It has been proposed that most reservoirs are laid down in a body of water by a long-term process, spanning a variety of depositional environments, in both time and space.
As a result of subsequent physical and chemical reorganization, such as compaction, solution, dolomitization and cementation, the reservoir characteristics are further changed.
Thus, the heterogeneity of reservoirs is, for the most part, dependent upon the depositional environments and subsequent events.