Diagenesis of the Middle Eocene Upper Dammam Subformation, Qatar: Petrographic and isotopic evidence

Holail, Hanafy; Shaaban, Mohamed N.; Mansour, Ahmed S.; Rifai, Rifai I.

doi:10.1007/bf03175450

Cited by 10 publications

(14 citation statements)

References 23 publications

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“…The range of δ 18 O and δ 13 C values for bulk carbonate samples in this study is comparable to those reported for the BUpper Dammam^Formation by Holail et al (2005) for samples from drill wells in SE Qatar (Fig. 17a).…”

Section: Stable Isotopessupporting

confidence: 88%

“…With respect to stable isotopic composition, type 2 dolomite of Holail et al (2005) is similar to both the dolomite of the UER Formation in general and in boreholes 2 and 3 that of the lower portion of the Rus Formation in this study (Figs. 6,7,and 17a).…”

Section: Stable Isotopessupporting

confidence: 67%

“…17a). In the Holail et al (2005) study, δ 18 O values for dolomitic samples ranged between 0‰ and + 3‰, whereas δ 13 C values were more variable and formed distinct groups including Btype 1 dolomite^between − 6‰ and − 10‰ and Btype 2 dolomite^between 0‰ and − 4‰. Similar to calcitic rocks from this study, calcite cements reported by Holail et al (2005) had more negative and variable δ 18 O values (− 10‰ to − 5‰) but δ 13 C values similar to the accompanying dolomites (− 2‰ to − 8‰).…”

Section: Stable Isotopesmentioning

confidence: 99%

“…Studies of the Eocene rocks of Qatar are numerous and focus on hydrology (Eccleston et al 1981;Baalousha 2016), diagenesis Holail et al 2005), lithostratigraphy (Cavelier et al 1970;Abu-Zeid and Boukhary 1984;Abu-Zeid 1991;Boukhary and Alsharhan 1998;Dill et al 2003;Al-Saad 2005), biostratigraphy (Boukhary et al 2011), and structure (Rivers and Larson 2018). Building on these studies, an effort was undertaken to update the understanding of the near-surface stratigraphy of Qatar in light of both the Rivers and Larson (2018) structural study, as well as recently published regional maps of Eocene depositional environments (Tai et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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The depositional history of near-surface Qatar aquifer rocks and its impact on matrix flow and storage properties

et al. 2019

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Carbonates and evaporites of Paleogene age form the shallow-aquifer rocks mantling most of Qatar, including the Paleocene and Lower Eocene Umm er Radhuma Formation and the Lower to Middle Eocene Rus and Dammam Formations. A core-based study was carried out to improve general understanding of the stratigraphic controls on aquifer matrix properties in Qatar. A cumulative total of 377 m of 10-cm-diameter core was recovered from three boreholes in central and northern Qatar, drilled to depths of greater than 120 m. Sedimentological attributes of these rocks were investigated through core and thin-section description, X-ray diffraction-based mineralogical assessment, as well as whole-rock stable isotopic analysis and integrated with interpretation of gamma-ray logs. Stratigraphic correlation of the penetrated intervals was then undertaken using sequence stratigraphic concepts and isotope stratigraphy (δ 13 C trends) in the context of recently published regional paleomaps and structural studies. In the area of Qatar, the Umm er Radhuma Formation and the overlying Traina Member of the Rus Formation were deposited in marine settings of two different basins. These basins, which extended to the south and north of Qatar, respectively, are interpreted to have been separated by a topographic high, the location of which was controlled by the presence of high-angle normal faults. The southern basin was more restricted and was the site of extensive evaporite and clay-rich siliciclastic deposition during early stages of Rus Formation. Similar evaporites and fine siliciclastic deposits are not observed in time-equivalent strata of the northern basin. During subsequent deposition of the Al Khor Member of the Rus Formation, as well as the Dammam Formation, the basins appear to have been interconnected, and fine-grained siliciclastic deposits are interbedded with, but subordinate to, carbonate strata across Qatar. Most rocks recovered for this study are dolomitic, and dolomitic rocks free of other mineral phases tend to have significant porosity (20-50%) and permeability (10-1000 mD). Decreased connectivity, flow, and storage capacity are caused by (1) the presence of gypsum beds and nodules (only southern Qatar, upper Umm er Radhuma Formation, and Rus Formation), (2) the presence of pore-occluding clays (typically palygorskite) to varying degrees in all formations, and (3) the occurrence of diagenetic calcites, most commonly in the Dammam Formation. Aquifer quality of the near-surface rocks of Qatar is in large part a function of their depositional history and is to a degree predictable using reconstruction of basin architecture, as well as sequence stratigraphic concepts.

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Section: Stable Isotopessupporting

confidence: 88%

Section: Stable Isotopessupporting

confidence: 67%

Section: Stable Isotopesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The depositional history of near-surface Qatar aquifer rocks and its impact on matrix flow and storage properties

et al. 2019

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“…Cements precipitated during much deeper burial, involving many 100s -1000s of metres, typically have more negative δ 18 O values, from -5 to -10‰. This is the case with equant calcite cements in Middle Eocene carbonates from Qatar (Holail et al, 2005). Thus the low negative δ 18 O values of the Gialo cements suggest a shallow-burial origin.…”

Section: Non-ferroan Drusy and Syntaxial Overgrowth Calcite Cementsmentioning

confidence: 95%

Impact of Diagenesis on Reservoir Quality in Ramp Carbonates: Gialo Formation (Middle Eocene), Sirt Basin, Libya

Swei¹,

Tucker

2011

Journal of Petroleum Geology

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The reservoir quality of Middle Eocene carbonates in the intracratonic Sirt Basin is strongly influenced by depositional facies and various diagenetic processes. Based on data from core samples and well logs from five boreholes in the Assumood and Sahl gasfields in the subsurface of the north-central Sirt Basin, six major carbonate facies (and fourteen microfacies) are distinguished in the Middle Eocene Gialo Formation (thickness ~1100 ft / 335 m). Wackestonespackstones dominate the Gialo Formation with abundant grains of larger benthic foraminifera, especially nummulites, in a matrix composed mostly of finely comminuted bioclastic material. Sediments were deposited as a mosaic of facies on a broad carbonate ramp in moderateenergy nummulite-packstone banks, with locally restricted back-bank lagoons and fore-bank areas of foraminiferal debris passing to offshore lime mudstones.Marine diagenesis was minor with micritization of bioclasts and rare vadose marine fibrous cements. Sparry calcite cements are ubiquitous and were precipitated during shallow to moderate burial from seawater and/or meteoric water, the latter largely unaffected by surface-pedogenic processes. This is indicated by the fabrics and pre-and post-compaction precipitation of drusy spar and echinoderm overgrowths, and supported by their bright-to-dull luminescence and low negative δ 18 O signatures (-2.68 to -4.16‰ PDB). Some early neomorphic alteration of calcitic bioclasts is suggested by bright CL and marine to low negative δ 18 O values (-1.06 to -3.93‰ PDB). Bioclastic grains have δ 13 C values ranging between 0.76 and 1.19‰ PDB, interpreted as marine signatures. Similar low positive δ 13 C values of the cements (0.9 to 1.05 ‰) indicate a source of carbonate from dissolution of grains and/or seawater/meteoric water, but without any near-surface/soil effects. Dissolution of grains and matrix, notably originally aragonitic grains but also the originally high-Mg calcite nummulites, was a major porosity-enhancing process, and took place from shallow to moderate burial depths. Fractures may locally have increased porosity too.Shallow-water packstones/rudstones containing both primary intergranular and secondary biomouldic porosity have the best reservoir quality and these are concentrated in the upper parts (top ~100 ft / 30 m) of the wells, with porosity-permeability decreasing downwards. This

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Hydrocarbons and Evaporites

Warren

2016

Evaporites

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Diagenesis of the Middle Eocene Upper Dammam Subformation, Qatar: Petrographic and isotopic evidence

Cited by 10 publications

References 23 publications

The depositional history of near-surface Qatar aquifer rocks and its impact on matrix flow and storage properties

The depositional history of near-surface Qatar aquifer rocks and its impact on matrix flow and storage properties

Impact of Diagenesis on Reservoir Quality in Ramp Carbonates: Gialo Formation (Middle Eocene), Sirt Basin, Libya

Hydrocarbons and Evaporites

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