uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Impact of structural setting on diagenesis of fluvial and tidal sandstones: The Bahi Formation, Upper Cretaceous, NW Sirt Basin, North Central Libya
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
2012 (English)In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 38, no 1, 211-231 p.Article in journal (Refereed) Published
Abstract [en]

This petrographic, mineral chemical, fluid inclusion, and stable isotopic study shows that the distribution of diagenetic modifications and their influence on reservoir quality and heterogeneity in tidal and fluvial sandstones of the Upper Cretaceous Bahi Sandstones in the rift Sirt Basin, NW Libya varies systematically along a series of closely-spaced, dominantly normal faults between the basin margin and more basinward-located areas. Shallow eogenetic modifications resulting from the percolation of meteoric waters, include infiltration of grain coating clays, kaolinitization of detrital silicates, and cementation by dolomite and K-feldspar overgrowths. Mesogenetic alterations (>70 °C, >2 km) include feldspar albitization, illitization of infiltrated clay and kaolinite, conversion of kaolinite into dickite, and cementation by quartz overgrowths (T h 112 °C-134 °C), barite (T h 145 °C-158 °C) and Fe-carbonates. The restriction of barite and Fe-carbonate cements to the basinward-located sandstones suggests formation by hydrothermal fluids along the faults. Extensive feldspar dissolution and formation of moldic pores in sandstones from the basin margin were probably caused by deep percolation of meteoric waters. Results from this study regarding the structural control on the spatial distribution of diagenetic alterations have implications for constraining the flux of pore fluids and, by extension, reservoir quality in analogous epicratonic rift basins.

Place, publisher, year, edition, pages
2012. Vol. 38, no 1, 211-231 p.
Keyword [en]
Diagenesis, Hydrothermal fluids, Libya, Reservoir quality, Sandstone, Sirt Basin, Structural setting, Barite, Cementing (shafts), Cements, Chemical modification, Feldspar, Kaolinite, Mineralogy, Quartz, Sedimentology, Silicates, Solvents, Structural dynamics, Cretaceous, hydrocarbon reservoir, hydrothermal fluid, structural control, Libyan Arab Jamahiriya, Sirte Basin
National Category
Earth and Related Environmental Sciences
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
URN: urn:nbn:se:uu:diva-184894DOI: 10.1016/j.marpetgeo.2011.05.006ISI: 000310668100016OAI: oai:DiVA.org:uu-184894DiVA: diva2:570913
Available from: 2012-11-20 Created: 2012-11-15 Last updated: 2017-12-07
In thesis
1. Parameters Controlling Distribution of Diagenetic Alterations within Fluvial and Shallow Marine Sandstone Reservoirs: Evidence from the Libyan Basins
Open this publication in new window or tab >>Parameters Controlling Distribution of Diagenetic Alterations within Fluvial and Shallow Marine Sandstone Reservoirs: Evidence from the Libyan Basins
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis demonstrates that geological setting, depositional facies, open system flux of hot basinal brines and descending of shallow waters have a strong impact on the distribution of the diagenetic alterations within continental and paralic/shallow marine sandstones which in turn control the quality and heterogeneities of the reservoirs.

Geological setting controls the mineralogical and textural maturity of sandstone, whereas depositional facies control the pore water chemistry (marine, brackish or meteoric), sedimentary texture and sand body geometry. Eogenetic alterations in the fluvial deposits are dominated by precipitation of infiltrated clays, kaolinitization of detrital silicates, whereas the shallow marine deposits are dominated by precipitation of early calcite and kaolinite. Conversely mesogenetic alterations are dominated by clay minerals transformation, quartz overgrowths and Ferroan- carbonates, barite and anhydrite. Flux of hot basinal brines is evidenced by precipitation of mesogenetic minerals that lack of internal sources (e.g. barite, anhydrite and ferroan carbonate cements), which is evidenced by: (1) restricted occurrence of these minerals in downthrown blocks. (2) The high fluid inclusion homogenization temperatures (Th) of quartz overgrowths (Th > 110-139°C), and carbonate cements (T > 80-140°C), which also have light δ18OV-PDB(-17.6‰ to -6.7‰). Flux of hot basinal brines is further evidenced by occurrence of saddle Fe-dolomite along stylolites. Fluid inclusion microthermometry further revealed a dramatic shift in pore- water chemistry from NaCl dominated brines during precipitation of quartz overgrowths to NaCl-CaCl2 dominated brines during cementation by Fe-dolomite. Presence of mixed brine (NaCl+CaCl2) systems in the fluid inclusions suggests flux of descending waters, which have circulated in the overlying carbonate-evaporite successions. The restricted occurrence of oil- filled inclusion to quartz overgrowths and methane to Fe-carbonate cements suggest migration of oil during precipitation by quartz and migration of methane during precipitation by Fe- carbonate cements. The extensive mesogenetic cements in the down thrown blocks is attributed to flux of basinal brines along deep seated faults, i.e. open system diagenesis.

Integration of fluid inclusion microthermometry, isotopes, Raman spectrometry and thermal tectonic evolution of basins are essential techniques for unraveling the evolution of basinal fluids, cementation conditions and relative timing of hydrocarbons migration.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 62 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1375
Keyword
Diagenesis, Structural setting, Depositional facies, Basin thermal history, Ther- mal/Hot basinal brines, Fluid inclusions, Raman Spectrometry, Stylolites, Hydro-carbon migration
National Category
Geology
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-284581 (URN)978-91-554-9581-7 (ISBN)
Public defence
2016-06-14, Hambergsalen, Villavägen 16, Uppsala, 14:00 (English)
Opponent
Supervisors
Note

Errata: Felaktigt disputationsdatum på spikbladet.

Available from: 2016-05-20 Created: 2016-04-18 Last updated: 2016-06-15Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Khalifa, MuftahMorad, Sadoon

Search in DiVA

By author/editor
Khalifa, MuftahMorad, Sadoon
By organisation
Solid Earth Geology
In the same journal
Marine and Petroleum Geology
Earth and Related Environmental Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 454 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf