2 p&p&rock texture[1]
TRANSCRIPT
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Porosity and
Permeability
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Porosity
The void spaces between grains
Can be primary or secondary
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Porosity
Porosity (%) =! volume of voids x 100! ! Total volume of rockHowever, not all porosity is effective
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Permeability
Links between pore spacesthat provide conduits forfluid flow
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Permeability
The value of permeability is governed byDarcys law
Q = K (P1-P2) AuL
Q = rate of flow
K = permeability(P1-P2) = pressure drop across sampleA = cross sectional areaL = length of sampleu = viscosity of fluid
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Permeability
The value of permeability(K) depends upon:
Number of conduits
between pores Size of conduits How straight they are
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Porosity Types
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Porosity Types
Interparticle porosity
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Porosity Types
Interparticle porosity
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Porosity Types
Intercrystalline porosity(dolomitic)
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Porosity Types
Intraparticle porosity
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Porosity Types
Moldic porosity
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Porosity Types
Vuggy porosity
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Porosity Types
Vuggy porosity
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Porosity Types
Fenestral porosity
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Porosity Types
Fracture porosityand permeability
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Porosity Types
Fracture porosityand permeability
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Porosity Types
Can have several different types ofporosity and permeability within one rock
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Porosity Types
Can have several different types of porositywithin one rock
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Porosity/Permeability and
Rock Texture
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Porosity/Permeability and RockTexture
In detrital rocks, porosityand permeability are afunction of rock texture,
including:
Grain shape (roundnessand sphericity)
Grain size
Sorting
Fabric (packing and grain
orientation)
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain shape
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain packing
cubic packing gives higher porosity & permeability vsrhombohedral packing
rhombohedral packing enhanced by compaction
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain size
Theoretically, should be no change in porositywith grain size, but practically porosity can
either increase or decrease with grain size
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain size
remains constant with
decreasing grain size
K increases with grain
size due to increasingsize of pore throats
/ b d R k
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Porosity/Permeability and RockTexture
& K and grain sorting
Porosity increases with
improved sorting
K increases with improved
sorting
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain sorting
Porosity increases with
improved sorting
K increases with improved
sorting
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain orientationvaries on three scales:Microscopic--the scale ofpores and pore throats
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain orientationvaries on three scales:Microscopic--the scale ofpores and pore throats
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain orientationvaries on three scales:
Mesoscopic--scale ofsedimentary structuresand beds
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain orientationvaries on three scales:
Mesoscopic--scale ofsedimentary structuresand beds
P it /P bilit d R k
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Porosity/Permeability and RockTexture
& K and grain orientationvaries on three scales:
Mapscale--scale of depositionalenvironment
R l ti hi b t it &
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Relationship between porosity &permeability
The textural controlof porosity andpermeability resultsin a relationshipbetween the two.
However, thatrelationship is notexact
R l ti hi b t it &
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Relationship between porosity &permeability
R l ti hi b t it &
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Relationship between porosity &permeability