Sedimentology
Umid Kakemem; Mohammad Adabi; Ehsan Dehyadegari
Abstract
Depositional texture, sedimentary structure and present fauna led to characterize twelve carbonate- evaporate facies. These facies were classified in three facies belts including tidal flat, lagoon and shoal. Developpment of tidal zones together with evaporate deposits and thrombolite facies (signs to ...
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Depositional texture, sedimentary structure and present fauna led to characterize twelve carbonate- evaporate facies. These facies were classified in three facies belts including tidal flat, lagoon and shoal. Developpment of tidal zones together with evaporate deposits and thrombolite facies (signs to a shallow depositional environment), the absence of continuous reef‐frame builders, high production of carbonate mud, absents of calciturbidite, tempestites deposits and slump structures are evidences for a homoclinal carbonate ramp setting. The facies based on petrophysical characteristics which is the results of depositional texture and diagenesis are classified in seven reservoir rock types. In which, the first rock type (RT1) has weak reservoir property and toward RT7 reservoir quality will increase. Facies variation related to sea level fluctuations led to subdivide the whole strata into two 3rd order sequences. Facies stacking patterns in the sequences characterized by subtidal facies (lagoon and shoal) tend to have the most reservoir quality that covered by evaporative (Mf1) and peritidal facies (Mf2 to Mf4) with low-reservoir quality. The most reservoir quality in both K1 and K2 reservoir zones is coincident with late TST, maximum flooding surface (mfs) and late HST in identified depositional sequences which is settled in high-energy shoal facies intervals.
Sedimentology
Yazdan Golestan; Umid Kakemem; Mohammad Adabi; E. Dehyadegari
Abstract
Carbonate-evaporate succession with siliciclastic sediments and mixed siliciclastic carbonate deposits of Asmari-Pabdeh reservoir in Karanj Oil Field with Oligo-Miocene in age was studied to determine diagenesis, microfacies and original carbonate mineralogy. Micritization, dissolution, compaction, neomorphism, ...
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Carbonate-evaporate succession with siliciclastic sediments and mixed siliciclastic carbonate deposits of Asmari-Pabdeh reservoir in Karanj Oil Field with Oligo-Miocene in age was studied to determine diagenesis, microfacies and original carbonate mineralogy. Micritization, dissolution, compaction, neomorphism, cementation and dolomitization are the main diagenesis processes that effect Asmari-Pabdeh successions. Petrographic studies led to identification of three types of dolomite such as dolomicrite, dolomicrosparite and dolosparite, in which dolomicrosparite and particulary dolospatite caused increase in reservoir quality. Eleven carbonate-evaporate microfacies were identified. These deposited in four major environments comprises of tidal flat, lagoon, carbonate shoal and open marine. Sedimentary environment of the Asmari Formation recognized as a homoclinal ramp. Diagenetic studies reveal impact of marine, meteoric and burial diagenesis on the deposits. Geochemistry of minor and major elements reveal original aragonite mineralogy for carbonates of the Asmari Formation. The high Sr/Mn and Sr/Ca and minor amounts of manganese implying close diagenetic system with low Water/Rock interaction for the Asmari Formation succession.
Sedimentology
Umid Kakemem; Mohammad Adabi; Bahman Gudarzi
Abstract
Investigating of dolomitization and its effects on reservoir quality of the Upper Dalan Formation with Permian-Triassic in age is the aim of this study. In this section, the Upper Dalan Formation consists of carbonates and evaporite rocks with a thickness of 265m. Eleven carbonate- evaporate microfacies ...
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Investigating of dolomitization and its effects on reservoir quality of the Upper Dalan Formation with Permian-Triassic in age is the aim of this study. In this section, the Upper Dalan Formation consists of carbonates and evaporite rocks with a thickness of 265m. Eleven carbonate- evaporate microfacies have been distinguished on the basis of depositional textures, petrographic analysis and present fauna. These microfacies were deposited in three facies belts including tidal flat, lagoon and carbonate shoal. Absents of turbidite (calciturbidite) and tempesties deposits, slump structures, large barrier reef, widespread tidal flat and lagoonal facies with aboundent of mud matrix indicated that depositional setting of this interval was a homoclinal carbonate ramp. Based on petrographic studies, 4 types of dolomite including dolomicrite, dolomicrosparite, dolosparite and dolomite cement are recognized. Porosity and permeability data in varies dolomites reveals that in most dolomite the amount of permeability is not directly related to whole porosity, but depends mainly on the amount of connected porosities through bottleneck holes and is associated with increasing in dolomite crystal sizes. Therefore, from the early stage of dolomitization in the form of dolomicrite toward increasing in the rate of dolomitization with larger crystal size and with the form of subhedral and euhedral crystals, the reservoir properties had a high visible improvement. Ultimately, by persisting of dolomitization and growth of dolomite crystals toward each other and disappearance of bottleneck holes and creation of dolomite cements, reservoir properties destroyed. Dolomitization increased reservoir quality in grain dominated dolo-packstones with planner crystal texture.
