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Geomechanical and Petrophysical Properties of Mudrocks

tryueuThe geomechanical and petrophysical properties of mudrocks have become a topic du jour recently, mainly due to the gas shale energy boom. Such properties are also critical for conventional petroleum exploration and production in terms of top seal integrity, wellbore stability and pore pressure prediction for example, as well as for geological CO2 storage and nuclear waste disposal. Characterisation of mudrocks as reservoirs and/or seals requires specialised knowledge and testing equipment due to the response of clay-bearing materials to changes in saturation, fluid composition, effective stress and microstructure. Most sealing mudrocks are rich in clay minerals with small pore throat sizes and high ductility, while the so called gas shales tend to be rich in organic matter and low in clay, allowing them to better sustain natural and induced fracture systems.

This GSL special publication stems from an eponymous conference in 2015. There are a number of high quality papers researching laboratory properties of these materials with a couple more focusing on modelling. There is little in the volume however investigating these properties at a larger scale and ‘petrophysics’ as used here is a misnomer for physical properties (e.g. porosity and permeability) rather than traditional petrophysical log evaluation. As this volume came into being from a conference, this is likely a reflection of submitted content, and does not detract from the extensive laboratory-based research presented.

The volume is divided into three sections, the first covering petrophysical properties comprising seven papers, the second part covers microstructure and mineralogy with five papers along with a third section on fractures with three papers. There is a relatively even split between water saturated over/underburden mudrocks and gas shales. Determinations of porosity and permeability in mudrocks feature strongly, with links made to the impact of stress and microstructure, the latter in the main having SEM images of high quality. Lithology and pore structure effects are also covered, with impacts in areas ranging from engineering geology to shale reservoirs. The section on fracturing covers laboratory experiments, field scale seismicity and hydraulic fracture modelling, generally applicable to shale reservoirs.

The papers are well set out, the vast majority of the diagrams are clearly visible and easy to read with the liberal use of colour throughout a bonus. This book would be a good read for specialists working on mudrocks for various applications and also for people wanting to know more about the topic as the reference lists throughout are very comprehensive.

Reviewed by David Dewhurst

GEOMECHANICAL AND PETROPHYSICAL PROPERTIES OF MUDROCKS, by RUTTER E.H., MECKLENBURGH, J, & TAYLOR, K.G. (editors). Geological Society of London Special Publication No 454. 2017. Geological Society of London. ISBN 978-1-78620-316-8. Hbk. 368pp. ISSN 0305-8719. List Price: £120.  Fellows' Price: £60.00. W: www.geolsoc.org.uk/SP454