Responding to the latest developments in rock physics research, this popular reference book has been thoroughly updated while retaining its comprehensive coverage of the fundamental theory, concepts, and laboratory results. It brings together the vast literature from the field to address the relationships between geophysical observations and the underlying physical properties of Earth materials - including water, hydrocarbons, gases, minerals, rocks, ice, magma and methane hydrates. This third edition includes expanded coverage of topics such as effective medium models, viscoelasticity, attenuation, anisotropy, electrical-elastic cross relations, and highlights applications in unconventional reservoirs. Appendices have been enhanced with new materials and properties, while worked examples (supplemented by online datasets and MATLAB® codes) enable readers to implement the workflows and models in practice. This significantly revised edition will continue to be the go-to reference for students and researchers interested in rock physics, near-surface geophysics, seismology, and professionals in the oil and gas industries.

The Rock Physics Handbook

This paper provides a review of the geomechanics and modeling of geomechanics associated with geologic carbon storage (GCS), focusing on storage in deep sedimentary formations, in particular saline aquifers. The paper first introduces the concept of storage in deep sedimentary formations, the geomechanical processes and issues related with such an operation, and the relevant geomechanical modeling tools. This is followed by a more detailed review of geomechanical aspects, including reservoir stress-strain and microseismicity, well integrity, caprock sealing performance, and the potential for fault reactivation and notable (felt) seismic events. Geomechanical observations at current GCS field deployments, mainly at the In Salah CO2 storage project in Algeria, are also integrated into the review. The In Salah project, with its injection into a relatively thin, low-permeability sandstone is an excellent analogue to the saline aquifers that might be used for large scale GCS in parts of Northwest Europe, the U.S. Midwest, and China. Some of the lessons learned at In Salah related to geomechanics are discussed, including how monitoring of geomechanical responses is used for detecting subsurface geomechanical changes and tracking fluid movements, and how such monitoring and geomechanical analyses have led to preventative changes in the injection parameters. Recently, the importance of geomechanics has become more widely recognized among GCS stakeholders, especially with respect to the potential for triggering notable (felt) seismic events and how such events could impact the long-term integrity of a CO2 repository (as well as how it could impact the public perception of GCS). As described in the paper, to date, no notable seismic event has been reported from any of the current CO2 storage projects, although some unfelt microseismic activities have been detected by geophones. However, potential future commercial GCS operations from large power plants will require injection at a much larger scale. For such large-scale injections, a staged, learn-as-you-go approach is recommended, involving a gradual increase of injection rates combined with continuous monitoring of geomechanical changes, as well as siting beneath a multiple layered overburden for multiple flow barrier protection, should an unexpected deep fault reactivation occur.

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The geomechanics of CO2 storage in deep sedimentary formations

CHANGES IN PERMEABILITY CAUSED BY TRANSIENT STRESSES: FIELD OBSERVATIONS, EXPERIMENTS, AND MECHANISMS Michael Manga, 1 Igor Beresnev, 2 Emily E. Brodsky, 3 Jean E. Elkhoury, 4 Derek Elsworth, 5 S. E. Ingebritsen, 6 David C. Mays, 7 and Chi-Yuen Wang 1 Received 7 November 2011; revised 15 February 2012; accepted 10 March 2012; published 12 May 2012. [ 1 ] Oscillations in stress, such as those created by earth- quakes, can increase permeability and fluid mobility in geo- logic media. In natural systems, strain amplitudes as small as 10 A6 can increase discharge in streams and springs, change the water level in wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to prestimulated values over a period of months to years. Mechanisms that can change permeability at such small stresses include unblocking pores, either by breaking up permeability-limiting colloidal deposits or by mobilizing droplets and bubbles trapped in pores by capillary forces. The recovery time over which permeability returns to the prestimulated value is governed by the time to reblock pores, or for geochemical processes to seal pores. Monitor- ing permeability in geothermal systems where there is abun- dant seismicity, and the response of flow to local and regional earthquakes, would help test some of the proposed mechanisms and identify controls on permeability and its evolution. Citation: Manga, M., I. Beresnev, E. E. Brodsky, J. E. Elkhoury, D. Elsworth, S. E. Ingebritsen, D. C. Mays, and C.-Y. Wang (2012), Changes in permeability caused by transient stresses: Field observations, experiments, and mechanisms, Rev. Geophys., 50, RG2004, doi:10.1029/2011RG000382. INTRODUCTION [ 2 ] The permeability of Earth’s crust is of great interest because it largely governs key geologic processes such as advective transport of heat and solutes and the generation of elevated fluid pressures by processes such as physical com- paction, heating, and mineral dehydration. For an isotropic Department of Earth and Planetary Science, University of California, Berkeley, California, USA. Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa, USA. Department of Earth and Planetary Sciences, University of California, Santa Cruz, California, USA. Department of Civil and Environmental Engineering, University of California, Irvine, California, USA. Department of Energy and Mineral Engineering, Center for Geomechanics, Geofluids, and Geohazards, EMS Energy Institute, Pennsylvania State University, University Park, Pennsylvania, USA. U.S. Geological Survey, Menlo Park, California, USA. Department of Civil Engineering, University of Colorado Denver, Denver, Colorado, USA. Corresponding author: M. Manga, Department of Earth and Planetary Science, University of California, 307 McCone Hall, Berkeley, CA 94720, USA. (manga@seismo.berkeley.edu) material, permeability k is defined by Darcy’s law that relates the fluid discharge per unit area q to the gradient of hydraulic head h, q ¼A kgr rh; m where r is the fluid density, m the fluid viscosity and g is gravity. The permeability of common geologic media varies by approximately 16 orders of magnitude, from values as low as 10 A23 m 2 in intact crystalline rock, intact shales, and fault cores, to values as high as 10 A7 m 2 in well-sorted gravels. Nevertheless, despite being highly heterogeneous, perme- ability can be characterized at the crustal scale in a manner that provides useful insight [e.g., Gleeson et al., 2011]. [ 3 ] The responses of hydrologic systems to deformation provide some insight into controls on permeability, in par- ticular its evolution in time. For example, the water level in wells and discharge in rivers have both been observed to change after earthquakes. Because earthquakes produce stresses that can change hydrogeologic properties of the crust, hydrologic responses to earthquakes are expected, especially in the near field (within a fault length of the Copyright 2012 by the American Geophysical Union. Reviews of Geophysics, 50, RG2004 / 2012 1 of 24 Paper number 2011RG000382 8755-1209/12/2011RG000382 RG2004

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Changes in permeability caused by transient stresses: Field observations, experiments, and mechanisms

Oscillations in stress, such as those created by earthquakes, can increase permeability and fluid mobility in geologic media. In natural systems, strain amplitudes as small as 10 -6 can increase discharge in streams and springs, change the water level in wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to pre-stimulated values over a period of months to years. Mechanisms that can change permeability at such small stresses include unblocking pores, either by breaking up permeability-limiting colloidal deposits or by mobilizing droplets and bubbles trapped in pores by capillary forces. The recovery time over which permeability returns to the pre-stimulated value is governed by the time to re-block pores, or for geochemical processes to seal pores. Monitoring permeability in geothermal systems where there is abundant seismicity, and the response of flow to local and regional earthquakes, would help test some of the proposed mechanisms and identify controls on permeability and its evolution.

Changes in permeability caused by transient stresses: field observations, experiments, and

We describe a numerical investigation of seismicity induced by injection into a single isolated fracture. Injection into a single isolated fracture is a simple analog for shear stimulation in enhanced geothermal systems (EGS) during which water is injected into fractured, low permeability rock, triggering slip on preexisting large scale fracture zones. A model was developed and used that couples (1) fluid flow, (2) rate and state friction, and (3) mechanical stress interaction between fracture elements. Based on the results of this model, we propose a mechanism to describe the process by which the stimulated region grows during shear stimulation, which we refer to as the sequential stimulation (SS) mechanism. If the SS mechanism is realistic, it would undermine assumptions that are made for the estimation of the minimum principal stress and unstimulated hydraulic diffusivity. We investigated the effect of injection pressure on induced seismicity. For injection at constant pressure, there was not a signifi...

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Mark D. Zoback

Papers

Reservoir Geomechanics: Frontmatter