[Ayoob]

If you tore the top off an oil reservoir, what would you see on top? Would you be looking at a pool of oil, or would you be looking at a layer of sand?

As you make your way down from the top of the reservoir to the middle, are you going through only liquid oil, or are you going down through a rocky sandy sludgy junky mess?

The reason I ask is on another board a guy that supposedly works in an oilfield said that's what it looks like. He used the analogy that it's like packing crushed ice in a cup and then pouring root beer in on top, then poking a straw in to the bottom.

Is that accurate? Are all oil fields this way? It makes sense... it's just that I've never run across this before.

[MonteQuest]

Oil is contained in porous sedimentary rock, as I understand it.

Reservoir Rocks

[Aaron]

Oil is spun from gold & fairy dust deep in the Earth by Abiotic Gnomes from Russia who worship Tesla's frozen head and hijack airplanes.

[MonteQuest]

I stand corrected.

[rockdoc123]

The reason I ask is on another board a guy that supposedly works in an oilfield said that's what it looks like. He used the analogy that it's like packing crushed ice in a cup and then pouring root beer in on top, then poking a straw in to the bottom.

Is that accurate? Are all oil fields this way? It makes sense... it's just that I've never run across this before.

all I can thinkis that he is talking about tar sands. There are some conventional sandstone reservoirs that are "under compacted" , either they are overpressured or they were never properly cemented. In such a case what you would see at surface when it is produced is a mess of loose sand grains mixed with oil. However, even an undercompacted sandstone reservoir is not going to look like that described by this gentleman. The grains will be in contact under pressure....it is only when the pressure is released (ie. there is a pressure drop from the reservoir to the borehole which allows the oil to produce to surface that you see this sort of "floating" mess described. If you think about it the the describition he gives suggests a material that would have basically zero compressional strength....if so how could it support several thousand feet if not meters of rock material which lies above it? As a quick estimate a reservoir buried at 7000 feet would have an overburden pressure of about 3500 psi (remembering that 14.5 psi is the conditiona at STP). Also try telling this to the people who have to store literally hundreds of thousands of metres of full diameter or slabbed core around the continent....you would not be able to recover any core if the description given were correct.
So if this were liars dice you should declare "bullshit"

[shakespear1]

Rockdoc has basicly described the mechanism that is of importance here. Pressure. The oil undersground is compressed into the pores spaces so if you tore open the Earth in some controlled way, the gases would first start to come out as they are in solution (in general) and at the same time the oil would expand and start to ooze out creating a bubbling lake. IF THIS WAS DONE SLOWWWLLLLYYYYY. BIG IF. Otherwise the rock would expode because the oil would see a sudden drop in pressure and would expand to a larger volume than the pore space in which it is.

When we take cores out of wells the core is able to see a gradual pressure drop as the core comes up to surface. Then the oil/gas start to come out of the rock and you would see a stained core from intervals where you have oil. Even once on surface the oil may still "bleed" out.

Hope that helps a bit :>)))

[khebab]

As you make your way down from the top of the reservoir to the middle, are you going through only liquid oil, or are you going down through a rocky sandy sludgy junky mess?

Nope! even better: fecal pellets from invertebrate animals!

from Kenneth Deffeyes book "Hubbert's Peak" :

Fine grained calcium carbonate mud usually gets consolidated into massive limestones, usually with little or no porosity. . . . . . . .About 10 percent of ancient limestones do have porosity. . . . . . .Most massive and nonporous limestones contain textures made by invertebrate animals that ingest sediment and turn out fecal pellets. Usually the pellets get squished into the mud. Rarely do the fecal pellets themselves form a porous sedimentary rock. . . .I twisted Aramco's collective arm for samples from the supergiant Ghawar field. . . . .Examining the reservoir rock of the world's biggest oil field . . .a small part of the reservoir was dolomite, but most of it turned out to be fecal pellet limestone. I had to go home that evening and explain to my family that the reservoir rock in the world's biggest oil field was made of shit.

src: the oil drum

[Ayoob]

OK. So the oil, under pressure, is inside the rock in the reservoir. It's not a pool of oil that you could go swimming around in if you could stand the 3500PSI pressure. If you were to poke a stick down in the reservoir it wouldn't go anywhere 'cause it's all rock.

[Kingcoal]

As I understand it, hundreds of millions of years ago there was an inland sea covering Ohio, the shores of which bordered Pittsburgh. Over millions of years, biomass in the form of microbes lived, died and sank to the bottom of these costal areas. This biomass sank into the sands at the bottom and was covered with new sands. Over millions of years, this biomass infused sand sank deeper and deeper and began to come under high pressure. Oil and Gas formed from the biomass. I give a location specific explanation because oil can form in many different kinds of source rock.

Wells in western Pa would often spew out this oil/sand/salt water combination after being "shot."

[rockdoc123]

kingcoal....sort of correct. However the biomass you refer to is largely either bacteria, plant material or amorphous organic matter of some other type that is largely contained in mudstones or coals. Marine mudstones tend to be (not always) made up of type II kerogens which are organics formed mainly from marine planktonic material....type I kerogens are very rick petroleum sources and are most often formed in lacustine (lake) environments whereas coals have mostly type III kerogens or humic matter made up of plant matter. the shale or mudstones or coals are subjected to heat during burial and the kerogens are then converted to hydrocarbons. The hydrocarbon is expelled from the shale, mudstone, coal source bed and finds its way into the sandstone or carbonate reservoir via various migration pathways. In some cases this migration can be very short distance in others up to tens or more kilometers.

[basil_hayden]

Luminescent....

[Ayoob]

I'm going to update this one more time because I don't understand the answers so far. My question is: Could you go swimming in the liquid pool of oil found in the reservoir, or would you bang your head on rock while diving in?

Please, somebody, stick a Yes or a No in here. Or a Yes except when... or a No except when...

Seriously, I don't understand the answers unless you feed me one small spoonful at a time.

[MonteQuest]

I'm going to update this one more time because I don't understand the answers so far. My question is: Could you go swimming in the liquid pool of oil found in the reservoir, or would you bang your head on rock while diving in?

Please, somebody, stick a Yes or a No in here. Or a Yes except when... or a No except when...

Seriously, I don't understand the answers unless you feed me one small spoonful at a time.

No, you couldn't go swimming. There is no pool. Oil is found inside "reservoir" rock.

Did you click on the link I provided in my last post?

[khebab]

Could you go swimming in the liquid pool of oil found in the reservoir

No.

or would you bang your head on rock while diving in?

Yes.

[GoIllini]

kingcoal....sort of correct. However the biomass you refer to is largely either bacteria, plant material or amorphous organic matter of some other type that is largely contained in mudstones or coals. Marine mudstones tend to be (not always) made up of type II kerogens which are organics formed mainly from marine planktonic material....type I kerogens are very rick petroleum sources and are most often formed in lacustine (lake) environments whereas coals have mostly type III kerogens or humic matter made up of plant matter. the shale or mudstones or coals are subjected to heat during burial and the kerogens are then converted to hydrocarbons. The hydrocarbon is expelled from the shale, mudstone, coal source bed and finds its way into the sandstone or carbonate reservoir via various migration pathways. In some cases this migration can be very short distance in others up to tens or more kilometers.

So what I'm hearing is that if we get lots of biomass in a freshwater environment, we usually get coal. If we get it in a saltwater environment, we get oil and natural gas. Is that what you're saying?

[rockdoc123]

So what I'm hearing is that if we get lots of biomass in a freshwater environment, we usually get coal. If we get it in a saltwater environment, we get oil and natural gas. Is that what you're saying?

No coal is formed from woody, plant materials. You can have fresh water coals form in restricted lacustrine environments....in river systems (abandoned channels or oxbow lakes) as well as in marginal marine settings in saltwater (eg. estuaries are good places for coals to form). What I am saying is the type of organic material in coals has more oxygen than hydrogen as compared to say organic rich lacustrine layered muds which have more hydrogen than oxygen....hence the coals produce more gas and less oil whereas the opposite is true for the lacustrine organic muds.

Coals generate oil and gas when they are buried deep enough...they just tend to be more gas prone so they aren't thought of as being the best source rocks.

[DesertBear2]

If you tore the top off an oil reservoir, what would you see on top? Would you be looking at a pool of oil, or would you be looking at a layer of sand?

I was a wellsite geologist for many years in the Rocky Mountain area and have seen a lot of oil tests.

No you cannot swim in a pool of oil in most sedimentary environments. Generally, the oil is contained in microscopic pores that comprise 10 to 20% of the rock volume. These pores are interconnected and allow fluids to flow through them at a rate that is controlled by the porosity and permeability.

However, you probably could theoretically swim in some specific limestone reservoirs where large caverns exist. Limestone reservoir rocks have enormous variability but have most of their useful porosity in micro-crystalline interstices. But caverns can and do exist in some specific reservoirs. This is evident when the drill bit suddenly drops 10 feet with a thud. Actual swimming or boating would be limited by lack of headroom as well as the reservoir pressures hee hee.

Another variable is the viscosity of the crude oil. Light sweet crude flows and can be pumped easily. Heavy crude is less desirable and can have a consistency of sludge.

[Caoimhan]

The hydrocarbons on Saturn's moon, Titan, are abiotic.

Given that Titan resembles Earth in so many ways, why is it so hard to believe that hydrocarbons can be formed abiotically on Earth?