Page 124 - Petroleum Geology

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with the uncemented casing in a cable-tool hole that enters an artesian aquifer,
so petroleum reservoirs of different energies can communicate with each
other behind casing if it is not sealed. The production string is not necessarily
cemented to the surface, but to a level comfortably within the protective
casing. The reservoirs will be produced through perforations in the casing
made by bullets or shaped charges fired from a gun lowered into the hole on
a cable.
Geological considerations enter into the casing programmes of all wells.
Such considerations are particularly important in exploratory holes drilled