laboratory measurement for permeability
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Laboratory Measurement of
Capillary Pressure
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LABORATORY METHODS FOR
MEASURING CAPILLARY PRESSURE
Porous diaphragm method
Mercury injection method
Centrifuge method
Dynamic method
Determination of Pc(Sw) function
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POROUS DIAPHRAGM METHOD FOR
CAPILLARY PRESSURE
Scale of
Brine
Ultra-finefrittedglass disk
Seal ofred oil
squaredpaper
Saran tube
Crude oil
Nitrogenpressure
Neoprenestopper
Nickel-platedspring
Kleenexpaper
Core
Porous diaphragm method ofmeasuring capillary pressure
Modified from Welge and Bruce, 1947
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CAPILLARY PRESSURE USING
POROUS DIAPHRAGM METHOD
Capillarypressure,psia
Wetting phase saturation, %
Measureddata points
Irreducible
Wetting PhaseSaturation
Displacementpressure
0 100
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COMMENTS ON POROUS
DIAPHRAGM METHOD Advantages Very accurate
Can use reservoir fluids
Disadvantages Very slow (days, weeks, months)
Range of capillary pressure is limited bydisplacement pressure of porous disk
Wetting phase of disk should be same as coresample
Holes in porous disk act as capillaries,
allowing only wetting to flow out until
displacement pressure is exceeded
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MERCURY INJECTION METHOD FOR
CAPILLARY PRESSURE
Lucite window
Lucite window
To
0-2,000 psi pressuregauge
Regulating valve
atmosphere
U-tube monometer
Cylinder
0-200 psi pressure gauge
From Purcell, 1949
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COMMENTS ON MERCURY
INJECTION METHOD
Advantages
Results obtained quickly (minutes,hours)
Method is reasonably accurate
Very high range of capillary pressures
Disadvantages
Ruins core / mercury disposal
Hazardous testing material (mercury)
Conversion required between mercury/air
capillary data to reservoir fluid systems
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CENTRIFUGE METHOD FOR
DETERMINING CAPILLARY PRESSURE
Seal Cap Core holder body Window
Tube bodySuppor t d iskO - Ring
From Slobod and others,
1951
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COMMENTS ON
CENTRIFUGE METHOD Advantages
Results can be obtained fairly quickly
(hours, days, weeks) Reasonably accurate
Can use reservoir fluids
Disadvantages Complex analysis required can lead to
calculation errors
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DYNAMIC METHOD OF MEASURING
CAPILLARY PRESSURE
Toatmosphere
Oil burette
Porcelainplate
Oil inlet
PoPg Pc
GasinletGasoutlet
Core
From Brown, 1951
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COMMENTS ON
DYNAMIC METHOD
Advantages
Simulates reservoir flowconditions
Can use reservoir fluids
Disadvantages
Very tedious to perform (weeks,months)
High cost
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AVERAGING CAPILLARY PRESSURE
DATA USING THE LEVERETT
J-FUNCTION
The Leverett J-function was originally an attempt
to convert all capillary pressure data to a
universal curve
A universal capillary pressure curve does not
exist because the rock properties affecting
capillary pressures in reservoir have extreme
variation with lithology (rock type)
BUT, Leveretts J-function has proven valuable
for correlating capillary pressure data within a
lithology (see ABW Fig 3-23).
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EXAMPLE J-FUNCTION FOR
WEST TEXAS CARBONATE
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Water saturation, fraction
J-
function
Jc
Jmatch
Jn1
Jn2
Jn3
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DEFINITION OF LEVERETT J-FUNCTION
( )f
q
s
kC PcSJ wcos
=J-Function is DIMENSIONLESS, for a particular rock type:
Same value of J at same wetting phase saturation for
any unit system, any two fluids, any exact value of k,f(k/f)1/2is proportional to size of typical pore throat
radius (remember k can have units of length2)
C is unit conversion factor (to make J(Sw) dimensionless)
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FlowUnits
Gamma RayLog
PetrophysicalData
PoreTypes
LithofaciesCore
1
2
3
4
5
CorePlugs
CapillaryPressure
f vs k
Pc(Sw) Depends on k,f
High Quality
Low Quality
Function moves up
and right, and
becomes less L
shaped as reservoir
quality decreases
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LEVERETT J-FUNCTION FOR
CONVERSION OF PcDATA
Reservoir
c
Lab
c
w
k
cos
PCk
cos
PC
)J(S
=
=
ff
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J-function is useful for averaging capillarypressure data from a given rock type from a givenreservoir
J-function can sometimes be extended todifferent reservoirs having same lithologies
Use extreme caution in assuming this can bedone
J-function usually not accurate correlation fordifferent lithologies
If J-functions are not successful in reducing thescatter in a given set of data, then this suggeststhat we are dealing variation in rock type
USE OF LEVERETT J-FUNCTION
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