1st Edition

Rock Quality, Seismic Velocity, Attenuation and Anisotropy

By Nick R. Barton Copyright 2007
    766 Pages 610 B/W Illustrations
    by CRC Press

    Seismic measurements take many forms, and appear to have a universal role in the Earth Sciences. They are the means for most easily and economically interpreting what lies beneath the visible surface. There are huge economic rewards and losses to be made when interpreting the shallow crust or subsurface more, or less accurately, as the case may be.

    This book describes seismic behaviour at many scales and from numerous fields in geophysics, tectonophysics and rock physics, and from civil, mining and petroleum engineering. Addressing key items for improved understanding of seismic behaviour, it often interprets seismic measurements in rock mechanics terms, with particular attention to the cause of attenuation, its inverse seismic quality, and the anisotropy of fracture compliances and stiffnesses. 

    Reviewed behaviour stretches over ten orders of magnitude, from micro-crack compliance in laboratory tests to cross-continent attenuation. Between these extremes lie seismic investigation of rock joints, boreholes, block tests, dam and bridge foundations, quarry blasting, canal excavations, hydropower and transportation tunnels, machine bored TBM tunnels, sub-sea sediment and mid-ocean ridge measurements, where the emphasis is on velocity-depth-age models. Attenuation of earthquake coda-waves is also treated, including in-well measurements.

    In the later chapters, there is a general emphasis on deeper, higher stress, larger scale applications of seismic, such as shear-wave splitting for interpreting the attenuation, anisotropy and orientation of permeable 'open' fracture sets in petroleum reservoirs, and the 4D seismic effects of water-flood, oil production and compaction. The dispersive or frequency dependence of most seismic measurements and their dependence on fracture dimensions and fracture density is emphasized. The possibility that shear displacement may be required to explain permeability at depth is quantified.

    This book is cross-disciplinary, non-mathematical and phenomenological in nature, containing a wealth of figures and a wide review of the literature from many fields in the Earth Sciences. Including a chapter of conclusions and an extensive subject index, it is a unique reference work for professionals, researchers, university teachers and students working in the fields of geophysics, civil, mining and petroleum engineering. It will be particularly relevant to geophysicists, engineering geologists and geologists who are engaged in the interpretation of seismic measurements in rock and petroleum engineering.

    The multi-disciplinary scope of seismic and rock quality
    Revealing hidden rock conditions
    Some basic principles of P, S and Q
    Q and Q
    Limitations of refraction seismic bring tomographic solutions

    PART I

    1 Shallow seismic refraction, some basic theory, and the importance of rock type
    1.1 The challenge of the near-surface in civil engineering
    1.2 Some basic aspects concerning elastic body waves
    1.2.1 Some sources of reduced elastic moduli
    1.3 Relationships between Vp and Vs and their meaning in field work
    1.4 Some advantages of shear waves
    1.5 Basic estimation of rock-type and rock mass condition, from shallow seismic P-wave velocity
    1.6 Some preliminary conversions from velocity to rock quality
    1.7 Some limitations of the refraction seismic velocity interpretations
    1.8 Assumed limitations may hide the strengths of the method
    1.9 Seismic quality Q and apparent similarities to Q-rock

    2 Environmental effects on velocity
    2.1 Density and Vp
    2.2 Porosity and Vp
    2.3 Uniaxial compressive strength and Vp
    2.4 Weathering and moisture content
    2.5 Combined effects of moisture and pressure
    2.6 Combined effects of moisture and low temperature

    3 Effects of anisotropy on Vp
    3.1 An introduction to velocity anisotropy caused by micro-cracks and jointing
    3.2 Velocity anisotropy caused by fabric
    3.3 Velocity anisotropy caused by rock joints
    3.4 Velocity anisotropy caused by interbedding
    3.5 Velocity anisotropy caused by faults

    4 Cross-hole velocity and cross-hole velocity tomography
    4.1 Cross-hole seismic for extrapolation of properties
    4.2 Cross-hole seismic tomography in tunnelling
    4.3 Cross-hole tomography in mining
    4.4 Using tomography to monitor blasting effects
    4.5 Alternative tomograms
    4.6 Cross-hole or cross-well reflection measurement and time-lapse tomography

    5 Relationships between rock quality, depth and seismic velocity
    5.1 Some preliminary relationships between RQD, F, and Vp
    5.2 Relationship between rock quality Q and Vp for hard jointed, near-surface rock masses
    5.3 Effects of depth or stress on acoustic joint closure, velocities and amplitudes
    5.3.1 Compression wave amplitude sensitivities to jointing
    5.3.2 Stress and velocity coupling at the Gjøvik cavern site
    5.4 Observations of effective stress effects on velocities
    5.5 Integration of velocity, rock mass quality, porosity, stress, strength, deformability

    6 Deformation moduli and seismic velocities
    6.1 Correlating Vp with the ‘static’ moduli from deformation tests
    6.2 Dynamic moduli and their relationship to static moduli
    6.3 Some examples of the three dynamic moduli
    6.4 Use of shear wave amplitude, frequency and petite-sismique
    6.5 Correlation of deformation moduli with RMR and Q

    7 Excavation disturbed zones and their seismic properties
    7.1 Some effects of the free-surface on velocities and attenuation
    7.2 EDZ phenomena around tunnels based on seismic monitoring
    7.3 EDZ investigations in selected nuclear waste isolation studies
    7.3.1 BWIP – EDZ studies
    7.3.2 URL – EDZ studies
    7.3.3 Äspö – EDZ studies
    7.3.4 Stripa – effects of heating in the EDZ of a rock mass
    7.4 Acoustic detection of stress effects around boreholes

    8 Seismic measurements for tunnelling
    8.1 Examples of seismic applications in tunnels
    8.2 Examples of the use of seismic data in TBM excavations
    8.3 Implications of inverse correlation between TBM advance rate and Vp
    8.4 Use of probe drilling and seismic or sonic logging ahead of TBM tunnels
    8.5 In-tunnel seismic measurements for looking ahead of the face
    8.6 The possible consequences of insufficient seismic investigation due to depth limitations

    9 Relationships between Vp, Lugeon value, permeability and grouting in jointed rock
    9.1 Correlation between Vp and Lugeon value
    9.2 Rock mass deformability and the Vp-L-Q correlation
    9.3 Velocity and permeability measurements at in situ block tests
    9.4 Detection of permeable zones using other geophysical methods
    9.5 Monitoring the effects of grouting with seismic velocity
    9.6 Interpreting grouting effects in relation to improved rock mass Q-parameters


    10 Seismic quality Q and attenuation at many scales
    10.1 Some basic aspects concerning attenuation and Qseismic
    10.1.1 A preliminary discussion of the importance of strain levels
    10.1.2 A preliminary look at the attenuating effect of cracks of larger scale
    10.2 Attenuation and seismic Q from laboratory measurement
    10.2.1 A more detailed discussion of friction as an attenuation mechanism
    10.2.2 Effects of partial saturation on seismic Q
    10.3 Effect of confining pressure on seismic Q
    10.3.1 The four components of elastic attenuation
    10.3.2 Effect on Qp and Qs of loading rock samples towards failure
    10.4 The effects of single rock joints on seismic Q
    10.5 Attenuation and seismic Q from near-surface measurements
    10.5.1 Potential links to rock mass quality parameters in jointed rock
    10.5.2 Effects of unconsolidated sediments on seismic Q
    10.5.3 Influence of frequency variations on attenuation in jointed and bedded rock
    10.6 Attenuation in the crust as interpreted from earthquake coda
    10.6.1 Coda Qc from earthquake sources and its relation to rock quality Qc
    10.6.2 Frequency dependence of coda Qc due to depth effects
    10.6.3 Temporal changes of coda Qc prior to earthquakes
    10.6.4 Possible separation of attenuation into scattering and intrinsic mechanisms
    10.6.5 Changed coda Q during seismic events
    10.6.6 Attenuation of damage due to acceleration
    10.6.7 Do microcracks or tectonic structure cause attenuation
    10.6.8 Down-the-well seismometers to minimise site effects
    10.6.9 Rock mass quality parallels
    10.7 Attenuation across continents
    10.7.1 Plate tectonics, sub-duction zones and seismic Q
    10.7.2 Young and old oceanic lithosphere
    10.7.3 Lateral and depth variation of seismic Q and seismic velocity
    10.7.4 Cross-continent Lg coda Q variations and their explanation
    10.7.5 Effect of thick sediments on continental Lg coda
    10.8 Some recent attenuation measurements in petroleum reservoir environments
    10.8.1 Anomalous values of seismic Q in reservoirs due to major structures
    10.8.2 Evidence for fracturing effects in reservoirs on seismic Q
    10.8.3 Different methods of analysis give different seismic Q

    11 Velocity structure of the earth’s crust
    11.1 An introduction to crustal velocity structures
    11.2 The continental velocity structures
    11.3 The continental margin velocity structures
    11.3.1 Explaining a velocity anomaly
    11.4 The mid-Atlantic ridge velocity structures
    11.4.1 A possible effective stress discrepancy in early testing
    11.4.2 Smoother depth velocity models
    11.4.3 Recognition of lower effective stress levels beneath the oceans
    11.4.4 Direct observation of sub-ocean floor velocities
    11.4.5 Sub-ocean floor attenuation measurements
    11.4.6 A question of porosities, aspect ratios and sealing
    11.4.7 A velocity-depth discussion
    11.4.8 Fracture zones
    11.5 The East Pacific Rise velocity structures
    11.5.1 More porosity and fracture aspect ratio theories
    11.5.2 First sub-Pacific ocean core with sonic logs and permeability tests
    11.5.3 Attenuation and seismic Q due to fracturing and alteration
    11.5.4 Seismic attenuation tomography across the East Pacific Rise
    11.5.5 Continuous sub-ocean floor seismic profiles
    11.6 Age effects summary for Atlantic Ridge and Pacific Rise
    11.6.1 Decline of hydrothermal circulation with age and sediment cover
    11.6.2 The analogy of pre-grouting as a form of mineralization

    12 Rock stress, pore pressure, borehole stability and sonic logging
    12.1 Pore pressure, over-pressure, and minimum stress
    12.1.1 Pore pressure and over-pressure and cross-discipline terms
    12.1.2 Minimum stress and mud-weight
    12.2 Stress anisotropy and its intolerance by weak rock
    12.2.1 Reversal of Ko trends nearer the surface
    12.3 Relevance to logging of borehole disturbed zone
    12.4 Borehole in continuum becomes borehole in local discontinuum
    12.5 The EDZ caused by joints, fractures and bedding-planes
    12.6 Loss of porosity due to extreme depth
    12.7 Dipole shear-wave logging of boreholes
    12.7.1 Some further development of logging tools
    12.8 Mud filtrate invasion
    12.9 Challenges from ultra HPHT

    13 Rock physics at laboratory scale
    13.1 Compressional velocity and porosity
    13.2 Density, Vs and Vp
    13.3 Velocity, aspect ratio, pressure, brine and gas
    13.4 Velocity, temperature and influence of fluid
    13.5 Velocity, clay content and permeability
    13.6 Stratigraphy based velocity to permeability estimation
    13.6.1 Correlation to field processes
    13.7 Velocity with patchy saturation effects in mixed units
    13.8 Dynamic Poisson’s ratio, effective stress and pore fluid
    13.9 Dynamic moduli for estimating static deformation moduli
    13.10 Attenuation due to fluid type, frequency, clay, over-pressure, compliant minerals, dual porosity
    13.10.1 Comparison of velocity and attenuation in the presence of gas or brine
    13.10.2 Attenuation when dry or gas or brine saturated
    13.10.3 Effect of frequency on velocity and attenuation, dry or with brine
    13.10.4 Attenuation for distinguishing gas condensate from oil and water
    13.10.5 Attenuation in the presence of clay content
    13.10.6 Attenuation due to compliant minerals and microcracks
    13.10.7 Attenuation with dual porosity samples of limestones
    13.10.8 Attenuation in the presence of over-pressure
    13.11 Attenuation in the presence of anisotropy
    13.11.1 Attenuation for fluid front monitoring
    13.12 Anisotropic velocity and attenuation in shales
    13.12.1 Attenuation anisotropy expressions e , g and d
    13.13 Permeability and velocity anisotropy due to fabric, joints and fractures
    13.13.1 Seismic monitoring of fracture development and permeability
    13.14 Rock mass quality, attenuation and modulus

    14 P-waves for characterising fractured reservoirs
    14.1 Some classic relationships between age, depth and velocity
    14.2 Anisotropy and heterogeneity caused by inter-bedded strata and jointing
    14.2.1 Some basic anisotropy theory
    14.3 Shallow cross-well seismic tomography
    14.3.1 Shallow cross-well seismic in fractured rock
    14.3.2 Cross-well seismic tomography with permeability measurement
    14.3.3 Cross-well seismic in deeper reservoir characterization
    14.4 Detecting finely inter-layered sequences
    14.4.1 Larger scale differentiation of facies
    14.5 Detecting anisotropy caused by fractures with multi-azimuth VSP
    14.5.1 Fracture azimuth and stress azimuth from P-wave surveys
    14.5.2 Sonic log and VSP dispersion effects and erratic seismic Q
    14.6 Dispersion as an alternative method of characterization
    14.7 AVO and AVOA using P-waves for fracture detection
    14.7.1 Model dependence of AVOA fracture orientation
    14.7.2 Conjugate joint or fracture sets also cause anisotropy
    14.7.3 Vp anisotropy caused by faulting
    14.7.4 Poisson’s ratio anisotropy caused by fracturing
    14.8 4C four-component acquisition of seismic including C-waves
    14.9 4D seismic monitoring of reservoirs
    14.9.1 Possible limitations of some rock physics data
    14.9.2 Oil saturation mapping with 4D seismic
    14.10 4D monitoring of compaction and porosity at Ekofisk
    14.10.1 Seismic detection of subsidence in the overburden
    14.10.2 The periodically neglected joint behaviour at Ekofisk
    14.11 Water flood causes joint opening and potential shearing
    14.12 Low frequencies for sub-basalt imaging
    14.13 Recent reservoir anisotropy investigations involving P-waves and attenuation

    15 Shear wave splitting in fractured reservoirs and resulting from earthquakes
    15.1 Introduction
    15.2 Shear wave splitting and its many implications
    15.2.1 Some sources of shear-wave splitting
    15.3 Crack density and EDA
    15.3.1 A discussion of ‘criticality’ due to microcracks
    15.3.2 Temporal changes in polarization in Cornwall HDR
    15.3.3 A critique of Crampin’s microcrack model
    15.3.4 90°-flips in polarization
    15.4 Theory relating joint compliances with shear wave splitting
    15.4.1 An unrealistic rock simulant suggests equality between ZN and ZT
    15.4.2 Subsequent inequality of ZN and ZT
    15.4.3 Off-vertical fracture dip or incidence angle, and normal compliance
    15.4.4 Discussion of scale effects and stiffness
    15.5 Dynamic and static stiffness tests on joints by Pyrak-Nolte
    15.5.1 Discussion of stiffness data gaps and discipline bridging needs
    15.5.2 Fracture stiffness and permeability
    15.6 Normal and shear compliance theories for resolving fluid type
    15.6.1 In situ compliances in a fault zone inferred from seismic Q
    15.7 Shear wave splitting from earthquakes
    15.7.1 Shear-wave splitting in the New Madrid seismic zone
    15.7.2 Shear-wave splitting at Parkfield seismic monitoring array
    15.7.3 Shear-wave splitting recorded at depth in Cajon Pass borehole
    15.7.4 Stress-monitoring site (SMS) anomalies from Iceland
    15.7.5 SW-Iceland, Station BJA shear wave anomalies
    15.7.6 Effects of shearing on stiffness and shear wave amplitude
    15.7.7 Shear-wave splitting at a geothermal field
    15.7.8 Shear wave splitting during after-shocks of the Chi-Chi earthquake in Taiwan
    15.7.9 Shear-wave splitting under the Mid-Atlantic Ridge
    15.8 Recent cases of shear wave splitting in petroleum reservoirs
    15.8.1 Some examples of S-wave and PS-wave acquisition methods
    15.8.2 Classification of fractured reservoirs
    15.8.3 Crack density and shearing of conjugate sets at Ekofisk might enhance splitting
    15.8.4 Links between shear wave anisotropy and permeability
    15.8.5 Polarization-stress alignment from shallow shear-wave splitting
    15.8.6 Shear-wave splitting in argillaceous rocks
    15.8.7 Time-lapse application of shear-wave splitting over reservoirs
    15.8.8 Temporal shear-wave splitting using AE from the Valhall cap-rock
    15.8.9 Shear-wave splitting and fluid identification at the Natih field
    15.9 Dual-porosity poro-elastic modelling of dispersion and fracture size effects
    15.9.1 A brief survey of rock mechanics pseudo-static models of jointed rock
    15.9.2 A very brief review of slip-interface, fracture network and poro-elastic crack models
    15.9.3 Applications of Chapman model to Bluebell Altamont fractured gas reservoir
    15.9.4 The SeisRox model
    15.9.5 Numerical modelling of dynamic joint stiffness effects
    15.9.6 A ‘sugar cube’ model representation
    15.10 A porous and fractured physical model as a numerical model validation

    16 Joint stiffness and compliance and the joint shearing mechanism
    16.1 Some important non-linear joint and fracture behaviour modes
    16.2 Aspects of fluid flow in deforming rock joints
    16.2.1 Coupled stress-flow behaviour under normal closure
    16.2.2 Coupled stress-flow behaviour under shear deformation
    16.3 Some important details concerning rock joint stiffnesses Kn and Ks
    16.3.1 Initial normal stiffness measured at low stress
    16.3.2 Normal stiffness at elevated normal stress levels
    16.4 Ratios of Kn over Ks under static and dynamic conditions
    16.4.1 Frequency dependence of fracture normal stiffness
    16.4.2 Ratios of static Kn to static Ks for different block sizes
    16.4.3 Field measurements of compliance ZN
    16.4.4 Investigation of normal and shear compliances on artificial surfaces in limestones
    16.4.5 The Worthington-Lubbe-Hudson range of compliances
    16.4.6 Pseudo-static stiffness data for clay filled discontinuities and major shear zones
    16.4.7 Shear stress application may apparently affect compliance
    16.5 Effect of dry or saturated conditions on shear and normal stiffnesses
    16.5.1 Joint roughness coefficient (JRC)
    16.5.2 Joint wall compression strength (JCS)
    16.5.3 Basic friction angle f b and residual friction angle f r
    16.5.4 Empirical equations for the shear behaviour of rock joints
    16.6 Mechanical over-closure, thermal-closure, and joint stiffness modification
    16.6.1 Normal stiffness estimation
    16.6.2 Thermal over-closure of joints and some implications
    16.6.3 Mechanical over-closure
    16.7 Consequences of shear stress on polarization and permeability
    16.7.1 Stress distribution caused by shearing joints, and possible consequences for shear wave splitting
    16.7.2 The strength-deformation components of jointed rock masses
    16.7.3 Permeability linked to joint shearing
    16.7.4 Reservoir seismic case records with possible shearing
    16.7.5 The apertures expected of highly stressed ‘open’ joints
    16.7.6 Modelling apertures with the BB model
    16.7.7 Open joints caused by anisotropic stress, low shear strength, dilation
    16.8 Non-linear shear strength and the critical shearing crust
    16.8.1 Non-linear strength envelopes and scale effects
    16.9 Critically stressed open fractures that indicate conductivity
    16.9.1 The JRC contribution at different scales and deformations
    16.9.2 Does pre-peak or post-peak strength resist the assumed crustal shear stress?
    16.10 Rotation of joint attributes and unequal conjugate jointing may explain azimuthal deviation of S-wave polarization
    16.11 Classic stress transformation equations ignore the non-coaxiality of stress and displacement
    16.12 Estimating shallow crustal permeability from a modified rock quality Q-water
    16.12.1 The problem of clay-sealed discontinuities

    17 Conclusions

    Appendix A – The Qrock parameter ratings
    The six parameters defined
    Combination in pairs
    Definitions of characterization and classification as used in rock engineering
    Notes on Q-method of rock mass classification

    Appendix B – A worked example

    Colour Plates


    Nick Barton

    "This important, wide-ranging compendium of rock physics research is intended to bridge the information gap that exists between rock mechanics engineers involved with projects in civil, mining and petroleum engineering and geophysicists working in areas such as petroleum reservoir and earthquake studies. [...] In the study, largely non-mathematical in nature, the author assembles and refers to a large body of literature concerned with experimental and theoretical studies in which both rock mechanics and geophysics at all scales are involved. [...] [A] most important contribution from which both rock mechanics engineers and geophysicists will benefit immensely." Michael King, Imperial College London, UK

    "Let me first start my review by congratulating Barton for making such a cross-disciplinary effort in this book . . . Barton presents an excellent example of what could be accomplished with such collaboration by providing readers a wide perspective of the applications from both geophysics and geomechanics . . . I found the book particularly enjoyable to read since I am a strong advocate of the cross-discipline fertilization of geophysics and geomechanics. I would recommend it as a reference book to both geophysicists and even more to rock mechanics specialists because of the unique multidisciplinary coverage and immense references."

    – Azra N. Tutuncu, in The Leading Edge, April 2009, Vol. 28 No. 4