A diagenetic study of intrabasaltic siliciclastics sandstones from the Rosebank field

In-depth analyses of core samples show that authigenic phases formed during progressive burial with temperatures up to ∼120 °C. The suite of diagenetic phases in siliciclastic sandstones between wells and the different Colsay units vary and are interpreted to result from differences in pore water chemistry and/or detrital mineralogy. Laumontite was formed as a late stage authigenic mineral restricted to cored Colsay 1 and 3 units in well 213/26-1z and has not been observed in the neighbouring 213/27-2 core, which may be explained by differences in pore water pH or CO2 partial pressure. The occurrence of laumontite is often associated with poor reservoir quality, but due to the patchy distribution of this mineral in the Rosebank reservoir sands it appears not to have affected reservoir quality.