Oil and Gas?

Question

When we take oil and gas out of the ground - what happens to the void that is left behind? Surely if we keep taking it out there will be massive holes in the earths structure?

Answer 1

oil is found in traps, which are either "structural" in nature, like an oil trap generated by faults-where the trap was made by the physical movement of the earth, upthrusting, faulting, etc. a second type of oil trap is said to be "stratigraphic" in nature, like ancient sand dunes, overlayed by a layer of shale, which is impermeable. the basic principal of a oil trap is the water drives the oil up against and impermeable barrier until it is trapped. then people drill into these reservoirs.

in addition most oil traps are very thin, only 10-100 feet in nature, although in the middle east they can be over 1000 feet thick. so compared to the thousand and sometimes 10000 of thousands feet of overburden, geologically the oil reservoirs are a very, very, very small part of the earths crust, thus in general there is no danger of "collapse" if oil is removed.



well oil is lighter than water as far as its density, and oil and water are said to be immiscible, that is they do not mix, so when you remove the oil, typically water just moves in naturally to fill the void left by the oil, through normal reservoir water drive mechanics. in most fields ,unless you have a very unusual field/reservoir that is virtually all oil. the oil will be on top of the water in the reservoir where it is 'trapped"., and since the gas is lighter than the oil, it will sit at the very tip top of the reservoir, where an impermeable barrier will prevent its migration. so a typical reservoir will have water at the bottom, then oil, and if there is also gas present then gas on top of the oil. if the reservoir only has water and gas then the gas will be on top of the water.

very little of the reservoir is actually void space and contains fluid, be it water or oil (or gas), typically its under 25 %, and in most cases only 15 % of the reservoir is void space. this void space is called the "porosity" of of the reservoir. porosity is , the space per unit volume that can be filled with water, oil, or gas and is not actually physical 'rock" matrix. now some rock has effectively zero porosity, or void space in it, and this type of rock, which is said to be very dense typically does not make a good oil reservoir and you would get little or no oil out of its due to the very low porosity. typically if a reservoir has a porosity of under 5 % it wont produce enough oil to be commercial.

now the rock of the reservoir in addition to porosity, must be permeable if it contains hydrocarbons. permeability measures the ease at which oil will move through the reservoir. so not only must the reservoir be 'porous"- that is have a certain void space percentage in the rock matrix, it must have permeable to produce oil. some oil reservoirs contain a lot of shale among the reservoir rock which is typically sand, or limestone, or some complex carbonate rock structure, and this shale will typically make the reservoir less permeable. you can improve the permeability of reservoir by fracturing it with chemicals or high pressure water sometimes but not all reservoirs respond to fracing. it depends on the rock.

in some cases to maintain pressure, IF THE RESERVOIR IS LARGE, they will inject water (or gas) back into the formation, which helps maintains the integrity of the geological structure with respect to the pressure and support the overburden geological structures. but for small reservoirs this is not done typically due to the costs associated with reinjecting water, or gas. so in the usa for stratigraphic traps, which tend to be very small, relatively speaking structures, nothing is done like pumping water or gas into the reservoir after the oil is removed, as the rock matrix will still be strong enough to support the overburden formations, and typically more water will move into fill these void space of the rock matrix and you will just see a minor loss of reservoir pressure.

the deepest wells they are drilling these days are around 30,000 feet if you are interested. about as deep as mt everest is tall.

people who tell you rock does not have void space in the interstitial areas of the rock matrix do not know what they are talking about. without this void space you couldnt produce oil!!!

Answer 2

Oil and gas are not just sitting around in big holes - most oil is basically sucked out of porous rock by forcing a mud mixture in which forces the oil out. The rock stays behind, obviously!

Answer 3

Oil unlike coal is not found in the earth but is contained in porouse rock,
Oil when taken out of the earth is refilled with water or a mud mixture.
Coal when taken out of the earth leave a area that is lower than before because coal is a rock that is removed, leaving space and colapsing the earth when it is strip minded.
Oil leaves the earth with a look that the earth has been untouched

Answer 4

oil and gas fill the pores in rocks .. originally, the pores are empty with no filling materials , and for this oil and gas fill them .. when oil and gas are pumped the pores are empty again .. these pores are very small (between the grains composing the rock or the cracks and fractures) .. so no holes or large voids will be left ..
oil doesnt form seas beneath earth !!!

Answer 5

no it is held in porous rock, tightly packed. There are no great voids left. Interesting though, some of the 'empty' rocks are used by companies to store excess gas rather than piping it back to shore ... they can do this as and when the demand arises.

Answer 6

What are some of the problems you see arising in our near future?
The specific concerns are with production control equipment that is located on the seafloor. Older generations of subsea wells had a designed life of 15 to 20 years. Ignoring that lifespan, could become risky from safety and economic perspectives.
Egil Tveit of FMC Technologies,says "We're now entering into a phase where we're maturing the industry,"Tveit said. From the investment side and proactive approach where would you go from here? You can read about the "trouble spots" or address the aging infrastructure. Look up the OTC Conference review and read for your answer or question.

Answer 7

Nope ..they fill in the holes with saw dust...thats why you can never buy saw dust in your local super market any more..the oil companies are using it all up..the real question will be what happen when we run out of saw dust..that stuff doesnt grow on trees you know..rock on dude..keep up the fight..

Answer 8

Some companies are thinking of burying carbon dioxide to fill the void.

Answer 9

Nature is always follow the dharma......Human never follow. So, we no need to worry so much about the nature. Firstly we have to thing our self.

Oil and Gas is given by GOD, it was and is controlled by them.

Answer 10

Yes.