Carbonate cementation in the Tithonian Jeanne d’Arc sandstone, Terra Nova Field, Newfoundland: Implications for reservoir quality evolution

• Published in: Sedimentology
• Main Authors: Olanipekun, Babatunde, Azmy, Karem
• Other Authors: Hendry, Jim
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2021
• Subjects: Stratigraphy; Geology; General Earth and Planetary Sciences; General Environmental Science; Newfoundland
• Online Access: http://dx.doi.org/10.1111/sed.12912; https://onlinelibrary.wiley.com/doi/pdf/10.1111/sed.12912; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/sed.12912

Abstract Petrographic and in situ geochemical analyses were carried out on cores of the fluvial sandstone (<50 to >4 mm; sublithic quartz arenite) dominated Tithonian Jeanne d’Arc Formation interval from wells C‐09 and E‐79 of the Terra Nova oilfield to understand diagenetic control on reservoir quality of the formation. Lithic clasts are dominantly carbonates and shales. Successively, early near‐surface dolomite cementation, eogenetic dolomite dissolution, burial calcite cementation and its subsequent dissolution are the major diagenetic events that controlled the reservoir quality of the sandstone. Dolomite cement grades from mostly Fe‐rich (FeCO 3 ca 12 ± 2 normalized mol.%) in the upper part of the formation to Fe‐poor (<0.07 normalized mol.%) in the lower part of the formation in both wells. The dolomite and calcite cements generally have low Sr and Na; enriched Y and low δ 18 O and δ 13 C values relative to typical marine carbonates. Strontium is enriched in the Fe‐poor (higher Mg) dolomite relative to the Fe‐rich phase. Mineral liberation analyses of shale samples reveal common Fe‐chlorite and minor glauconite. Furthermore, considerable amounts of solutes in the early diagenetic pore fluid were likely derived from water—rock interaction with underlying Oxfordian Rankin Formation marine carbonate that was also exposed in the watershed of the study area at the time. Together, these suggest that the dolomites were formed from an early diagenetic bicarbonate‐rich pore fluid of mixed meteoric and seawater origin. The origin and distribution of early dolomite cementation and other successive diagenetic events have a depositional cycle control. Episodic post‐deposition transgression of seawater and/or compactional fluid expulsion from shales into overlying sandstones led to formation of dolomite cement. Subsequent infiltration of organic acid‐charged meteoric‐water into underlying dolomite‐cemented sandstones resulted in early dissolution. This porosity was mostly occluded by re‐precipitation of ...