Dolomitization and its effect on reservoir porosity in the upper member of the Dalan Formation in South Pars Gas Field (Persian Golf)

Category Sedimentology
Group GSI.IR
Location The 24 Symposium of Geosciences
Holding Date 18 August 2007


Dalan(M-U Permian)Formation consist of carbonate facies with intercalation of evoporite beds. This formation covers a wide area in the folded Zagros and The Persisn Golf. It is one of the most important carbonate gas reservoir. Sedimentological studies revealed that reservoir facies were restricted to the upper member of this formation. Petrographical studies indicate that dolomitization process affected this part and increase reservoir properties. Microscopic studies show that 6 types of dolomite in this part of formation:

1.Dolomicrit: fine crystalline, unhedral, unimodal, with lamination, evoporite minerals and fenestral fabric.

2. Dolomicrosparite: fine to medium crystalline, unimodal,formed by recrystalization of dolomicrit.

3.Replacement dolomite: dolomitization sometimes are fabric selective. In some cases only allochems and in other cases matrix are dolomitized even in some parts rock totally are dolomitized.

4. Dolomite in pores: coarse, limpid, euhedral crystals.

5. Dolomite scattered in microsparite: limpid, euhedral to subhedral.

6. Dolomite adjacent stylolites: fine crystalline, euhedral to subhedral, with brown color.

3 dolomitization models in this part includes:Sabkha, Seepage-Reflux and burial model.


tags: QAZVIN