The dolomitized{open_quotes}O{close_quotes} Limestone in the Barinas basin: A hydrocarbon reservoir in carbonate rocks
Journal Article
·
· AAPG Bulletin
OSTI ID:421032
- Corpoven, S.A. Puerto La Cruz (Venezuela)
- Estudios Geologicos Afrolatin, C.A., Caracas (Venezuela)
The {open_quotes}O{close_quotes} Limestone Member, top of Escandalosa Formation of a Lower to Upper Cretaceous age, is an interval of about 70 feet thick. It represents a coastal facies of caitonate platform; dominated by carbonates of calcarenitic lithologies intercalated with some sandy, glauconitic, calcareous bodies and thin bioturbated shaly intervals. Detailed studies carried out in five cores yield to a new approach and subdivision within this interval based on diagnostic erosive surfaces that may be interpreted as sequence boundaries. Based on sedimentology, trace fossil assemblages and diagenetic events, the milieu of sedimentation varies from foreshore to offshore. Porous dolomite levels occur within the {open_quotes}O{close_quotes} Limestone. This porosity is of intergranular, moldic and vuggy types. Some microfractures are also observed. Subaerial karstification is an alternative hypothesis that can explain the origin of the localized dolomitized vuggy reservoirs. The following sequence of events is suggested: (1) Sedimentation followed by bioturbation, then lithification with a probable replacement of aragonite by calcite, (2) Early dolomitization undergoing the {open_quotes}mixing{close_quote} or {open_quotes}Dorag {close_quotes} Model, (3) Dedolomitization and dissolution generating a moldic porosity enhanced the vuggy forms. This stage may have been influenced by karst processes, (4) Burial diagenesis accompanied by stylolitization and fracturation with pressure-solution effects, and (5) Some levels increase their porosity because of partial dolomitization; in others the vuggy porosity is totally infilled with sparry calcite.
- OSTI ID:
- 421032
- Report Number(s):
- CONF-9609255--
- Journal Information:
- AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 8 Vol. 80; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
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