Petrographical analysis of the diagenesis and reservoir quality of sandstones from the Nordmela and Fruholmen formations. - A study of the Fingerdjupet Sub-Basin in the Barents Sea.

Abstract

The Barents Sea is going to be a key area for future hydrocarbon exploration activities on the Norwegian Continental Shelf in the years ahead. The reservoir quality of the formations native to the Barents Sea will be important knowledge for the oil companies in the future.

The objective of this paper is to determine the diagenetic processes and reservoir quality of the sandy sections of the Nordmela and Fruholmen Formations of the Realgrunnen Sub-Group in the Fingerdjupet Sub-Basin of the Barents Sea. A Petrographic analysis of thin sections taken from core samples has formed the basis of this study. Optical microscopy and electron microscopy were applied along with cathodoluminescence for cement quantification. The underlying Snadd Formation is included in the analysis to serve as a comparison to the two other formations.

The results of the analysis show a good reservoir potential in the middle Reke sequence of the Fruholmen Formation, with fair potential in the Nordmela Formation as a whole. The upper and lower Krabbe and Akkar sequences of the Fruholmen Formation have poor reservoir potential, and the Snadd Formation has very poor reservoir potential due to silt-sized grains and extremely low porosity. Evidence of compaction, cementation, dissolution, alteration and diagenetic mineral replacement was found in the study. In addition, temperature evidence from mineral data imply an uplift of close to 2km.