On Apr 29, 1:47*pm, Larry L wrote:
What makes the oil continue to flow at the spill? * * *I mean it's a
mile deep with tons of pressure on it and the wells I'm used to seeing
all have those little grasshopper pump deals. * *I thought you had to
pump the oil out or force in something else to force the oil out.
If there is so much pressure in the oil field itself that it overcomes
the pressure of the sea then why don't we have natural oil flows all
over the world like magma coming out under pressure in volcanic areas?

Larry L ( who it seems doesn't have a clue how an oil well works )

In simplest terms, the pressure acting on pockets of oil is highly
variable. In some places and at some times it is greater than in
others. Likewise, the thickness, elasticity, friability and various
other characteristics of crustal material surrounding such pockets is
also variable. In some places, at some times, there are natural flows
of "oil" just like there are flows of lava. One might as well ask why
the latter doesn't always flow everywhere all of the time. Then, too,
a "pocket" of petroleum may be an otherwise empty hole (more or less)
or it may be a highly porous material of some sort saturated with
petroleum.....and other substances. In either case, there may be
enormous pressure on the cavity. But the forces applying the pressure
may be very dynamic or entirely static. If dynamic, that is to say
that whatever is creating the pressure is free to move as the
petroleum (or whatever) is pushed out, a rupture is likely to continue
exude oil for some time. If static, unable to continue to apply more
pressure as material is moved out, flow eventually stops.

Think of a piston in a cylinder. If the cylinder is closed at the end
opposite the piston, enormous pressure can be built up as the piston
moves. Put a hole at the end and the pressure is relieved as material
moves through it. Keep moving the piston in, and the pressure keeps
moving material out the other end. Stop the piston's motion and the
flow at the other end eventually stops. If you want the rest of the
stuff in the cylinder you have to pump it out.....or find a way to
make the piston move some more.....not an easy task when we give up
the metaphor in favor of real world dynamics.

Lava flows follow exactly the same rules. They just do so (usually)
on a much grander time scale.

As to forcing something in to force the oil out, that's analogous to
applying pressure to the piston. But as I understand it, that is
usually done indirectly. Water is sometimes pumped into oil fields in
order to raise the level of the oil. This is simply a means of
letting gravity do most of the hard work. Water is denser that
petroleum and will sink to the bottom of whatever vessel contains
both, thus displacing the petroleum upward. Remember that there are
limits to how high fluids can be raised by pumping. At one point or
another the inherent weight of the fluid in a closed column will cause
the fluid at the top to vaporize, essentially creating a vaccuum which
makes it impossible to pull it up any higher. For water, I believe
the limit is something like thirty feet. I don't know what it is for
petroleum, but for the sake of argument, let's suppose it's the same.
In effect this means that the pipe you pump the stuff up with is a
maximum of thirty feet long.....you can't reach any deeper. But the
oil goes down three thousand feet! What do you do? You keep pumping
water in (no maximum depth for pumping the stuff DOWN) and letting it
lift the petroleum to the level of your pipe.

Viola!

giles