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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