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In the current debate on the ability of oil emplacement to halt quartz cementation in sandstone oil reservoirs, this paper supports a "yes, it can" answer. Although we find some of the empirical data petroleum fluid inclusion abundances, quartz-depth trends) to be inconclusive, we have made progress in this debate by examining theoretical controls for three end-member quartz cementation scenarios. (1) Silica externally sourced via advection. Oil emplacement must halt quartz cementation because of the associated massive reduction in relative permeability to water. (2) Silica supplied internally, water-wet reservoir. Quartz cementation will be inhibited because the rate of diffusion will be reduced by orders of magnitude, making diffusion the rate controlling step. The degree of inhibition will depend on rock fabric and oil saturation; at very high oil saturations quartz cementation could effectively cease. (3) Silica supplied internally, oil-wet reservoir. Quartz cementation will be halted as water cannot access to grain surfaces.

Moyra has a B.A. degree (geology) from Cambridge University and a Ph.D. in carbonate sedimentology from London University. From 1995 to 1999, she was a postdoctoral research assistant at London and, since then, has been a lecturer at Durham University, United Kingdom. Moyra's research focuses on understanding equatorial carbonates, their reservoir development, and factors influencing their evolution. She works regularly with the industry on applied projects.

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(2016) 'Exceptional reservoir quality in HPHT reservoir settings : examples from the Skagerrak Formation of the Heron Cluster, UK, North Sea.', Marine and petroleum geology., 77 . pp. 198-215. Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. cementation and has had little to no effect on porosity preservation. The formation of welldeveloped authigenic chlorite (>70% surface coating) and, to a lesser extent illite clay coats with burial had a positive effect on porosity preservation even though permeability was marginally reduced in the illite-rich sandstones. A schematic porosity and quartz cement evolution model has been developed which allows for pre-drill prediction of reservoir quality in the Heron Cluster and provide valuable insights for other complex high-pressure hightemperature reservoirs.