Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirte ...
from North Dakota to the
Irving Oil Refinery The Irving Oil Refinery is a Canadian oil refinery located in Saint John, New Brunswick. It is currently the largest oil refinery in Canada, capable of producing more than of refined products per day. Over 80 per cent of the production is exported ...
in
New Brunswick New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...
derailed and exploded in the town centre of Lac-Mégantic. It destroyed 30 buildings (half the downtown core) and killed 47 people. The explosion was estimated to have a one-kilometre (0.62 mi) blast radius. As of January 2015, estimates varied on the
break-even Break-even (or break even), often abbreviated as B/E in finance, (sometimes called point of equilibrium) is the point of balance making neither a profit nor a loss. Any number below the break-even point constitutes a loss while any number above it ...
oil price for drilling Bakken wells. The North Dakota Department of Natural Resources estimated overall break-even to be just below US$40 per barrel. An analyst for Wood Mackenzie said that the overall break-even price was US$62/barrel, but in high-productivity areas such as Sanish Field and Parshall Oil Field, the break-even price was US$38–US$40 per barrel.


Geology

The rock formation consists of three members: lower shale, middle
dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...
, and upper shale. The shales were deposited in relatively deep anoxic marine conditions, and the dolomite was deposited as a coastal
carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate ...
bank during a time of shallower, well-oxygenated water. The middle dolomite member is the principal oil reservoir, roughly below the surface. Both the upper and lower shale members are organic-rich marine shale.


Oil and gas

The Bakken formation has emerged in recent years as one of the most important sources of new oil production in the United States. Most Bakken drilling and production has been in North Dakota, although the formation also extends into Montana and the Canadian provinces of Saskatchewan and Manitoba. As of 2013, the Bakken was the source of more than ten percent of all US oil production. By April 2014, Bakken production in North Dakota and Montana exceeded . As a result of increased production from the Bakken, and long-term production declines in
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...
and
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
, North Dakota as of 2014 was the second-largest oil-producing state in the US, behind only
Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
in volume of oil produced. Bakken production has also increased in
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...
, although to a lesser degree than in the US, since the 2004 discovery of the Viewfield Oil Field in Saskatchewan. The same techniques of horizontal drilling and multi-stage massive hydraulic fracturing are used. In December 2012, 2,357 Bakken wells in Saskatchewan produced a record high of . The Bakken Formation also produces in Manitoba, but the yield is small, averaging less than in 2012.


Drilling and completion

Most Bakken wells are drilled and completed in the middle member. Many wells are now being drilled and completed in the basal Sanish/Pronghorn member and in the underlying Three Forks Formation, which the North Dakota Department of Mineral Resources treats as part of the Bakken for oil production statistical purposes.
Porosities Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...
in the Bakken averages about 5%, and permeabilities are very low, averaging 0.04 millidarcys—much lower than typical oil reservoirs, in today's terms an unconventional light tight oil play. However, the presence of vertical to sub-vertical natural fractures makes the Bakken an excellent candidate for horizontal drilling techniques in which a well is drilled horizontally along bedding planes, rather than vertically through them. In this way, a borehole can contact many thousands of feet of oil reservoir rock in a unit with a maximum thickness of only about . Production is also enhanced by artificially fracturing the rock, to allow oil to seep to the oil well.
Hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The under ...
(H2S, also known as sour gas) is found to varying degrees in crude petroleum. The gas is flammable, corrosive, poisonous, and explosive; thus, oil with higher levels of H2S presents challenges such as "health and environmental risks, corrosion of wellbore, added expense with regard to materials handling and pipeline equipment, and additional refinement requirements." Bakken oil has historically been characterized as "sweet", meaning that it has little or no H2S. However, increased concentration of H2S over time has been observed in some Bakken wells, believed to be due to certain completion practices, such as hydraulic fracturing into neighboring formations, that may contain high levels of H2S. Some other formations in the Williston Basin have always produced "sour" (high H2S) crude oil, and because sweet oil brings a higher price, oil transporters suspect that some sour oil is being blended into sweet Bakken crude. H2S in crude oil is being investigated as a possible cause of the explosive nature of the Lac-Mégantic rail disaster.
Pipeline transport Pipeline transport is the long-distance transportation of a liquid or gas through a system of Pipe (fluid conveyance), pipes—a pipeline—typically to a market area for consumption. The latest data from 2014 gives a total of slightly less than ...
operator Enbridge no longer accepts crude with more than five parts per million H2S, citing safety concerns. Increased US oil production from hydraulically fractured tight oil wells in formations such as the Bakken was mostly responsible for the decrease in US oil imports since 2005. The US imported 52% of its oil in 2011, down from 65% in 2005. Hydraulically fractured wells in the Bakken, Eagle Ford, and other tight oil targets enabled US crude oil production to rise in September 2013 to the highest output since 1989.


History of Bakken oil resource estimates


Oil in place

A research paper by
USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
geochemist Leigh Price in 1999 estimated the total amount of oil contained in the Bakken shale ranged from , with a mean of . While others before him had begun to realize that the oil generated by the Bakken shales had remained within the Bakken, it was Price, who had spent much of his career studying the Bakken, who particularly stressed this point. If he was right, the large amounts of oil remaining in this formation would make it a prime oil exploration target. Price died in 2000 before his research could be peer-reviewed and published. The drilling and production successes in much of the Bakken beginning with the Elm Coulee Oil Field discovery in 2000 have proven correct his claim that the oil generated by the Bakken shale was there. In April 2008, a report issued by the state of North Dakota Department of Mineral Resources estimated that the North Dakota portion of the Bakken contained of oil in place.


Recoverable oil

Although the amount of oil in place is a very large oil resource, the percentage that can be extracted with current technology is another matter. Estimates of the Bakken's recovery factor have ranged from as low as 1%—because the Bakken shale has generally low porosity and low permeability, making the oil difficult to extract—to Leigh Price's estimate of 50% recoverable. Reports issued by both the USGS and the state of North Dakota in April 2013 estimated up to 7.4 billion barrels of oil can be recovered from the Bakken and Three Forks formations in the Dakotas and Montana, using current technology. The flurry of drilling activity in the Bakken, coupled with the wide range of estimates of in-place and recoverable oil, led North Dakota senator Byron Dorgan to ask the USGS to conduct a study of the Bakken's potentially recoverable oil. In April 2008 the USGS released this report, which estimated the amount of technically recoverable, undiscovered oil in the Bakken formation at , with a mean of 3.65 billion. Later that month, the state of North Dakota's report estimated that of the of oil in place in the North Dakota portion of the Bakken, were technically recoverable with current technology. In 2011, a senior manager at
Continental Resources Continental Resources, Inc. is a petroleum and natural gas exploration and production company headquartered in Oklahoma City. The company was founded by Harold Hamm in 1967 at the age of 21 as Shelly Dean Oil Company, originally named for Hamm's ...
Inc. (CLR) declared that the "Bakken play in the Williston basin could become the world's largest discovery in the last 30–40 years," as ultimate recovery from the overall play is now estimated at . (Note: the recent discoveries off the coast of
Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
should be greater, with proven reserves of 30 billion, and a potential for 50 to 80.) This considerable increase has been made possible by the combined use of horizontal drilling, hydraulic fracturing, and a large number of wells drilled. While these technologies have been consistently in use since the 1980s, the Bakken trend is the place where they are being most heavily used: 150 active rigs in the play and a rate of 1,800 added wells per year. An April 2013 estimate by the USGS projects that of undiscovered oil can be recovered from the Bakken and Three Forks formations and 6.7 trillion cubic feet of natural gas and 530 million barrels of natural gas liquids using current technology. The Energy Information Administration (EIA), the statistics service of the Department of Energy, estimated in 2013 that there were 1.6 billion barrels and 2.2 trillion cubic feet (tcf) of technically recoverable oil and natural gas in the Canadian portion of the Bakken formation. Crescent Point Energy and other operators are implementing waterfloods in the Bakken Formation of the Viewfield Oil Field in Saskatchewan. Some believe that
waterflooding In the oil industry, waterflooding or water injection is where water is injected into the oil reservoir, to maintain the pressure (also known as voidage replacement), or to drive oil towards the wells, and thereby increase production. Water inje ...
can raise the recovery factor at Viewfield from 19 percent to more than 30 percent, adding 1.5 to two billion barrels of additional oil.


Proved reserves

The US EIA reported that proved reserves in the Bakken/Three Forks were 2.00 billion barrels of oil as of 2011.


History of Bakken oil

The Bakken formation has produced oil since 1953, when the #1 Woodrow Starr was completed in North Dakota by Stanolind Oil and Gas.


Southwest pinch-out

A major advance in extracting oil from the Bakken came in 1995, when geologist Dick Findley realized that the dolomitic Middle member of the Bakken Formation was a better exploration target than the upper or lower members. Although the middle member held less oil in place than the organic shales both above and below, it was able to maintain open fractures more than the shales. Horizontal wells in the middle Bakken were used successfully to develop the Elm Coulee Field in Montana. The 2000 discovery of the Elm Coulee Oil Field,
Richland County, Montana Richland County is a county in the U.S. state of Montana. As of the 2020 census, the population was 11,491. Its county seat is Sidney. Richland County was created by the Montana Legislature in 1914 from part of Dawson County. An early prop ...
, where production is expected to ultimately total , drew a great deal of attention to the trend where oil was trapped along the Bakken pinchout. In 2007, production from Elm Coulee averaged — more than the entire state of Montana a few years earlier. The Mondak Field to the southeast of Elm Coulee extended the productive pinchout trend into North Dakota. Elm Coulee was key to later Bakken development because it combined horizontal wells and hydraulic fracturing, and targeted the dolomitic middle Bakken member rather than the shales of the upper or lower Bakken.


East side trap

New interest developed in 2006 when EOG Resources reported that a single well it had drilled into an oil-rich layer of shale near Parshall, North Dakota, was anticipated to produce of oil. At Parshall, the abrupt eastern limit of the field is formed by the extent of thermally mature Bakken shale; shale farther east is thermally immature, and unproductive. The Parshall Oil Field discovery, combined with other factors, including an oil-drilling tax break enacted by the state of North Dakota in 2007, shifted attention in the Bakken from Montana to the North Dakota side. The number of wells drilled in the North Dakota Bakken jumped from 300 in 2006 to 457 in 2007. The viability of the play in North Dakota west of the Nesson Anticline was uncertain until 2009, when Brigham Oil & Gas achieved success with larger hydraulic fracturing treatments, with 25 or more stages. According to the North Dakota Department of Mineral Resources, daily oil production per well reached a plateau at 145 barrels in June 2010. Although the number of wells tripled between June 2010 and December 2012, oil production per well remained essentially unchanged. However, as more wells were brought online, total oil produced continued to increase until it peaked in mid-2015 at 1.15 million barrels per day. The increase ended because of a slow decline in daily production per well that began in 2013, down to 115 barrels in mid-2015. The peak production value reported by the EIA is about 9% larger. The EIA also reports that the Bakken rig count dropped about 60% over the year ending in October 2015 in response to the collapsing price of oil, while the new-well (initial) oil production per rig increased by 40%, both apparently plateauing at that time. (The production rate from fracked wells decreases more rapidly than from conventional wells drilled in more permeable rock.)


Exploration and production

Several public companies have drilling rigs in the Bakken trend. These include EOG Resources,
Continental Resources Continental Resources, Inc. is a petroleum and natural gas exploration and production company headquartered in Oklahoma City. The company was founded by Harold Hamm in 1967 at the age of 21 as Shelly Dean Oil Company, originally named for Hamm's ...
,
Chord Energy Chord Energy Corporation is a company engaged in hydrocarbon exploration and hydraulic fracturing in the Williston Basin in North Dakota and Montana. It is organized in Delaware and headquartered in Houston, Texas, with an office in Williston, No ...
, Marathon Oil Corporation,
Diamondback Energy Diamondback Energy is a company engaged in hydrocarbon exploration headquartered in Midland, Texas. As of December 31, 2020, the company had of estimated proved reserves, of which 52% was petroleum, 24% was natural gas, and 24% was natural gas ...
, and Hess Corporation. In Canada, operators include Ridgeback Resources, and
Crescent Point Energy Crescent Point Energy Corp. is an oil and gas company based in Calgary, Alberta, Canada. The company focuses primarily on light oil production in southern Saskatchewan and central Alberta. Since its inception in 2001, Crescent Point has signific ...
. LIG Assets, Inc. elected to participate in a 10% industry position in a group of oil leases located in the Bakken formation in North Dakota. The leases comprise approximately in McKenzie County, the most productive oil producing county in the state. Some companies have sold assets in the Bakken, in favor of exploring the Permian Basin in Texas, due in part to the higher cost of transport to major markets closer to tidewater with inexpensive access to foreign oil. Oil extraction in Bakken field declined by around 20% from mid-2015 to mid-2016 and then remained rather stable until mid-2017.


Worker safety versus productivity

With the persistently low price of oil in 2015, there was pressure on rigs to maximize drilling speed, with associated additional risks to the crews. It was reported that on average, an oil worker died in the Bakken every six weeks. One company offered workers daily bonuses of $150 for drilling quickly, while those who proceeded more slowly, exercising caution, were offered only $40 a day. The well owner may avoid liability for accidents if the blame can be assigned to the rig subcontractor. Statutes have been established to prevent this in four other oil-producing states:
Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
,
Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is bord ...
,
New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...
and
Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to t ...
.


Oil and gas infrastructure

The great increases in oil and gas production have exceeded the area's pipeline capacity to transport hydrocarbons to markets. There is only one refinery in the area. As a result, the oil and gas prices received have been much lower than the normal North American index prices of West Texas Intermediate for oil and
Henry Hub The Henry Hub is a distribution hub on the natural gas pipeline system in Erath, Louisiana, owned by Sabine Pipe Line LLC, a subsidiary of EnLink Midstream Partners LP who purchased the asset from Chevron Corporation in 2014. Due to its importanc ...
for gas. The shortage of pipeline capacity has caused some producers to ship oil out of the area by more expensive methods of truck or railroad. It was Bakken crude oil carried by train that caught fire in the deadly 2013 Lac-Mégantic rail disaster in
Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirte ...
. Part of the disaster at Lac-Mégantic has been blamed on the fact that much of the highly volatile Bakken oil was mislabeled as lower risk oil and was being shipped in substandard tank cars not designed to contain it. Because of the shortage of pipeline capacity out of North Dakota, over half of its production is sent to market by rail.
BNSF Railway BNSF Railway is one of the largest freight railroads in North America. One of seven North American Class I railroads, BNSF has 35,000 employees, of track in 28 states, and nearly 8,000 locomotives. It has three transcontinental routes that ...
and
Canadian Pacific Railway The Canadian Pacific Railway (french: Chemin de fer Canadien Pacifique) , also known simply as CPR or Canadian Pacific and formerly as CP Rail (1968–1996), is a Canadian Class I railway incorporated in 1881. The railway is owned by Canad ...
reported to
Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over t ...
officials that about 50 Bakken oil trains pass through the state each week, mostly through the Twin Cities of
Minneapolis–Saint Paul Minneapolis–Saint Paul is a metropolitan area in the Upper Midwest, Upper Midwestern United States centered around the confluence of the Mississippi River, Mississippi, Minnesota River, Minnesota and St. Croix River (Wisconsin–Minnesota) ...
. At least 15 major accidents involving crude oil or
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
trains have occurred in the United States and Canada since 2006, and most small cities such as Lac-Megantic are not prepared for oil train explosions and fires. In March 2013, Canadian pipeline company Enbridge completed a pipeline to take North Dakota oil north into Canada, where it hooks up to Enbridge's main pipeline delivering western Canadian oil to refineries in the
American Midwest The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of the United States. I ...
. Unlike the rejected cross-border
Keystone XL Pipeline The Keystone Pipeline System is an oil pipeline system in Canada and the United States, commissioned in 2010 and owned by TC Energy and as of 31 March 2020 the Government of Alberta. It runs from the Western Canadian Sedimentary Basin in Alberta ...
, the pipeline project to carry American crude across the border was approved by the US government without controversy. Absent the infrastructure to produce and export
natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbon d ...
, it is merely burned on the spot; a 2013 study estimated the cost at $100 million per month.


Effects of the boom

The North Dakota oil boom has given those who own mineral rights large incomes from lease bonuses and royalties. The boom has reduced unemployment and given the state of North Dakota a billion-dollar budget surplus. North Dakota, which ranked 38th in per capita
gross domestic product Gross domestic product (GDP) is a monetary measure of the market value of all the final goods and services produced and sold (not resold) in a specific time period by countries. Due to its complex and subjective nature this measure is of ...
(GDP) in 2001, rose steadily with the Bakken boom, and now has per capita GDP 29% above the national average. The industrialization and population boom has put a strain on water supplies, sewage systems, available housing and government services of the small towns and ranches in the area. Increasing economic prosperity has also brought increasing crime and social problems.


See also

* Double H Pipeline * Pony Express Pipeline * Dakota Access Pipeline


References


External links


Geology.Com: ''Bakken formation''
accessed 4 March 2009
US Geological Survey: ''Assessment of undiscovered oil resources in the Devonian-Mississippian Bakken Formation''
PDF file, retrieved 4 March 2009
Boom! Behind the Bakken
Documentary produced by Montana PBS
Three tiers of US shale plays
{{WCSB, Saskatchewan=yes Geologic formations of Montana Geologic formations of North Dakota Geologic formations of Saskatchewan Devonian System of North America Devonian Montana Devonian North Dakota Devonian Saskatchewan Mississippian Series Mississippian United States Dolomite formations Shale formations Shale formations of the United States Deep marine deposits Shallow marine deposits Source rock formations Western Canadian Sedimentary Basin Oil-bearing shales in Canada Oil-bearing shales in the United States Oil fields in North Dakota