Microstructures of Deformed and Non-Deformed Sandstones from the North Sea: Implications for the Origins of Quartz Cement in Sandstones

  1. Richard H. Worden2 and
  2. Sadoon Morad3
  1. Q. J. Fisher1,
  2. R. J. Knipe1 and
  3. R. H. Worden2

Published Online: 17 MAR 2009

DOI: 10.1002/9781444304237.ch10

Quartz Cementation in Sandstones

Quartz Cementation in Sandstones

How to Cite

Fisher, Q. J., Knipe, R. J. and Worden, R. H. (2009) Microstructures of Deformed and Non-Deformed Sandstones from the North Sea: Implications for the Origins of Quartz Cement in Sandstones, in Quartz Cementation in Sandstones (eds R. H. Worden and S. Morad), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304237.ch10

Editor Information

  1. 2

    School of Geosciences, The Queen's University, Belfast, BT7 1NN, UK

  2. 3

    Sedimentary Geology Research Group, Institute of Earth Sciences, Uppsala University, Norbyvägen 18 B, S–75236, Uppsala, Sweden

Author Information

  1. 1

    Rock Deformation Research Group, Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK

  2. 2

    School of Geosciences, The Queen's University, Belfast, BT7 1NN, UK

Publication History

  1. Published Online: 17 MAR 2009
  2. Published Print: 3 MAR 2000

ISBN Information

Print ISBN: 9780632054824

Online ISBN: 9781444304237

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Keywords:

  • microstructures of deformed and non-deformed sandstones from North Sea;
  • microstructure of North Sea faults;
  • fault sealing processes;
  • cements in faults and fractures;
  • enhanced diffusive mass transfer within faults;
  • distribution and morphology of quartz within undeformed sandstones of North Sea;
  • quartz cement volume versus clay content;
  • origin of cements within faults and fractures;
  • effect of temperature/burial depth on quartz dissolution and precipitation

Summary

Microstructural analysis of approximately 400 faults and fractures, from 28 gas and oil fields within the North Sea, has shown that mesocrystalline quartz cement is not present in significant quantities within any deformation features that acted as conduits for fluid flow. Pyrite, barite, anhydrite, dolomite, calcite and siderite were, however, identified as cements within parts of deformation features that experienced deformation-induced dilation. These cements probably precipitated from fluids focused along the deformation features. This supports isochemical models of quartz cementation, which suggest that it is unlikely that quartz cement in reservoirs originated from fluids flowing along faults.

Cataclastic faults with quartz cement are relatively common within clean sandstones that have been buried to > 90°C. However, these faults experienced pervasive grain fracturing resulting in a rapid decrease in porosity and permeability and are therefore unlikely to have been conduits for fluid flow. Instead, quartz cementation probably occurred because newly fractured, clean grain surfaces generated during cataclastic deformation provided favourable sites for the precipitation of quartz cement. The quartz cement was generated by local processes (occurring within, and up to a distance of ∼1 m from, the fault) such as quartz grain-to-grain dissolution or quartz dissolution along stylolites.

In many reservoir sandstones, the distribution of quartz cement is influenced by the quantity and textural distribution of detrital and authigenic phyllosilicates. The presence of minor clays at quartz grain-to-grain contacts enhances silica solubility and therefore increases its supply for localized quartz cementation. However, grain-coating and pore-filling clays suppress the growth of authigenic quartz by reducing the surface area available for its precipitation. Small variations in the quantity and textural distribution of clays therefore dictate whether a particular part of a sandstone experiences quartz grain-to-grain dissolution and/or quartz cementation. As a consequence of this, the maximum quantity of quartz cement is found within sandstones containing small amounts of detrital clays concentrated at grain-to-grain contacts or stylolites where enhanced quartz grain contact dissolution is possible and precipitation sites are not occluded by too many clays. Fault-rocks experience enhanced grain-contact quartz dissolution relative to their host sediments, when clays are inserted at grain contacts during deformation.