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Petrophysics/Rheology > 01 - Rock Classification > Flashcards

01 - Rock Classification Flashcards

1
Q

Definition

Rock

A

naturally occurring aggregates of one (monomineralic) or more minerals (polymineralic).

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2
Q

Three major rock groups

A

Igneous rocks -> magmatites

Metamorphic rocks -> metamorphites

Sedimentary rocks -> sediments

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3
Q

Three main processes of rock cycle

A
  1. Erosion & sedimentation
  2. Melting & recrystallization
  3. Sink & recrystallization
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4
Q

Igneous rocks:

three types by occurence and position in crust

A

plutonic

volcanic

subvolcanic

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5
Q

Igneous rocks:

classification according to chemical / mineralogical composition

distingluishes .. (4)

A
  • felsic or silicic rocks (granite, rhyolite) -> acid
  • intermediate rocks (granodiorite, diorite, dacite, andesite)
  • mafic rocks (basalt, gabbro) -> basic
  • ultramafic rocks (peridotite, dunite)
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6
Q

Igneous rocks:
Streckeisen in Exercise 1
Mafic & Ultramafic clasification -> Bilder angucken
TAS

A

Streckeisen in Exercise 1
Mafic & Ultramafic clasification -> Bilder angucken
TAS

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7
Q

Metamorphic rocks:

classification … (4)

A
  • in low, medium, high grade
  • in metamorphic facies zones (mineral paragenesis)
  • after textures (slate, schist, gneiss, fels)
  • after origin (contact-, regional-, subduction-, shock-)
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8
Q

classification in low, medium, high grade:

Sort with increasing metamorphic grade:

  • schist
  • gneiss
  • slate
  • blueschist
  • phyllite
  • migmatite
A

Low grade:

  1. slate
  2. phyllite

Intermediate grade:

  1. blueschist
  2. schist

High grade:

  1. gneiss
  2. migmatite
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9
Q

in metamorphic facies zones:

name the 3 major types of metamorphic series

A
  1. High P/T Series
  2. Medium P/T Series
  3. Low P/T Series
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10
Q

in metamorphic facies zones:

  1. High P/T Series - facies?
A

Zeolite

  • > Blueschist
  • > Eclogite

(high increasing P and low increasing T)

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11
Q

in metamorphic facies zones:

  1. Medium P/T Series - facies?
A

Zeolite

  • > Greenschist
  • > Amphibolite
  • > Granulite

(increasing P and increasing T)

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12
Q

in metamorphic facies zones:

  1. Low P/T Series - facies?
A

Zeolite

  • > Hornfels (Ab-Ep -> Hornblende -> Pyroxene)
  • > Sanidinite or Granulite

( low increasing pressure and high ingreasing T

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13
Q

Sedimentary rocks:

name the 3 major rock classes

A
  1. clastic
  2. chemical
  3. organic
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14
Q

Sedimentary rocks - clastic:

formation processes

A
  • erosion, reworking, transportation
  • deposition & sedimentation
  • compaction and diagenetic processes
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15
Q

Sedimentary rocks - clastic:

what does the physical properties strongly depend on?

(was red marked in lecture)

A
  1. Textural properties:
    - particel dimensions
    - size
    - shape
    - spatial orientation
  2. mineral composition
    - presence and effect of clay minerals
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16
Q

Sedimentary rocks - clastic:

Grain size classification

A

< 0.002 mm Clay

  1. 002 - 0.0063 mm Silt
  2. 0063 - 2.0 mm Sand
  3. 0 - 63 mm Gravel

> 63 mm Boulder

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17
Q

Sedimentary rocks - clastic:

Q,F,L classification

A

Q - quartz
F - feldspar
L - lithoclasts
and matrix

< 5% matrix:

  • > Quartz arenite (Q)
  • > Feldspatic arenite (F,Q)
  • > Lithic arenites (L,Q)

5-50% matrix
Wackes

> 50% matrix:
shales/Mudrocks

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18
Q

Sedimentary rocks - clastic:

Shale

A

mixture of:

clay, silt (some sand) sized particles

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19
Q

Sedimentary rocks - clastic:

Clays - structure

A

alumosilicates with sheet structure and different stacking combinations:

  1. tetrahedral unit with central Si-atom and surrounding O
  2. octahedral unit with central Al and surrounding O atoms and OH groups
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20
Q

Sedimentary rocks - clastic:

Clays - examples

A

Kaolinite (Al)

Illite (K,Al)

Montmorillonite (Ca,Na,Al,Mg,Fe, H2O-layer )

Chlorite (Mg,Al,Fe)

21
Q

Sedimentary rocks - clastic:

Clays - how are exchangeable cations measured ?

A

by cation exchange capacity (CEC)

Smectite/ Montmorillonite HIGH

Kaolinite LOW

22
Q

Sedimentary rocks - chemical:

Carbonates & Evaporate rocks - Formation

A

chemical and biochemical precipitation depending on environments:

  • typically warm
  • shallow
  • clear marine water in low latitudes
23
Q

Sedimentary rocks - chemical:

Carbonates & Evaporate rocks - Sources of secondary porosity

A
  • fracturing
  • solution
  • chemical replacement
24
Q

Sedimentary rocks - chemical:

Carbonates - most abundant carbonate minerals

A
  • calcite CaCO3
  • dolomite CaMg(CO3)2

also:

  • anhydrite
  • chert
  • quartz

+ accessory (phosphates etc.)

25
Q

Sedimentary rocks - chemical:

Carbonates - post-depositional processes

A

dissolution

cementation

recrystallization

dolomitization (increasing porosity)

replacement

26
Q

Sedimentary rocks - chemical:

Carbonates - Classification after Dunham

(Kendall in slides)

A

Picture in Lecture:

Mudstone (mud-supported, < 10% grains)

Wackestone (mud-supported, > 10 % grains)

Packstone (grain-supported, with mud)

Grainstone (grain-supported, without mud)

Boundstone (bound at deposition, intergrown, lamination)

27
Q

Texture includes ..

A

grain size
size distribution
shape
packing

28
Q

What does the grain diameter depend on

A

particles with non-spherical shape depend on technique of determination

1) sieve analysis: minimum cross-sectional axis
2) image or laser scanning: numerical algorithm for representive size distribution

29
Q

Slide 23: Grain size distribution:

well and poorly sorted

A

well: mainly one size occur
poorly: wide range of different sizes

30
Q

Particle size depend on ..

A

environmental setting
tronsporting agent
length and time during transport
depositional conditions

31
Q

Phi-scale

A

phi = -log_2(d)

with d in mm

32
Q

median grain size

A

midpoint at d50 (at 50%)

33
Q

grain sorting S_0

A

how narrow distribution is:

S_0 = (d25/d75)^1/2

34
Q

Skewness S_k

A

symmetry:

S_k = (d25*d75)/d50^2

35
Q

Sieving analysis:

A

sediment pass through series of stacked sieve meshes (by agitation)

wet or dry

Sieve catch grains larger than mesh size

fractions were weighted o get percentages relative to whole sample

36
Q

Atterberg method

A

by sedimentation or settling

measures rate of sedimentation of particles suspended in liquid

not useful for < 5 mikrometer

37
Q

Laser diffraction

A

measures angular dependence of laser light scattered by particles

38
Q

Stereology

mean intercept length of a sphere

A

3D interpretation of 2D cross sections

0.667 as fraction of diameter

was Homework

39
Q

Borehole imaging

A
  1. Optical imaging
  2. Acoustic imaging
  3. Electrical imaging
40
Q

Borehole imaging

  1. Optical imaging
A

Optical & hyperspectral scanning:

  • > downhole scanning
  • > core scanning (360 °)
  • > 3D Channel Spectral data
41
Q

CT-scanning

A

use a x-ray source -> through object and scanned by detector on other side

numelrical agorithm to construct 2D cross section

x-ray attenuation proportional to density

determination of porosity

42
Q

Classification of rock properties:

direc interest for application (4)

A
  • reservoir properties
    (porosity, saturation, permeability)
  • geochemical properties
    (deformation, strength)
  • mineralogical characteristics
    (shale content, fractional min. composition)
  • content of substances of interest
    (ore content)
43
Q

Classification of rock properties:

measured by geophysical methods

A

(elastic/seismic, density, electical, nuclear)

44
Q

Scalar properties

A
  • porosity
  • fluid saturation
  • density
  • nuclear cross-sections
45
Q

Tensorial properties

A
  • permeability
  • deformation modulus
  • strength properties
  • elastic, electrical, thermal, magnetic properties
46
Q

Routine core (plug) analysis

A
  • Porosity (photo)
  • permeability (CT scan)
  • grain density (fluids)
  • gamma
47
Q

Special core analysis

A
  • capillary pressure
  • nuclear magnetic resonance
  • electrical properties
  • acoustic properties
  • clay minerals
  • specific tests
48
Q

isotropic anisotropic

homogenious inhomogenious

A

isotropic-homogeneous: OOO

anisotropic-homogeneous: 000

Isotropic-inhomogenieous: °oO

Anisotropic-inhomogeneous: 0o0

Petrophysics/Rheology (10 decks)

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