Bakken Formation
Encyclopedia
The Bakken formation, initially described by geologist J.W. Nordquist in 1953,
is a rock unit from the Late Devonian to Early Mississippian age occupying about 200000 square miles (517,997.6 km²) of the subsurface of the Williston Basin
, underlying parts of Montana
, North Dakota
, and Saskatchewan
. The formation is entirely in the subsurface, and has no surface outcrop.
Besides being a widespread prolific source rock
for oil when thermally mature, there are also significant producible reserves of oil
within the Bakken formation itself. Oil was first discovered within the Bakken in 1951, but efforts to produce it have historically met with difficulties. An April 2008 USGS report estimated the amount of technically recoverable oil using technology readily available at the end of 2007 within the Bakken Formation at 3.0 to 4.3 Goilbbl, with a mean of 3.65 billion. The state of North Dakota also released a report that month which estimated that there are 2.1 Goilbbl 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. The most recent estimate places the figure at 18 billion barrels.
New rock fracturing technology available starting in 2008 has caused a recent boom in Bakken production. By the end of 2010 oil production rates had reached 458000 barrels (72,816.2 m³) per day outstripping the capacity to ship oil out of the Bakken. The production technology gain has led a veteran industry insider to declare the USGS estimates are too low.
, middle dolomite
, and upper shale. The shales were deposited in relatively deep anoxic marine conditions, and the dolomite was deposited as a coastal carbonate
bank during a time of shallower, well-oxygenated water. The middle dolomite member is the principal oil reservoir, roughly two miles (3.2 km) below the surface. Both the upper and lower shale members are organic-rich marine shale.
Porosities
in the Bakken average about 5%, and permeabilities
are very low, averaging 0.04 millidarcies—much lower than typical oil reservoirs, in today's terms a 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 drills 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 140 feet (42.7 m). Production is also enhanced by artificially fracturing the rock,
to allow oil to seep to the oil well.
thesis at the University of North Dakota
further sampled and analyzed the Bakken and calculated the hydrocarbon potential to be about 92 BBbls. These data were updated by Schmoker and Hester (1983) who estimated that the Bakken might contain a resource of 132 BBbls of oil in North Dakota and Montana. A research paper by USGS geochemist Leigh Price in 1999 estimated the total amount of oil contained in the Bakken shale ranged from 271 billion to 503 Goilbbl, with a mean of 413 Goilbbl. 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. However, Price died in 2000 before his research could be peer-reviewed and published. Nevertheless, 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 still there. New estimates of the amount of hydrocarbons generated by the Bakken were presented by Meissner and Banks (2000) and by Flannery and Kraus (2006). The first of these papers tested a newly developed computer model with existing Bakken data to estimate generated oil of 32 BBbls. The second paper used a more sophisticated computer program with extensive data input supplied by the ND Geological Survey and Oil and Gas Division. Early numbers generated from this information placed the value at 200 BBbls later revised to 300 BBbls when the paper was presented in 2006.". 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 167 Goilbbl of oil.
While these numbers would appear to indicate a very large oil resource, the percentage of this oil which might be extracted using current technology is another matter. Estimates of the Bakken's technically recoverable oil 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 2008 seem to indicate the lower range of recoverable estimates are more realistic with 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 3.0 to 4.3 Goilbbl, with a mean of 3.65 billion. Later that month, the state of North Dakota's report estimated that of the 167 Goilbbl of oil in-place in the North Dakota portion of the Bakken, 2.1 Goilbbl were technically recoverable with current technology.
In 2011, a senior manager at Continental Resources Inc. (CRI) 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 24 billion bbls. This considerable increase has been made possible by the combined use of horizontal drilling
, fracking, and a large number of wells drilled. While these technologies have been consistently in use since the 1980s, Bakken 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. CRI developed a technology allowing its rigs to move a few hundred yards on hydraulic "feet", increasing the rate of well completion.
, Richland County, Montana
, where production began in 2000 and is expected to ultimately total 270 Moilbbl. In 2007, production from Elm Coulee averaged 53000 oilbbl/d — more than the entire state of Montana a few years earlier.
New interest developed in 2007 when EOG Resources
of Houston, Texas reported that a single well it had drilled into an oil-rich layer of shale below Parshall, North Dakota
was anticipated to produce 700000 barrels (111,291.1 m³) of oil. This, 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. Those same sources show oil production in the North Dakota Bakken increasing 229%, from 2.2 Moilbbl in 2006 to 7.4 Moilbbl in 2007.
Montana°N date=July 2009°W
is a rock unit from the Late Devonian to Early Mississippian age occupying about 200000 square miles (517,997.6 km²) of the subsurface of the Williston Basin
Williston Basin
The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North and South Dakota, and southern Saskatchewan known for its rich deposits of petroleum and potash. The basin is a geologic structural basin but not a topographic depression; it is transected by the...
, underlying parts of Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
, North Dakota
North Dakota
North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....
, and Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
. The formation is entirely in the subsurface, and has no surface outcrop.
Besides being a widespread prolific source rock
Source rock
In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including...
for oil when thermally mature, there are also significant producible reserves of oil
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
within the Bakken formation itself. Oil was first discovered within the Bakken in 1951, but efforts to produce it have historically met with difficulties. An April 2008 USGS report estimated the amount of technically recoverable oil using technology readily available at the end of 2007 within the Bakken Formation at 3.0 to 4.3 Goilbbl, with a mean of 3.65 billion. The state of North Dakota also released a report that month which estimated that there are 2.1 Goilbbl 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. The most recent estimate places the figure at 18 billion barrels.
New rock fracturing technology available starting in 2008 has caused a recent boom in Bakken production. By the end of 2010 oil production rates had reached 458000 barrels (72,816.2 m³) per day outstripping the capacity to ship oil out of the Bakken. The production technology gain has led a veteran industry insider to declare the USGS estimates are too low.
Geology
The rock formation consists of three members: lower shaleShale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
, middle dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
, and upper shale. The shales were deposited in relatively deep anoxic marine conditions, and the dolomite was deposited as a coastal carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
bank during a time of shallower, well-oxygenated water. The middle dolomite member is the principal oil reservoir, roughly two miles (3.2 km) below the surface. Both the upper and lower shale members are organic-rich marine shale.
Porosities
Porosity
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...
in the Bakken average about 5%, and permeabilities
Permeability (fluid)
Permeability in fluid mechanics and the earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.- Units :...
are very low, averaging 0.04 millidarcies—much lower than typical oil reservoirs, in today's terms a light tight oil play. However, the presence of vertical to sub-vertical natural fractures makes the Bakken an excellent candidate for horizontal drilling
Directional drilling
Directional drilling is the practice of drilling non-vertical wells. It can be broken down into three main groups: Oilfield Directional Drilling, Utility Installation Directional Drilling Directional drilling (or slant drilling) is the practice of drilling non-vertical wells. It can be broken down...
techniques in which a well drills 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 140 feet (42.7 m). Production is also enhanced by artificially fracturing the rock,
to allow oil to seep to the oil well.
History of Bakken oil resource estimates
A landmark paper by Dow and a companion paper by Williams (1974) recognized the Bakken formation as a major source for the oil produced in the Williston Basin. These papers suggested that the Bakken was capable of generating 10 Goilbbl of oil (BBbls). Webster (1982, 1984) as part of a Master’sMaster's degree
A master's is an academic degree granted to individuals who have undergone study demonstrating a mastery or high-order overview of a specific field of study or area of professional practice...
thesis at the University of North Dakota
University of North Dakota
The University of North Dakota is a public university in Grand Forks, North Dakota, USA. Established by the Dakota Territorial Assembly in 1883, six years before the establishment of the state of North Dakota, UND is the oldest and largest university in the state and enrolls over 14,000 students. ...
further sampled and analyzed the Bakken and calculated the hydrocarbon potential to be about 92 BBbls. These data were updated by Schmoker and Hester (1983) who estimated that the Bakken might contain a resource of 132 BBbls of oil in North Dakota and Montana. A research paper by USGS geochemist Leigh Price in 1999 estimated the total amount of oil contained in the Bakken shale ranged from 271 billion to 503 Goilbbl, with a mean of 413 Goilbbl. 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
Oil exploration
Hydrocarbon exploration is the search by petroleum geologists and geophysicists for hydrocarbon deposits beneath the Earth's surface, such as oil and natural gas...
target. However, Price died in 2000 before his research could be peer-reviewed and published. Nevertheless, the drilling and production successes in much of the Bakken beginning with the Elm Coulee Oil Field
Elm Coulee Oil Field
Elm Coulee Oil Field was discovered in the Williston Basin in Richland County, eastern Montana, in 2000. It produces oil from the Bakken Formation and, as of 2007, is the "highest-producing onshore field found in the lower 48 states in the past 56 years." By 2007, the field had become one...
discovery in 2000 have proven correct his claim that the oil generated by the Bakken shale was still there. New estimates of the amount of hydrocarbons generated by the Bakken were presented by Meissner and Banks (2000) and by Flannery and Kraus (2006). The first of these papers tested a newly developed computer model with existing Bakken data to estimate generated oil of 32 BBbls. The second paper used a more sophisticated computer program with extensive data input supplied by the ND Geological Survey and Oil and Gas Division. Early numbers generated from this information placed the value at 200 BBbls later revised to 300 BBbls when the paper was presented in 2006.". 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 167 Goilbbl of oil.
While these numbers would appear to indicate a very large oil resource, the percentage of this oil which might be extracted using current technology is another matter. Estimates of the Bakken's technically recoverable oil 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 2008 seem to indicate the lower range of recoverable estimates are more realistic with 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
Byron Dorgan
Byron Leslie Dorgan is a former United States Senator from North Dakota and is now a senior policy advisor for a Washington, DC law firm. He is a member of the North Dakota Democratic-NPL Party, the North Dakota affiliate of the Democratic Party. In the Senate, he was Chairman of the Democratic...
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 3.0 to 4.3 Goilbbl, with a mean of 3.65 billion. Later that month, the state of North Dakota's report estimated that of the 167 Goilbbl of oil in-place in the North Dakota portion of the Bakken, 2.1 Goilbbl were technically recoverable with current technology.
In 2011, a senior manager at Continental Resources Inc. (CRI) 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 24 billion bbls. This considerable increase has been made possible by the combined use of horizontal drilling
Directional drilling
Directional drilling is the practice of drilling non-vertical wells. It can be broken down into three main groups: Oilfield Directional Drilling, Utility Installation Directional Drilling Directional drilling (or slant drilling) is the practice of drilling non-vertical wells. It can be broken down...
, fracking, and a large number of wells drilled. While these technologies have been consistently in use since the 1980s, Bakken 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. CRI developed a technology allowing its rigs to move a few hundred yards on hydraulic "feet", increasing the rate of well completion.
Oil production estimates
The greatest Bakken oil production comes from Elm Coulee Oil FieldElm Coulee Oil Field
Elm Coulee Oil Field was discovered in the Williston Basin in Richland County, eastern Montana, in 2000. It produces oil from the Bakken Formation and, as of 2007, is the "highest-producing onshore field found in the lower 48 states in the past 56 years." By 2007, the field had become one...
, Richland County, Montana
Richland County, Montana
-Demographics:As of the census of 2000, there were 9,667 people, 3,878 households, and 2,652 families residing in the county. The population density was 5 people per square mile . There were 4,557 housing units at an average density of 2 per square mile...
, where production began in 2000 and is expected to ultimately total 270 Moilbbl. In 2007, production from Elm Coulee averaged 53000 oilbbl/d — more than the entire state of Montana a few years earlier.
New interest developed in 2007 when EOG Resources
EOG Resources
EOG Resources is a Fortune 500 company with its headquarters in the Heritage Plaza building in downtown Houston, Texas. The company is one of the largest independent oil and natural gas companies in the United States with proven reserves in the United States, Canada, Trinidad and Tobago, the United...
of Houston, Texas reported that a single well it had drilled into an oil-rich layer of shale below Parshall, North Dakota
Parshall, North Dakota
Parshall is a city lying within the jurisdictional boundaries of the Mandan, Hidatsa, and Arikara Nation. It is located on the Fort Berthold Indian Reservation in Mountrail County, North Dakota, in the United States. Its population was 903 at the 2010 census...
was anticipated to produce 700000 barrels (111,291.1 m³) of oil. This, 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. Those same sources show oil production in the North Dakota Bakken increasing 229%, from 2.2 Moilbbl in 2006 to 7.4 Moilbbl in 2007.
Exploration and production
A number of publicly traded oil and gas companies have drilling rigs in the Bakken region, with varying asset prices, risks and potentials. These include Concho Resources Inc.,, Abraxas Petroleum Corporation, EOG Resources Inc., Continental Resources Inc., Whiting Oil & Gas Inc., Marathon Oil Corporation, QEP Resources, Brigham Exploration, Hess Corporation and Samson Oil and Gas Ltd.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.
Montana°N date=July 2009°W