what happens after crude oil is extracting from the ground?

Question

With the millions of barrels of oil being extracted from underground, this surely must leave gigantic empty spaces ?

But each barrel extracted must leave a space of one barrel?

Answer 1

No.Gigantic empty spaces ? Full of what ? Nature hates void (Lavoisier)
Let's start from beginning.
Oil is found in rocks like sandstone or limestone called 'reservoir rocks'. The oil is filling the pore space or the fractures (which is a kind of porosity as well). BUT OIL IS NOT THE ONLY ONE TO DO THIS. Once you reach a certain depth which varies depending on the region (surface to more than 600 ft in desert) there is no air in the pore of the rock. The pores are full with fluid, either fresh water (usually at surface), salty water and brine (deeper), oil, gases (CO2, Methan or mixed gas : usually, with the pressure, these gas are liquid). So when you produce oil, the 'nearest fluid' to replace the oil should be oil or gas.
OK ???
Fine...
This is not so simple. Because the oil is usually in reservoir under pressure and the first thing that will happen will simply be a drop of pressure. Imagine you take a wet sponge, you pack it in a plastic bag, put a wooden board with stones on top. Now, if you pierce with a needle the bag to reach the sponge, the water will go out but it will not be replaced by air. Simple experiment which brings us to the next.
There are different way for the oil to be produced : the oil can be 'pushed' out by the water, the gas or even by the reservoir compaction (A bit like the sponge getting flat once the water is out)
So, you understand now that it is a system where the air is not entering directly in line.
Once a reservoir is not exploited anymore, there is still oil inside, same as the sponge will never be completly dry even if you press it strongly. This percentage of oil depends but it is usually between 30 to 70%. We leave a lot of oil in the ground ! The remaining space within the pores will be containing water or gas but it will NEVER content air.
I hope this was clear.

Answer 2

*..There are no vast, empty spaces left when crude oil is extracted from deep underground.

*..Permeable rocks contain tiny pores that allow fluids like water, oil and gas to filter through.

*..Impermeable rocks are solid and don't let fluids pass through.

Here's a bit more info for you.

*..This is what happens in petroleum formations deep under ground:-
*..The crude oil, gas and water are contained within the pores of the rock.
*..While the oil and gas were forming in the rock beds millions of years ago,, it also tended to move (migrate) in an upward direction, generally driven by water. This takes place from the source bed rocks through permeable porous rocks.
*..Water, Oil & Gas move under the same forces, but in slightly different directions, Gas is much less dense than oil, and oil is less dense than water, so there is tendency for the gas and oil to move upwards through the water.

*..This upward movement of the components (water, oil and gas) continues, until they become trapped, Natural gas at the top of course, then oil, and the water underneath.
*.. They become trapped under an impermeable layer (or Cap Rock). It then flows along under this impermeable cap layer, until it reaches a position from which it cannot move any further, and becomes trapped.
Migration continues and the Oil and Gas build up pressure under the cap rock. Oil and gas may also be trapped by another formation like a fault, which has a non-permeable surface.
*..When the formation is discovered by the Geologists, a well is drilled and the 'Down-hole' pressure lifts the oil and gas to the surface. If it's a low pressure formation, other methods are used to bring up the oil.. Gas lift systems, Down-hole pumping units, Water flood systems..etc.
*..When a well is'Dead', it begins to produce far too much water and is 'Shut-in'. Surveys are carried out to decide whether or not it can be re-activated by a variety of methods which are mentioned above.

(There's a huge amount of information available on this subject with which I've been associated for many years. A well that produces crude oil and gas, the gas is called 'Associated gas', if it's a gas only well, it's called Non-associated gas).

(Someone mentioned AIR being in the formation.. Not so! air down there where at times, temperatures can be very high and, if air was produced with the other hydrocarbons, it would be highly dangerous)
.....

Answer 3

Oil is found inside pore spaces of rocks, it is not sitting in giant underground lakes. I believe water is often pumped into the reservoir rock as oil is removed...

You'll probably get a better answer soon...

edit:
Yes, but the space was already in the rock. Oil is removed from porous rocks like sandstone of which a significant portion of their volume is pore space. The rock itself is full of holes -- the oil migrates up through the rock until it reaches an impermeable barrier (such as an overlaying layer of shale), then the oil accumulates in the pore spaces of the porous rock creating an oil reservoir.

Answer 4

NO NO it is naturally replaced with salt water .