Depositional and diagenetic controls on deeply-buried Eocene sublacustrine fan reservoirs in the Dongying Depression, Bohai Bay Basin, China. (April 2017)

• Record Type: Journal Article
• Authors: Ma, Benben; Cao, Yingchang; Eriksson, Kenneth A.; Jia, Yancong; Gill, Benjamin C.
• Is Part Of: Marine and petroleum geology. Volume 82(2017)
• Page Start: 297
• Page End: 317
• Publication Date: 2017-04
• Subjects: Depositional lithofacies -- Diagenetic history -- Reservoir quality -- Eocene -- Bohai Bay Basin; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2017.02.014
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: This paper investigates the reservoir potential of deeply-buried Eocene sublacustrine fan sandstones in the Bohai Bay Basin, China by evaluating the link between depositional lithofacies that controlled primary sediment compositions, and diagenetic processes that involved dissolution, precipitation and transformation of minerals. This petrographic, mineralogical, and geochemical study recognizes a complex diagenetic history which reflects both the depositional and burial history of the sandstones. Eogenetic alterations of the sandstones include: 1) mechanical compaction; and 2) partial to extensive non-ferroan carbonate and gypsum cementation. Typical mesogenetic alterations include: (1) dissolution of feldspar, non-ferroan carbonate cements, gypsum and anhydrite; (2) precipitation of quartz, kaolinite and ferroan carbonate cements; (3) transformation of smectite and kaolinite to illite and conversion of gypsum to anhydrite. This study demonstrates that: 1) depositional lithofacies critically influenced diagenesis, which resulted in good reservoir quality of the better-sorted, middle-fan, but poor reservoir quality in the inner- and outer-fan lithofacies; 2) formation of secondary porosity was spatially associated with other mineral reactions that caused precipitation of cements within sandstone reservoirs and did not greatly enhance reservoir quality; and 3) oil emplacement during early mesodiagenesis (temperatures > 70 °C) protected reservoirs from cementation and compaction. Highlights: Sublacustrine-fan sandstones in the Eocene Es4 interval are important hydrocarbon reservoirs. Depositional lithofacies critically influenced diagenesis. Formation of secondary porosity was associated with other mineral precipitation and did not enhance reservoir quality. Oil emplacement during early mesodiagenesis protected reservoirs from cementation and compaction.