Rock Physics of Shale - Stanford University

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$Drilling-induced tensile wall-fractures - Stanford University$

Predicting/measuring Brittleness Brittleness increases the chances of naturally occurring fractures, as well as success of hydrofracs. Brittle materials accommodate strain (deformation) by breaking. In constrast, ductile materials accommodate strain by “flowing.” Not only are ductile materials less likely to create permeable fractures, ductile materials will also allow man-made fractures to close or “heal.” Important practical issue is how to determine geomechanical properties from geophysical measurements. 52 Gary Mavko – Stanford Rock Physics Laboratory
Brittleness: Examples Low Clay (tight sandstone) High Clay Fraction Porosity .01 Clay .12 Porosity .05 Clay .31 Porosity .05 Clay .63 In these examples, ductility depends on (1) composition and (2) confining stress. Brittle failure has little or no plastic flow before failure. Jizba, 1991, Ph.D. Dissertation, Stanford University. Jizba, 1991, Ph.D. dissertation, Stanford Univ. 53 Gary Mavko – Stanford Rock Physics Laboratory
Page 1 and 2: Rock Physics of Shale Gary Mavko -
Page 3 and 4: What is Shale? Wentworth Scale of g
Page 5 and 6: Organic-Rich Shale 5 Gary Mavko - S
Page 7 and 8: What the heck is shale porosity/per
Page 9 and 10: Porosity in Organic-rich Shale Foss
Page 11 and 12: Porosity in Organic-rich Shale . Lo
Page 13 and 14: Kerogen Moduli Inferred from Nanoin
Page 15 and 16: Example Compositions Mineral Barnet
Page 17 and 18: What parameters are we interested i
Page 19 and 20: What parameters are we interested i
Page 21 and 22: € Passey’s 1 Method of TOC Esti
Page 23 and 24: The method employs the overlaying o
Page 25 and 26: What’s the Shale-Gas Geoscience Q
Page 27 and 28: Shale Anisotropy 27 Gary Mavko - St
Page 29 and 30: Why Worry about Anisotropy? • It
Page 31 and 32: Sources of Anisotropy 31 Gary Mavko
Page 33 and 34: Fabric Anisotropy Here we show a ph
Page 35 and 36: Fabric Anisotropy Gneiss horizontal
Page 37 and 38: Shale Anisotropy Sources of shale a
Page 39 and 40: Deposition/Compaction Hypotheses
Page 41 and 42: Velocity Anisotropy from Thinly Lay
Page 43 and 44: Velocity Sensitivity to Effective P
Page 45 and 46: Lab data: Anisotropy vs. Effective
Page 47 and 48: Vertical Fractures 47 Gary Mavko -
Page 49 and 50: Fracture Permeability High Pp Natur
Page 51: Fractures/ Brittleness 51 Gary Mavk
Page 55 and 56: Fractures Usually Prefer Certain Li
Page 57 and 58: Predicting/measuring Brittleness
Page 59 and 60: Quantifying Brittleness In terms of
Page 61 and 62: Quartz and Calcite are more brittle
Page 63 and 64: Poisson’s ratio Young’s Modulus
Page 65 and 66: Modeling 65 Gary Mavko - Stanford R
Page 67 and 68: € Modeling Composition Elastic Mo
Page 69 and 70: Examples Quartz Calcite Dolomite Cl
Page 71 and 72: Example computed trends 71 Gary Mav
Page 73 and 74: Gary Mavko - Stanford Rock Physics
Page 75 and 76: Bandyopadhyay, 2009, Ph.D. disserta
Page 77 and 78: Bedding-Plane Microcracks Adding ho
Page 79 and 80: Bedding-Plane Microcracks Velocitie
Page 81 and 82: Vertical Fracture Modeling Interpre
Page 83 and 84: Vertical Fracture Modeling -- NMO T
Page 85 and 86: Issues • Shale lab data are spars

Rock Physics of Shale - Stanford University

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