It's oil found, or expected to be present, within a reservoir with low permeability, i.e. a tight reservoir.
The term is applied to a play where trapped petroleum accumulations are expected to be pervasive throughout a large area and that are not significantly affected by hydrodynamic influences (also called resource play or continuous-type deposits).
Economic production from tight oil formations requires the same hydraulic fracturing and often uses the same horizontal well technology used in the production of shale gas.
While sometimes called «shale oil», tight oil should not be confused with oil shale, which is shale rich in kerogen, a precursor to oil, or shale oil, which is oil produced from oil shales.
The International Energy Agency (IEA) recommends using the term «light tight oil» for oil produced from shales or other very low permeability formations.
The World Energy Resources 2013 report by the World Energy Council uses the terms «tight oil» and «shale-hosted oil».
Сompanies extract shale oil by fracturing the rock formations that contain the layers of oil.
Shale oil comprises more than 30% of the onshore production of crude oil in the lower 48 states.
Today the United States is the world’s largest crude-oil producer, according to the Energy Information Administration (EIA).
Shale oil extraction (fracking) benefits from innovative drilling techniques.
Global technically recoverable oil shale reserves have been estimated at about 2,8 - 3.3 trillion barrels of shale oil, with the largest reserves in the US, which is thought to have 1,5 - 2,6 trillion barrels.
Shale Oil extracted
After operators drill the well a horizontal deviation is drilled.
This method allows them to gain access to the oil-bearing reservoir rock.
The sand holds the fractures open.
That allows the oil to seep into the well.
It became more affordable when Brigham Oil & Gas successfully split a single horizontal leg.
The company fracked each leg independently, providing a higher return on the investment.
This technique propelled North Dakota field production from 7 million barrels in January 2010 to 46 million in October 2019.
The field has layers of dense, oil-bearing rock about 2 miles underground.
In these fields, drillers use multistage fracking to create longer cracks.
They perforate short segments of the production casing.
That allows them to concentrate the bursts of water in targeted spots.
The initial drilling only accounts for 40% of the total cost.
Extracting the oil costs roughly $1 million for each well.
That made shale oil extraction profitable when oil reached $100 a barrel.
That's allowed them to stay in business despite lower oil prices and keep drilling.
When they stop extracting, they store the oil in the ground.
They call these wells DUCs for drill and cover.
They can safely wait until oil prices return to $60 a barrel.
At that point, they can start extracting oil from the wells they've already drilled.
That will keep prices from rising much above that price level.
The latest oil price forecast shows they will remain in that range.
Investor sentiment has more influence on oil prices.
They trade oil on global commodities exchanges.
Traders can bid the price of oil down or up, depending on their assumptions of factors affecting oil.
They created an asset bubble in oil in 2008.
They drove the price of West Texas Intermediate up to $145 a barrel.
These traders are the main factor that makes oil prices so high.
The volatility in oil prices made gas prices in 2008 do the same thing.
As prices remained in that range, shale oil producers started drilling wells.
They flooded the market, driving prices down in 2014.
By that point, they had learned how to extract more cheaply.
That created a U.S. shale oil boom that led to a bust.
That's a total savings of $4 billion.
As a result, gasoline prices fell.
This helps low-income families more since they spend a higher proportion of their income on necessities such as transportation.
- Fracking is controversial for three reasons.
First, it uses a lot of natural resources.
Before drillers can extract the first drop of oil, they must pump in 800 truckloads of water.
They also use hundreds of truckloads of other material.
Unless the water is already on site, it must be trucked in.
There it is stored in huge tanks before the fracking can begin.
The composition of the fracking fluid is proprietary to each company.
- fracking can affect drinking water.
If the fields are near groundwater reservoirs, the fracking fluid can be directly injected into drinking water.
In areas with low water availability, the drillers are competing with nearby communities for this necessary resource.
- Fracking may also cause earthquakes.
They cause earthquakes by pumping wastewater into special disposal wells.
The high-pressure pumping may trigger shifts in the fault lines.
As a result, the quakes can occur far from the disposal wells