Nothing looks more solid than a rock. Yet, choose the right rock, (a piece of sandstone or limestone) and look at it under a microscope. You will see many tiny openings. Geologists call these tiny rock openings 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 hydrocarbonscan 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. 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.

Oil Primer [[Oil and Gas Reservoirs]] Home