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rock.  If  these  drops  of  oil  encounter  an  impermeable  surface
           through which they cannot flow, they will continue to flow upward
           along the underside of this impermeable sealing rock and collect in
           traps as shown in Figure 3.3. If no traps are encountered, the oil
           droplets will migrate all the way to the surface creating an oil seep.
           Oil seeps (1) are quite common in areas of petroleum potential and
           were  used  by  the  earliest  oil  prospectors  to  identify  drilling
           locations.
                  Oil  reservoirs  in  the  subsurface  in  many  ways  resemble
           inverted  ponds  or  lakes.  Unlike  ponds  and  lakes,  however,
           accumulations  of  hydrocarbons  are  contained  inside  the  pore
           spaces of solid rock.


































             Figure 3.3 - Reservoirs occur in places where fluids tend to
                                        collect




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