So the search for conventional oil
is really a search for these special oil traps
and special conditions.
Now, when did this start happening?
Well, oil has been known for a long time.
In more recent times,
oil was used during the 19th century,
primarily as a lubricant for wagon wheels,
but it was not used as an energy source
because it was very limited in supply.
The only place that people knew where they could get oil from
were what-were localities called natural oil seeps.
These are places where cracks or fractures
tap into an oil reserve underground
so the oil is able to migrate up and bubble out
at the surface of the earth.
You can actually see
some of these natural oil seeps today,
for example, the La Brea Tar Bits
that occur in a park in California
near the city of Los Angeles.
You can go there, look at the ground,
and watch oil actually bubbling out at the surface.
But that was not enough of a supply,
so in the mid 19th century
a group of investors from the eastern United States
decided to see if they could figure out how to drill a well,
like a water well,
only into an oil reserve,
and collect oil in sufficient quantities
to economically produce it and use it
as a-as a heating source or as a lighting source.
One of the reasons there was a lot of demand
and a lot of interest in this
was that the predominant lighting source
at the time was whale oil,
and whales were being hunted to extinction,
so the supply of whale oil was pretty much being overused.
Well, to make a long story short,
in 1859 these investors hired a guy named Edwin Drake,
he drilled a well in Pennsylvania, it struck oil,
and so to speak, the rest is history.
Basically, beginning in 1859
the world began to utilize oil
in vast quantities, and the oil age began.
These days, finding oil reserves
is a much more complicated and expensive process.
All the easy oil has been found.
To find oil reserves today
requires primarily the use of a technique
called seismic reflection profiling.
Specifically, geologists generate a source of energy
that sends artificial earthquakes,
basically vibrations, into the earth.
Those vibrations bounce off the layers of strata underground
come back up to the surface
where they are recorded by small seismographs.
A computer is able to take the data,
and by measuring the travel time
for the energy to go down and come back up,
can produce an artificial image of what's underground.
In effect, it's like an x-ray of the interior of the earth.
This method can be used on land,
typically by using big trucks that have a metal plate
that presses against the surface
and transmit a low-frequency vibration into the earth,
or it can be done out in the ocean
where a boat tows what's called an air gun
that sends a pulse of high-pressure air
into the water
that generates a vibration that passes through the water
into the sediment below
and down into the rock beneath that
and then gets-gets, uh, returns to the surface
and is recorded by seismographs that are towed behind the ship.
The technique is very sophisticated, very complicated.
Now it can be done in three dimensions,
so you can create cubes of information underground.
But basically, as you can see in this simple reflection profile,
the layers of strata show up as different bands,
and-and you can see their shapes
and recognize potential traps underground,
because the process of drilling is so expensive these days,
millions and millions of dollars to drill a single hole,
that oil companies do not want to drill
without being pretty sure
that they're going to strike a significant reserve underground.
