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Capillary Pressure andSaturation History
Capillary Pressure in
Reservoir Rock
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DRAINAGE AND IMBIBITION
CAPILLARY PRESSURE CURVES
Drainage
Imbibition
Swi Sm
Sw
Pd
Pc
0 0.5 1.0
Modified from NExT, 1999, after
DRAINAGE
Fluid flow process in which the saturationof the nonwetting phase increases
IMBIBITION
Fluid flow process in which the saturationof the wetting phase increases
Saturation History - Hysteresis
- Capillary pressure depends on both directionof change, and previous saturation history
- Blue arrow indicates probable path from
drainage curve to imbibition curve at Swt=0.4- At Sm, nonwetting phase cannot flow,resulting in residual nonwetting phasesaturation (imbibition)
- At Swi, wetting phase cannot flow, resulting inirreducible wetting phase saturation (drainage)
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Saturation History
The same Pc value can occur at more than
one wetting phase saturation
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Rock Type
Rock Type (Archies Definition - Jorden and Campbell)
Formations that ... have been deposited under similar
conditions and ... undergone similar processes of laterweathering, cementing, or re-solution....
Pore Systems of a Rock Type (Jorden and Campbell)
A given rock type has particular lithologic (especially pore
space) properties and similar and/or related petrophysical andreservoir characteristics
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Thomeers Parameters for
Capillary Pressure Curves Thomeers Data
Mercury Injection - drainage
Very high capillary pressures
(Vb)P The (assymptotically approached) fraction of bulk
volume occupied by mercury at infinite capillary pressure
(similar to previous parameter, irreducible wetting phase
saturation)
Pd Displacement Pressure, capillary pressure required to
force nonwetting phase into largest pores (same aspreviously discussed)
G Parameter describing pore-size distribution (similar to
previous parameter, 1/. Increasing G (or decreasing ),
suggests poor sorting, and/or tortuous flow paths)
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Modfied from Jordan and Campbell, 1984, vol. 1
Figures 2.4 and 2.5
PT = PORE THROATP - PORE
(Vb)p =is the fractional volume occupied by Hg atinfinite pressure, or total interconnected pore volume.
pdis the extrapolated Hg displacement pressure (psi);pressure required to enter largest pore throat.
Gis pore geometricalfactor; range in size and
tortuosity of pore throats.
Large pd= small pore thorats
Large G= tortuous, poorlysorted pore thorats
.
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8/4/2019 Presion Capilary Historia de La Saturacion
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Note variation in pore properties and permeability within a formation
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Modfied from Jordanand Campbell,
1984, vol. 1
Figure 2.8
size: lower finesorting: verywell sorted
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Modfied from Jordan
and Campbell, 1984, vol. 1
Figure 2.9
size: lower finesorting:moderately
sorted
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Modfied from Jordan
and Campbell, 1984, vol. 1
Figure 2.10
size: uppervery finesorting:
moderatelysorted
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Modfied from Jordan
and Campbell, 1984, vol. 1
Figure 2.11
-effect ofsignificantcementing
and clay
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Modfied from Jordanand Campbell, 1984, vol. 1;after Neasham, 1977
Figure 2.12
Effect ofDispersed Clays
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Capillary Pressure in Reservoirs
A B
Reservoir, o
Aquifer, w1
2
3
Pc = po-pw = 0
Pressure
Depth
dpw=wg/D dh
Free
WaterLevel
dpo=og/D dh
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Fluid Distribution in Reservoirs
Gas & Water
Gas density = g
Oil, Gas & Water
Oil & Water
Oil density = o
Water
Water density = w
A
h1
h2B
Free Oil Level
Free Water Level
Capillary pressure differencebetween
oil and water phases in core APc,ow= h1g(w-o)
Capillary pressure differencebetween
gas and oil phases in core BP
c,go= h
2g(
o-
g)
Modified from NExT, 1999, modified after Welge and Bruce, 1947
Fault
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RELATION BETWEEN CAPILLARY
PRESSURE AND FLUID SATURATION
Free Water Level
Pc
PdOil-Water contact
Hd
Heig
htAboveFreeWaterL
evel(Feet)
0 50 100Sw(fraction)
0 50 100
Sw(fraction)
0
Modified from NExT, 1999, after
Pc
0 50 1000
Pd
Sw(fraction)
Lab Data
-Lab Fluids: ,
-Core sample: k,
J-Function
J-Function
- for k,
Reservoir Data
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Saturation in
Reservoir vs. Depth
Results from two
analysis methods (after ABW)
Laboratory capillary
pressure curve
Converted to reservoir
conditions
Analysis of well logs Water saturation has
strong effect on resistivity
curves (future topic)