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AZMAN IKHSAN/SKM2313
1
RESERVOIR ROCK PROPERTIES
Porosity
• Theory on porosity
pores in rocks, pore types, porosity
• Determination of porosity
Determination of porosity in laboratory
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
Porosity• Theory on porosity
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
Porosity• Theory on porosity
Reservoir rock has interconnected pores filled with fluid (oil, gas, water) that
can flow through the rock. There are also pores that are not interconnected
(isolated pores).
Porosity is the fraction of void space in a rock to its bulk volume .
The unit for porosity in the Eq 1 is in percent. The unit can also be in fraction.
1
rock of ebulk volum
space pore of volume
100
b
p
b
p
V
V
V
V
Generally;
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
Porosity
Porosity can be classified into;
1. Original porosity
2. Induced porosity
The original porosity is developed during the deposition of the rock material.
intergrannular porosity in sandstone
intercrystalline and oolitic porosity in limestones
Induced porosity is developed by geologic process subsequent to the
deposition of the rock.
fractures
vug or solution cavities commonly found in limestones
Theory on porosity
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RESERVOIR ROCK PROPERTIES
Porosity
Sand grain
Effective porosity/interconnecte (25%)
Cementing material
Isolated porosity (5%)
Total porosity
(30%)
Theory on porosity
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
Porosity
3 types of porosity
1. Effective porosity
2. Isolated porosity
3. Total porosity
Effective porosity only consider interconnected pores.
Isolated porosity refers to the isolated pores.
Total porosity includes both interconnected and isolated pores.
Which type of porosity is important in reservoir engineering?
Theory on porosity
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
Porosity
Porosity is influenced especially by:
1. Arrangement and shape of the grains
2. Mixture of various shapes and sizes of the grains
3. Amount of cementing material
Large sphere
Small sphere
Cubic packing
48%
Rhombohedral
packing
26%
Varied sizes of spheres affect the
type and volume of the pore.Effect of cementing
material
Porosity
36%
Porosity
20%
Theory on porosity
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
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RESERVOIR ROCK PROPERTIES
Porosity• Porosity measurement
ebulk volum
pore of volume
100
b
p
b
p
V
V
V
V
Measurement made in lab:
Vp , volume of pore can be directly or indirectly measured
Vb , bulk volume can be measured directly or indirectly
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
A
L
Porosity
Direct measurement, Vb
Regular shape samples (cylindrical , cube etc): Measure the dimensions
and calculate the bulk volume
Vb , bulk volume can be measured directly or indirectly
• Porosity measurement
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
Porosity
Indirect measurement,, Vb
Regular and irregular shape samples
Vb , bulk volume can be measured directly or indirectly
A
L
• Porosity measurement
Two methods will be discussed:
- volume of displaced mercury
- gravity method
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RESERVOIR ROCK PROPERTIES
Porosity
Indirect measurement,, Vb
volume of displaced mercury
Hg
• Porosity measurement
Vb , bulk volume can be measured directly or indirectly
Additional volume of mercury after the
sample is pushed into the mercury is equal
to bulk volume of the sample.
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
Balance
Porosity
GravityWtd = weight of dry sample
Wthg = weight of mercury
Wtb = balance reading due to the sample
being immersed into the mercury
A
B
BA
Weight of displaced mercury = (Wtb - (Wtk + Wthg))
Volume of
displaced
mercury
=Weight of displaced mercury
Mercury density
Bulk volume
of sample = Volume of displaced
mercury
Balance
Hg
• Porosity measurement
Indirect measurement,, Vb
Vb , bulk volume can be measured directly or indirectly
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
H2O
Porosity
Vp , pore volume can be measured directly or indirectly
Direct measurement, Vp
Saturating sample with liquid
Wtd = weight of dry sample
Wtt = weight of saturated sample
Wtf = weight of liquid in the sample
= Wtt - Wtk
Vp = (Wtt - Wtk)/rf
• Porosity measurement
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
H2O
Porosity
Vp , pore volume can be measured directly or indirectly
Direct measurement, Vp
Saturating sample with liquid
• Porosity measurement
Vb 35 cc
Wtd 20 g
Wtt 25 g
Wf 5 g
rhof 1.25 g/cc
Vp 4 cc
Porosity 0.114
11.4
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RESERVOIR ROCK PROPERTIES
Porosity
Indirect measurement, Vp
Grains volume by using Boyle’s Law
Helium tank
P1 V1 T1
P2 V2 T1
Sample
cylinder
Stainless
steel discs
P1 V1 = P2 V2
V2 = V1 + Vl + Vs -Vc
line
Vp , pore volume can be measured directly or indirectly
• Porosity measurement
P2 = ?
AZMAN IKHSAN/SKM2313
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RESERVOIR ROCK PROPERTIES
Helium tank
P1 V1 T1
Sample
cylinder
Stainless
steel discs
line
Porosity
P3 V3 T1
P1 V1 = P3 V3
V3 = V1 + Vl + Vs -Vc - Vg
sample
Indirect measurement, Vp
Vp , pore volume can be measured directly or indirectly
• Porosity measurement
Grains volume by using Boyle’s Law
P3 = ?
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RESERVOIR ROCK PROPERTIES
Porosity
P1 V1 = P2 V2 V2 = V1 + Vl + Vs - Vc
V1 + Vl + Vs - Vc = V2 = (P1 V1 )/ P2
Vg = V1 + Vl + Vs - Vc - V3
P1 V1 = P3 V3 V3 = V1 + Vl + Vs - Vc - Vg
Vg = (P1 V1 )/ P2 - (P1 V1 )/ P3
Vp = Vb - Vg
= Vp / Vb = (Vb - Vg)/ Vb
Indirect measurement, Vp
Vp , pore volume can be measured directly or indirectly
• Porosity measurement
Grains volume by using Boyle’s Law
Vl = volume of tubing connecting
helium tank to the sample
cylinder
V1 = reference volume of helium tank
Vs = volume of empty sample cylinder
Vc = volume of stanless steel discs
Vg = grains volume of the core
sample
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RESERVOIR ROCK PROPERTIES
Helium tank
P1 V1 T1
P2 = ?
P3 = ?
Vb 35 cc
P1 100 psia
V1 100 cc
P2 68 psia
P3 85 psia
Vg 29.41 cc
Vp 5.59
porosity 0.160
16.0 %
Vg = (P1 V1 )/ P2 - (P1 V1 )/ P3
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RESERVOIR ROCK PROPERTIES
Porosity• Average porosity
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RESERVOIR ROCK PROPERTIES
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RESERVOIR ROCK PROPERTIES
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