Characteristics
of Reservoir Rocks
Nothing looks more
solid that a rock. Yet, if you choose a piece of sandstone or
linestone and look at it under a microscope you will see many
tiny openings. Geologists call these tiny rock openings pores.
The diagram to the
left shows open spaces in a rock called pores.
A rock with pores is
referred to as porous. This means it has tiny holes through which
oil may flow. Reservoir rocks must be porous, because hydrocarbons
can occur only in pores.
A reservoir rock is
also permeable. That means its pores are connected. If hydrocarbons
are in the pores of a rock, they must be able to move out of
them. The arrows in the diagram to the
right shows how the pores can be connected.
Unless hydrocarbons
can move from pore to pore, they remain locked in place, unable
to flow into a well. A suitable reservoir rock must therefore
be porous, permeable, and contain enough hydrocarbons to make
it economically feasible for the operating company to drill for
and produce them.
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