Impact of depositional and diagenetic controls on reservoir quality of syn-rift sedimentary systems: An example from Oligocene-Miocene Al Wajh Formation, northwest Saudi Arabia

• Published in: Sedimentary geology 2023-03, Vol.446, p.106342, Article 106342
• Main Authors: Bello, Abdulwahab Muhammad, Butt, Muhammad Naveed, Hussain, Arif, Amao, Abduljamiu O., Olariu, Cornel, Koeshidayatullah, Ardiansyah I., Malik, Muhammad H., Al-Hashem, Murtada, Al-Ramadan, Khalid
• Format: Article
• Language: English
• Subjects: Al Wajh Formation; Clay minerals; Depositional characteristics; Diagenesis; Reservoir quality; Rift sediments
• ISSN: 0037-0738; 1879-0968
• DOI: 10.1016/j.sedgeo.2023.106342

Tertiary, syn-rift clastic reservoirs offer a unique opportunity to investigate the pivotal role of depositional and early diagenetic controls on reservoir quality. The Al Wajh Formation is a vital exploration target for petroleum in the Red Sea, and is characterized by early, near-surface diagenetic signatures. An integrated petrographic-mineralogical study is conducted to assess the role of depositional factors (e.g., sand grain size and clay matrix) and early diagenetic overprints on reservoir quality. The Al Wajh sandstones are primarily subarkose and lithic arkose, deposited in alluvial fan, braided fluvial, and nearshore environments. Braided fluvial sandstones of the formation have the best quality reservoirs (average porosity: 23.2 %; average permeability: 3025 mD) because of medium to coarse grain size and small proportion of clay matrix, whereas the nearshore sandstones form reservoirs of far lower quality (average porosity: 12.6 %; average permeability: 486 mD) owing to predominantly finer grain size and higher proportion of clay matrix. Clay volume between 10 and 20 % generally reduces the reservoir properties to