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state. The tax was expected to generate about $400 million per
year for California over a ten-year period. The money was slated
for investment in clean, renewable energy, such as solar and
wind power. Other oil-producing states impose a similar tax,
and more than 60 percent of Californians thought Proposition
87 was a good idea when it was first introduced.
But the companies that pump most of the oil in Califor-
nia—Chevron, ExxonMobil, Royal Dutch Shell, and Occidental—
vigorously opposed the law. If Prop 87 passed, the tax would cut
into their profits. So the oil companies spent $100 million to con-
vince voters that Prop 87 was a bad idea. The companies hired
SEARCH TECHNOLOGY
To search for oil, geologists start with simple observations. They study
photographs of Earth’s surface taken from airplanes and satellites.
Certain land formations indicate that oil might be located belowground.
For instance, a bulge on an otherwise flat surface is sometimes an
indication of oil trapped below.
Other methods are more high-tech. The most important of these is seismic
exploration. Seismic waves are vibrations that travel underground. The
waves interact differently with different types of rock. For instance,
seismic waves behave one way when moving through dense rocks and
another way when moving through porous, oil-filled rocks. Scientists
use specialized trucks on land and air guns underwater to create seismic
waves. Other devices analyze the waves as they travel. This analysis tells
scientists when waves are moving through rocks that might contain oil.
Once geologists have located a likely spot to dig for oil, they drill test
wells. They pull up cores, or cylindrical samples of underground layers of
rock. They study the cores to determine whether any rock layers contain
oil and gas. If so, they can then determine the type of oil or gas, how
extensive the deposit is, and how far underground it is.
After the data is collected, geologists use computers to create maps and
models of the underground formations. These images help oil companies
decide whether to develop the site and how to approach the project.
