The Kern River Oil Field in California’s Central Valley, even to an expert’s eyes, looks like a normal oil field. When it was first discovered, in 1899, analysts said that only 10% of its “viscous content” could be extracted.
After 40 years of production and extraction, it was estimated to still contain 54 million barrels of recoverable oil, and 278 million barrels already used. In the next 44 years, its output will be 736 million barrels, and with more 970 million barrels to come.
In 2007, the oil company Chevron, announced that its total output had reached two million barrels. Today the field still produces 80000 barrels a day, and it is estimated to contain still 627 million barrels. A theory called Hubbert curve, explains how the output of an oil field should follow a bell-shaped trajectory, and peak when half of the known oil has been extracted. Most of oilfields in the world “defeated” this theory. This happens because, with the help of technology, oil companies can extract more oil than projected, using new extraction techniques. Leaps in extraction technology have led to tapping oil in once inaccessible areas and in places where drilling used to be too expensive.
Today, the biggest part of known oil sites is left behind. Earth’s proven reserves of oil are estimated between 1.1 and 1.3 trillion barrels, and they will probably run out in 40 years. But they are just estimates, they’re not proved numbers. The amount of oil that could be recovered with today’s technologies will probably stay at the same level in 10 years from today, thanks to the introduction of new extraction techniques.
Today only 35% of the oil in the average oil field is recovered, and two thirds of it is left behind underground.
Only one third of the sedimentary basins of our planet has been deeply scanned with modern technology to check the presence of oil.
This happens because an oil reservoir is a rocky underground structure, which seems to have no room for oil at all. It is contained in a huge amount of small holes and microfractures that entrapmicroscopic drops of black gold, with natural gases and water.
This geological formation was created by nature over millions of years ago. Everything started when vegetation and dead microorganisms piled up at the bottom of seas, decomposing and turning the organical sediments into today’s oil and gas.
When drilling machines dig into an oil reservoir, it works like a bottle of champagne: the pressure contained underground pushes the oil to the surface with rocks and other debris. This goes on until the pressure ends, usually after several years.
This is the primary stage of recovery, that can yield between 10 and 15 percent of the total amount of oil. One third of the oil left in is called immobile oil, because there’s no technique yet able to extract it. The remaining two thirds will need “help” to be extracted. In the secondary recovery, operators inject water and natural gas in the reservoir, to help some of the remaining oilto come out of the wells.
They do this because through the injection of gases, they restore the previous amount of pressure, allowing it to push some oil to the surface. A very important development is the horizontal well, that with its L-shaped structure is able to deliver more oil that the usual vertical-shaped well.
Primary and secondary recovery can extract together a rate between 20 and 40 percent.
In the tertiary recovery, it is necessary to make the remaining oil less dense: to accomplish this operation, experts can use heat, chemicals or bacteria.
The incendiary method: this method requires to burn part of the reservoir by injecting air underground. In this way, heat makes oil less viscous, the combustion produces carbon dioxide, which restores pressure and pushes part of the oil into the wells, and the fire breaks the larger molecules of oil, making it more mobile.
The chemical method: a particular type of substances called surfactants are injected in the ground, to help oil detach from the rocks and flow more smoothly into the wells.
The biological method: with the injection of bacteria, it grows in the space between the rock and oil, helping to release it. Usually this method takes several days, because bacteria need to grow to a complete-stadium.
Today we are running out of “Easy Oil.” But luckily, what today is the difficult oil, tomorrow will be the easy oil, thanks to technology.
By 2030 we will have consumed700 billion barrels of out reserves. If the latest estimates are correct, there will be enough oil for the entire 21st century.
In some years there will be the problem of how to use the rest of the oil without wasting it with unacceptable energy production ways and without destroying and polluting the environment and climate of planet Earth.
Filippo Albertino (4D)