Laboratory Measurement for Permeability

7/22/2019 Laboratory Measurement for Permeability

1/17

Laboratory Measurement of

Capillary Pressure


2/17

LABORATORY METHODS FOR

MEASURING CAPILLARY PRESSURE

Porous diaphragm method

Mercury injection method

Centrifuge method

Dynamic method

Determination of Pc(Sw) function


3/17

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


4/17

CAPILLARY PRESSURE USING

POROUS DIAPHRAGM METHOD

Capillarypressure,psia

Wetting phase saturation, %

Measureddata points

Irreducible

Wetting PhaseSaturation

Displacementpressure

0 100


5/17

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


6/17

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


7/17

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


8/17

CENTRIFUGE METHOD FOR

DETERMINING CAPILLARY PRESSURE

Seal Cap Core holder body Window

Tube bodySuppor t d iskO - Ring

From Slobod and others,

1951


9/17

COMMENTS ON

CENTRIFUGE METHOD Advantages

Results can be obtained fairly quickly

(hours, days, weeks) Reasonably accurate


Disadvantages Complex analysis required can lead to

calculation errors


10/17

DYNAMIC METHOD OF MEASURING

CAPILLARY PRESSURE

Toatmosphere

Oil burette

Porcelainplate

Oil inlet

PoPg Pc

GasinletGasoutlet

Core

From Brown, 1951


11/17

COMMENTS ON

DYNAMIC METHOD

Advantages

Simulates reservoir flowconditions


Disadvantages

Very tedious to perform (weeks,months)

High cost


12/17

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).


13/17

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


14/17

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)


15/17

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


16/17

LEVERETT J-FUNCTION FOR

CONVERSION OF PcDATA

Reservoir

c

Lab

c

w

k

cos

PCk

cos

PC

)J(S

=

=

ff


17/17

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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Laboratory Measurement for Permeability