Mechanisms of Quartz Cementation in North Sea Reservoir Sandstones: Constraints From Fluid Compositions
Published:January 01, 1993
Andrew C. Aplin, Edward A. Warren, Shona M. Grant, Andrew G. Robinson, 1993. "Mechanisms of Quartz Cementation in North Sea Reservoir Sandstones: Constraints From Fluid Compositions", Diagenesis and Basin Development, A. D. Horbury, A. G. Robinson
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Quartz occurs widely as a cement in pre-Tertiary North Sea reservoir sands. Fluid inclusion and oxygen isotope data show that much of the cement formed in the Tertiary from 18O-rich waters with variable, but often high salinities. The volume of this type of water is limited and is unlikely to be more than the void space of the sedimentary basin. The mineralizing fluids also show considerable compositional heterogeneity over relatively small areas and depth ranges.
The composition and compositional heterogeneity of the mineralizing fluids limit the mechanisms by which silica transport and quartz cementation could have occurred. Meteoric recharge is ruled out. Mass balance considerations strongly suggest that compaction-driven flow is extremely unlikely to have led to the type of pervasive quartz cementation observed in the pre-Tertiary North Sea section. The compositional heterogeneity of the mineralizing fluids suggests that large-scale convective overturn is also an unlikely transport mechanism. It is probable that the silica required for quartz cementation was supplied locally and not by large-scale fluid flow. We believe that the fluid data restrict potential silica transport mechanisms to: (1) reservoir-scale convection and (2) diffusion. However, significant mass transport by either of these mechanisms has yet to be demonstrated in sedimentary basins.
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Diagenesis and Basin Development
This publication grew out of a conference of the same name held in 1991. Most, though not all, of the chapters included in the volume were presented at that conference. The purpose of the volume is to examine links between sediment diagenesis--and consequent porosity and permeability modification--and aspects of the development of sedimentary basins. The papers in the book provide some important guidelines and insights that may be useful to the exploration geologist in the development of new play concepts, and to the academician many stimulating ideas for further research.