Sequence Stratigraphy and Depositional Environment of the Zubair Formation in Rumaila Oilfields, Southern Iraq: Microfacies and Geochemistry

Alsultan, Hamid Ali Ahmed; Awadh, Salih Muhammad; Al-Owaidi, Mohanad R.A.; Al-Khafaji, Amer Jassim

doi:10.46717/igj.54.2b.3ms-2021-08-23

Cited by 7 publications

(8 citation statements)

References 12 publications

(19 reference statements)

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“…Shelly limestone with authigenic quartz indicates a more stable, open marine environment conducive to the preservation of shelly fauna. While the Nasiriya Section has clayey dolomite and shelly dolomite beds, both signify an open marine environment within the platform interior, indicating a continuous or similar depositional setting [16](fig. 3).…”

Section: Discussionmentioning

confidence: 99%

A Comparative Analysis and Environmental Interpretation of the First Cycle of Nfayil Formation in Two Distinct Southern Desert Locations, Iraq

Ajar,

Mahdi

2024

IOP Conf. Ser.: Earth Environ. Sci.

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Nfayil Formation (Middle Miocene) is considered the equivalent of Fatha Formation; it is exposed in the western and southern Desert of Iraq with two members: a carbonate Lower Member that is composed of three cycles of limestone and marlstone intercalation and an Upper clastic Member of sandstone and claystone with thin layers of limestone. It extends from the western to the southern desert with a systematic succession of two or three cycles of lower members each one consisting of an interbedding of soft olive-green marl with medium tough shelly limestone rich with oyster shells. The upper member disappears in many localities due to erosion activity. From the field observation this succession was normally exposed in the southern Desert at the western parts of Al-Muthanna Governorate to the south of Dewaniyah Governorate, while in the eastern part of Al-Muthanna Governorate to the south of Al-Nasiriya Governorate, the beds showed a different lithology and fossil content. The olive-green marl turned to be rusty red with a higher content of fossils, the shelly limestone bed rich with oyster shells became red in colour, rusty and the oyster shells were substituted by pelecypods shells with the same concentration. A microfacies analysis study supported by chemical and X-ray analysis was carried out to predict the depositional environment and deposition circumstances in both sections. The thin section, chemical analysis and X-ray analysis were accomplished at the laboratories of the Iraq Geological Survey. Chemical analyses showed a high ratio of MgO oxide in Nasiriya section compare with Samawa section, that result was supported by X-ray analyses which refer to calcite mineral as the only mineral exists in Samawa beds wile in Nasiriya minerals of dolomite, quartz, feldspar and clay minerals were appeared. Environments extracted from thin section study showed more local fluctuations in sea level in Samawa section.

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Section: Discussionmentioning

confidence: 99%

A Comparative Analysis and Environmental Interpretation of the First Cycle of Nfayil Formation in Two Distinct Southern Desert Locations, Iraq

Ajar,

Mahdi

2024

IOP Conf. Ser.: Earth Environ. Sci.

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“…The lithic fragments are sub-angular to rounded. Dominance of calcareous algae and a lesser proportion of other marine bioclasts indicate a restricted to semi-restricted shallow marine environment (Abd El-Moghny & Afifi, 2022; Al-Ali et al, 2019; Borgomano, 2000; Lucas et al, 2015; Vaziri-Moghaddam et al, 2010). The presence of stylolitic seams (though not prominent) within the limestone may indicate weak compaction during early diagenesis (Bathurst, 1987; Bilal et al, 2022; Fossen, 2010; Rustichelli et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

Petrographic analysis of Oligocene carbonates of Kachchh basin

Patil,

Pundalik,

Pansare

2023

Journal of the Palaeontological Society of India

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The Kachchh basin is located on the northwestern margin of India. The basin consists of a relatively continuous sequence of sediments from the Mesozoic, followed by the Deccan Traps and finally a complete sequence of the Cenozoic sediments. The Cenozoic sediments of Kachchh basin are mainly shallow marine deposits characterised by five formations viz. Matanomadh, Naredi, Harudi, Fulra Limestone and Maniyara Fort Formation. The Maniyara Fort Formation belongs to the Oligocene age. The field and petrographic characteristics of the Oligocene limestones from the Golay river section were studied in order to understand the depositional environment. The petrographic investigation of the carbonate rocks of three members of the Maniyara Fort Formation, namely Lumpy Clay Member, Coral Limestone Member and Bermoti Member provides important information for understanding the depositional facies and diagenetic signatures. The Lumpy Clay Member has shale-siltstones with interbedded limestones, characteristically composed of a significant proportion of detrital grains of quartz and some lithic fragments. The lithic fragments are sub-angular to rounded, which indicates substantial transport. They are also worn down and broken, bear small cracks which are filled by micritic matrix or mud. The presence of stylolitic seams within the limestone (though not significant) along with mud filling is also noticed. The dissolution is not prominent, pointing towards shallow burial of the sediments. Paucity of marine fossils as well as the rarity of foraminifera in the Lumpy Clay Member indicate a restricted to semi-restricted shallow marine environment. The limestones of the Coral Limestone Member are petrographically classified as packstone, wackestone and mudstone. Thus, the environment of deposition seems to have varied from restricted lagoonal to shallow marine environment. The Bermoti Member is characterised by a lens of claystone, which consists of both greyish to yellow coloured claystones interbedded with limestones. The Bermoti limestones are petrographically classified as packstone, wackestone and mudstone assemblage. The limestones were observed to be highly micritised, which indicates open, shallow marine settings. The Maniyara Fort Formation, thus characterised by wackestone-packstone-mudstone facies of carbonates, is interpreted to be part of a carbonate ramp system. The limestones from Maniyara Fort Formation exhibit signatures of marine as well as meteoric diagenesis.

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“…The facies of the Zubair clasts show well-sorted quartz arenite sandstone, poorly sorted quartz arenite sandstone, clayey sandstone that has not been properly sorted, sandy shale, and shale lithofacies (Awadh et al, 2014;Alsultan et al, 2021). As shown in Fig.…”

Section: Zubair Shalementioning

confidence: 95%

Formulating Inhibited Fluids for Stable Drilling Operations into Tanuma and Zubair Shales, Zubair Oilfield, Southern Iraq

Alshibli¹,

Alhaleem²

2022

IGJ

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Tanuma and Zubair formations are known as the most problematic intervals in Zubair Oilfield, and they cause wellbore instability due to possible shale-fluid interaction. It causes a vast loss of time dealing with various downhole problems (e.g., stuck pipe) which leads to an increase in overall well cost for the consequences (e.g., fishing and sidetrack). This paper aims to test shale samples with various laboratory tests for shale evaluation and drilling muds development. Shale's physical properties are described by using a stereomicroscope and the structures are observed with Scanning Electron Microscope. The shale reactivity and behavior are analyzed by using the cation exchange capacity testing and the capillary suction test is utilized for selecting shale inhibitor base. As a result, four drillings muds are formulated with different additives and approved by using the Linear Swelling Meter and the Hot Rolling experiments. Tanuma’s shale is at higher reactivity level, where it is moderate to high active shale than Zubair’s shale, which is at a low to moderately reactive formation. Microfractures and micropores are excited in both formations and potentially in Tanuma’s shale. The shale stability can be achieved by adding 8 % of KCl for Tanuma’s mud and 4% of KCl for Zubair’s mud. The filtration controls are contributed to seal the shale open structures and adding the Poly amino acid hydration suppressant reduced the risk of shale swelling significantly. The results can be used for designing drilling mud to reduce shale instability issues and the cost.

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Sequence Stratigraphy and Depositional Environment of the Zubair Formation in Rumaila Oilfields, Southern Iraq: Microfacies and Geochemistry

Cited by 7 publications

References 12 publications

A Comparative Analysis and Environmental Interpretation of the First Cycle of Nfayil Formation in Two Distinct Southern Desert Locations, Iraq

A Comparative Analysis and Environmental Interpretation of the First Cycle of Nfayil Formation in Two Distinct Southern Desert Locations, Iraq

Petrographic analysis of Oligocene carbonates of Kachchh basin

Formulating Inhibited Fluids for Stable Drilling Operations into Tanuma and Zubair Shales, Zubair Oilfield, Southern Iraq

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