Upper Ordovician Glaciogenic Deposits, Saudi Arabia

Upper Ordovician Glaciogenic Deposits (UOGD) contain significant hydrocarbon reservoirs in North Africa and the Middle East. In Saudi Arabia, the UOGD includes the Zarqa, Sarah (Figure 1), and Hawban Formations (central, north, northwest) and the Sanamah Formation in the southwest; however, in the subsurface, the UOGD is primarily referred to as the Sarah Formation ¹, ².

As part of collaborative efforts with other CPG researchers, we investigated core samples from the Rub’ al Khali Basin and several outcrops in central, northwest, and southwest Saudi Arabia. The results of this effort are published in peer-reviewed journals and presented at various well-known conferences.

Figure 1: Sedimentary facies and ferruginous deposits in the Sarah paleovalley, Saudi Arabia [the source: https://doi.org/10.1038/s41598-023-45563-9].

Highlights of Our Research

Facies Heterogeneity and Paleoenvironments of a Tight Gas Sandstone Reservoir

• This study investigates the facies heterogeneity and paleoenvironments of the glaciogenic Sarah Formation (Hirnantian) in the Rub’ al Khali Basin, a potential tight gas sandstone reservoir ¹, ².
• It integrates core analysis, petrographic thin sections, and spectral gamma-ray (SGR) analyses.
• The paper identifies four facies associations (FAs): fluvial (FA1), glaciofluvial (FA4), glaciolacustrine delta (FA2), and subglacial (FA3), interpreting their depositional environments.
• It characterizes the sandstone composition and textural attributes of these facies.
• The study demonstrates how the integration of facies analysis with SGR responses can further classify lithofacies (e.g., low matrix vs. argillaceous sandstones, diamictites with shales).
• This research provides guidelines for facies identification and prediction of reservoir-quality targets in subsurface tight sandstones.
• Recommendation: Researchers interested in depositional settings, lithofacies characterization, and the application of spectral gamma-ray analysis in glaciogenic tight gas reservoirs should refer to this paper.

Factors Controlling Reservoir Quality of a Tight Sandstone

• This paper examines the factors controlling the reservoir quality of a Paleozoic tight sandstone (Sarah Formation) in the Rub’ al Khali Basin ¹, ³.
• It integrates core descriptions, petrographic studies, and porosity-permeability measurements on samples from six wells.
• The study analyzes four identified facies associations (FAs) and their depositional settings.
• It investigates the mineralogical composition of selected samples using QEMSCAN analysis.
• The paper discusses the influence of depositional facies and diagenetic processes (e.g., compaction, cementation, dissolution) on reservoir properties.
• It highlights potential reservoir quality variations among different facies, expecting the best quality in fluvial sandstones and the poorest in matrix-supported diamictites.
• Recommendation: Researchers interested in understanding the interplay of depositional and diagenetic controls on reservoir quality in Paleozoic tight sandstones should consult this article.

Pore Characteristics of a Tight Gas Sand Reservoir

• This paper provides an in-depth analysis of the pore system of a Saudi Arabian tight gas sand reservoir ⁴.
• It utilizes a comprehensive suite of techniques, including routine core analysis, petrography, SEM, QEMSCAN, µCT, NMR, and electrical resistivity measurements.
• Key findings relate to the identification of hydraulic flow units (HFU) based on porosity-permeability data.
• The study investigates factors contributing to reservoir heterogeneity, such as clay minerals, microfractures, and dissolved minerals, and their impact on pore characteristics.
• It examines the agreement and discrepancies between different porosity measurement methods (helium, NMR, gravimetric) across various lithofacies.
• The paper analyzes NMR T2 profiles to understand pore size distribution (micropores vs. macropores) and correlates NMR permeability with helium permeability.
• Finally, it relates electrical resistivity measurements to porosity and rock types, determining a cementation factor.
• Recommendation: Researchers interested in detailed pore-scale characteristics, petrophysical properties, and methodological comparisons in tight gas sands should consult this paper.

Geochemical Characterization of Glaciogenic Deposits

• This study presents a geochemical characterization of subsurface Upper Ordovician glaciogenic deposits in the Rub’ al Khali Basin ⁵.
• It uses geochemical data to evaluate four facies associations (fluvial, glaciolacustrine, subglacial, glaciofluvial).
• The paper investigates the provenance of the sediments, suggesting a derivation from continental felsic rocks of the Arabian Shield.
• It determines the tectonic setting as a passive margin.
• The study also examines the impact of chemical weathering on different facies.
• It discusses the relationship between geochemical maturity and depositional environments, and the implications for reservoir quality.
• Recommendation: Researchers interested in the provenance, tectonic setting, geochemical characteristics, and weathering history of glaciogenic deposits should select this article.

Sedimentology Framework of Early to Mid Palaeozoic Glaciogenic Deposits

• This book chapter focuses on the sedimentology and sequence stratigraphic framework of Early to Mid Palaeozoic glaciogenic deposits in Saudi Arabia ⁶.
• It describes diamictite and sandstone facies observed in both outcrop and subsurface settings.
• The chapter details the classification of diamictites based on grain abundance and distribution.
• It illustrates the controlling factors on reservoir quality, linking it to depositional environments (e.g., fluvial sandstones with dual porosity) and diagenetic processes (e.g., cementation reducing pore spaces).
• It uses subsurface data from the Rub’ al Khali Basin as an example.
• Recommendation: Researchers interested in the broader sedimentological context and sequence stratigraphy of Paleozoic glaciogenic deposits in Saudi Arabia, with a focus on reservoir quality controls, will find this chapter useful.

Ferruginous Deposits in Glaciogenic Formations

• This paper investigates the characteristics, distribution patterns, and origin of various ferruginous deposits in central Saudi Arabia, predominantly within the Late Ordovician glaciogenic Sarah Formation ⁷.
• It utilizes µXRF and CT scans to analyze the geochemical distribution and morphology of these deposits, including concretions, pipes, and layers.
• The study discusses the mineralogical composition (mainly goethite) and potential sources of iron (weathered Arabian Shield).
• It compares the studied ferruginous deposits with those in fluvial and aeolian settings on Earth and Mars, highlighting the potential influence of the glaciofluvial environment.
• The paper emphasizes the need for further quantitative analysis to refine models for the development of ferruginous deposits.
• Recommendation: Researchers focusing on the diagenesis, geochemistry, and paleoenvironmental significance of iron-rich deposits, particularly in glaciogenic formations, and those interested in comparisons with Martian concretions, should consult this paper.

Iron Oxide and Kaolinite Influence on Low Resistivity Pay Sandstones

• This paper studies iron-bearing structures in Paleozoic sandstones of central Saudi Arabia to understand the phenomenon of low resistivity pay (LRP) zones ⁸.
• It combines field descriptions, petrography, QEMSCAN analysis, and resistivity measurements.
• The study identifies various types of iron-rich concretions and their distribution.
• It analyzes the mineralogy, revealing detrital quartz and feldspar, along with iron oxide (goethite and hematite) and kaolinite cements.
• The paper discusses how the presence and distribution of microporous kaolinite and conductive iron oxides can lead to low resistivity in sandstone reservoirs.
• Recommendation: Researchers investigating the causes of low resistivity pay zones in sandstone reservoirs, particularly the role of iron oxides and clay minerals, should consult this paper.

Cite this post

If you found this post helpful, please consider citing it and the references below:

Alqubalee, A. (2025, April 6). Upper Ordovician Glaciogenic Deposits, Saudi Arabia. https://qubalee.com/posts/2025/04/UOGD/

References

1. Alqubalee, A. (2017). Lithofacies and Petrophysical Characterization of the Late Ordovician Sarah Formation, Rub’Al-Khali Basin, Saudi Arabia. Master Thesis, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia. https://www.proquest.com/dissertations-theses/lithofacies-petrophysical-characterization-late/docview/2867895193/se-2 ↩︎ ↩︎² ↩︎³

2. Alqubalee, A., Abdullatif, O., Babalola, L., Makkawi, M. (2019a). Characteristics of Paleozoic tight gas sandstone reservoir: integration of lithofacies, paleoenvironments, and spectral gamma-ray analyses, Rub’ al Khali Basin, Saudi Arabia. Arab. J. Geosci. 12, 344. https://doi.org/10.1007/s12517-019-4467-0 ↩︎ ↩︎²

3. Alqubalee, A., Babalola, L., Abdullatif, O., Makkawi, M. (2019b). Factors Controlling Reservoir Quality of a Paleozoic Tight Sandstone, Rub’ al Khali Basin, Saudi Arabia. Arab. J. Sci. Eng. 1–19. https://doi.org/10.1007/s13369-019-03885-9 ↩︎

4. Adebayo, A. R., Babalola, L., Hussaini, S. R., Alqubalee, A., & Babu, R. S. (2019). Insight into the pore characteristics of a Saudi Arabian tight gas sand reservoir. Energies, 12(22), 4302. https://doi.org/10.3390/en12224302 ↩︎

5. Alqubalee, A. M., Babalola, L. O., Abdullatif, O. M., & Eltom, H. A. (2021). Geochemical characterization of subsurface upper Ordovician glaciogenic deposits: implications for provenance, tectonic setting, and depositional environments. Arab. J. Sci. Eng, 47(6), 7273-7291. https://doi.org/10.1007/s13369-021-06066-9 ↩︎

6. Alqubalee, A., Abdullatif, O., Babalola, L., Koeshidayatullah, A., Benaafi, M., Babiker, J. (2023a). Glaciogenic tight sand reservoirs in the Arabian Plate: Characteristics of the Upper Ordovician deposits, Saudi Arabia, in: Pre-Cambrian to Paleozoic Petroleum Systems in the Arabian Plate. EAGE Publications. https://www.earthdoc.org/content/books/9789462824911 ↩︎

7. Alqubalee, A., Salisu, A. M., Bello, A. M., Al-Hussaini, A., Al-Ramadan, K. (2023b). Characteristics, distribution, and origin of ferruginous deposits within the Late Ordovician glaciogenic setting of Arabia. Scientific Reports, 13, 18430. https://doi.org/10.1038/s41598-023-45563-9 ↩︎

8. Salisu, A., Alqubalee, A., Bello, A. M., Al-Hussaini, A., Adebayo, A. R., Amao, A., Al-Ramadan, K. (2023c). Impact of Kaolinite and Iron Oxide Cements on Resistivity and Quality of Low Resistivity Pay Sandstones. Marine and Petroleum Geology. https://doi.org/10.1016/j.marpetgeo.2023.106568 ↩︎