Dolomitization and Carbonate Reservoir Formation

The potential of carbonate reservoirs is largely controlled by sedimentary environment.The carbonate reservoirs however,are affected by dolomitization,either directly or indirectly by diageneses,such as dissolutions and fractures.Dolomitization can change the carbonate reservoir quality.Also,five situations are involved: the dissolution of dolomitizing fluids,the mole-to-mole or the volume-to-volume replacement of Ca2+ by Mg2+,over-dolomitization by excess fluids,and the enhancement of permeability by dolomitization.In a more indirect way,the porosity or permeability are also enlarged when selective dissolution happens after partly dolomitization.And the formed dolomites are thought apt to resist mechanical and chemical compaction so as to preserve porosities,and apt to develop fractures than the corresponding limestones.Basically,sedimentary conditions are important.It is revealed that the dolomitization is prerequisite,and constructive diageneses other than dolomitization are Key to the formation of effective reservoirs.