AAPG Bulletin, V. 84, No. 9 (September 2000), P. 1325-1339.

Modeling Quartz Cementation and Porosity in Middle Jurassic Brent Group Sandstones of the Kvitebjørn Field, Northern North Sea¹

Olav Walderhaug²

©Copyright 2000. The American Association of Petroleum Geologists. All rights reserved.
¹Manuscript received January 15, 1999; revised manuscript received March 9, 2000; final acceptance March 15, 2000.
²Statoil a.s, N-4035, Stavanger, Norway; e-mail: [email protected]
Support from Statoil during the course of this study is gratefully acknowledged. Statoil, Elf Norge, and Norsk Hydro are thanked for permission to present data from wells 34/11-1 and 34/11-3T2. The original manuscript was improved by the comments of Per Arne Bjørkum, Knut Bjørlykke, Edward Prestholm, and referees Sal Bloch, J. F. Brint, and M. S. Poelchan. Mogens Ramm kindly provided the temperature history made for the Brent Group in 34/11-1 with Petromod 2D.

ABSTRACT

Petrographic study of deeply buried Middle Jurassic Brent Group sandstones from the Kvitebjørn gas field in the Norwegian sector of the North Sea shows that quartz cement volumes range from less than 1% to almost 30% over short distances, and porosity ranges from 5 to 30%. A clear correlation between quartz surface area and quartz cement volume indicates that this variation is due to differences in quartz surface area available for quartz overgrowth formation, which, in turn, is a function of grain size, abundance of grain coatings, and quartz clast abundance. The correlation between quartz surface area and quartz cement volume also suggests that the quartz cementation process is a strongly precipitation rate-controlled process, and that quartz cementation can indeed be modeled quantitatively by modeling the precipitation step in the quartz cementation process.