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By the time a carbonate unit has been buried to the depths of most petroleum reservoirs, the significant question is often not "how did the pores originate?" but rather, "why are they still there?" Preservation of porosity, regardless of its origin, is a consequence of one or more of the following mechanisms: (1) minimal burial; (2) reduced burial stress, generally due to overpressured pore fluids; (3) increased framework rigidity, which prevents compaction; (4) exclusion of pore waters by petroleum entry; (5) stable mineralogy; (6) permeability barriers, isolating porous intervals from diagenetic fluids; and (7) pore resurrection, a consequence of the temporary filling of pores with cement that is subsequently removed. Examples from the stratigraphic record demonstrate t at each of these pore-preserving mechanisms may control reservoir quality.
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