I would have to guess no.. I don't think they could release the oil
quick enough to have it 'collapse'.. It's the water and earth above the
oil pocket that keeps it pressurized, so as the oil is taken from the
pocket, the pocket gets smaller..
The short answer is "YES", but an oil deposit is not typically a cave. It is
typically ocean bottom material that is permeated
with crude oil. It is pressurized by the gravity of the bottom mass above it. As
the oil is withdrawn over time, the oil pressure
reduces, as this permeated material compresses. The length of time this takes
depends not only the size of the field, but the
compressibility of the geology. Very often older fields no longer producing what
they once did are repressurized by injecting high
pressure water into the field in order to increase field production.
Not a cave, it's porous(or not so porous) rock. Frequently, water
displaces the oil, just depends. But subsidence CAN happen in oil
fields, parts of Long Beach are a lot lower than they were before they
started pumping early in the 1900s. 20 feet was the amount bandied
about at the shipyard when I was there.
Harris County, Texas, (Houston) has had major subsidence problems,
particularly in the southern part, and down into Galveston County. Mainly
because of ground water pumping.
Found GeoJournal article ("only" $34 for a PDF) online:
Land subsidence caused by ground water withdrawal in urban areas
Thomas L. Holzer1 and A. Ivan Johnson2
Abstract: At least eight urban areas in the world have encountered
significant economic impact from land subsidence caused by pumping of
ground water from unconsolidated sediment. The areas, most of which
are coastal, include Bangkok, Houston, Mexico City, Osaka, San Jose,
Shanghai, Tokyo, and Venice. Flooding related to decreased ground
elevation is the principal adverse effect of the subsidence. Lesser
effects include regional tilting, well-casing failures,
ldquorisingrdquo buildings, and ground failure or rupture. Subsidence
of most of these urban areas began before the phenomenon was
discovered and understood. Thus, the subsidence problems were
unanticipated. Methods to arrest subsidence typically have included
control of ground water pumping and development of surface water to
offset the reductions of ground water pumping. Ground water recharge
has also been practiced. Areas threatened by flooding have been
protected by extensive networks of dikes and sea walls, locks, and
pumping stations to remove storm runoff.
EXPLETIVE: A balm, usually applied verbally in hindsight,
which somehow eases those pains and indignities following
Yeah, they sucked a lot of water out of there for a long time. That area
used to be great, The Springs. We used to go rent horses at a place there
and ride all over around there. Now it's landlocked by houses, but they did
manage to preserve quite a bit of it, probably because it was too unstable
to do anything else with.
visit my blog at http://cabgbypasssurgery.com
The difference between settlement from drawing down aquifer and an oil
producing formation is the depth that the fluid is drawn from.
Generally, water aquifers are much closer to the surface than the
5000' of the formation in question in the Gulf.
short answer - yes - just look at long beach CA, for example, where as they
drill the land subsides - solution - pump water back in as you take oil out.
so, as the cavity of oil is emptied, they will probably put water in - if
for no other reason so they can get the oil out by displacing it with water.
but if they did nothing, the cavity would be unsupported and might well
I'm thinking water tends to take the place of oil. It may be injected into the
get the oil out. I'm not an oil patch type.
I seem to remember the SPR (stategic petroleum reserve) needs water to draw down
reserves. I can't find a cite tonight so I may be wrong on that.
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller
(PDT) typed in rec.crafts.metalworking the following:
Think of a sponge. That is to say, there isn't a large hollow
space full of oil, but a lot of little holes in a porous substance.
"Picture if you will..." a balloon holding a saturated sponge
underneath a brick (the balloon simulates non-permeable strata, the
brick all the strata on top; the ten thousand plus feet of "dirt"
between the ocean bottom and the oil deposit.) Drill a hole through
the brick, stick a soda straw in, and the oil "squirts" out.
Eventually, the pressure between the brick on top and the sponge
equalizes - the sponge gets "mushed flat". The well goes out of
production. The field is "played out."
Yes, there will be some subsidence - happens where ever there is
fluid (gas, oil or water) being removed from strata, and not being
replaced. In some areas, water seeps in to replace the oil,
percolating "up" as the oil is drawn off.
No. It collapses due to the weight of the earth over the "played
out oil field". Someone from the oil field can probably tell you how
much oil is left after a field "plays" out - I've hear 80% gets left
in some areas.
But it is not like there is a bubble two miles down full of oil,
so much as two miles down, there is a "sponge" full of oil. And
pumping the oil out "compromises" the ability of the sponge to hold
the top layers "up".
You hang out with geologists and date a reference librarian, it is
amazing what you learn.
We will drink no whiskey before its nine.
The response is rather complicated but essentially there is no large
cavern down there that was filled with oil and is now dry. What does
exist is a porous, usually some sort of rock, area which is now
depleted of the liquid that it once contained.. Several techniques
have been used. Forget it, leave it alone... sometimes results in
sinkage of the surface regions just as taking water from an aquifer
may. Injection ... water is often injected into the reservoir which
does two things. It re-loads the structure with liquid and, two, it
may increase pressure (that is rapidly depleting) in the structure
being produced from.
In most cases, a depleted well is simply permanently plugged with
concrete and abandoned.
John D. Slocomb
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.