pet524 saturation 1 ppt

7/23/2019 PET524 Saturation 1 Ppt

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Saturation

• Volume of phase to pore volume

• Wettability

• Tortuosity

•Mobile vs immobile

1) Swir -irreducible water saturation, below which water cannot flow.

2) Swc -connate water saturation existing on discovery of the reservoir. It may ormay not be irreducible.

3) Swi -may mean irreducible, connate, or interstitial, which means saturation

among the interstices, or pores. Interstitial may or may not signify

irreducible. It may be the value on discovery of the reservoir, or the value

at any time thereafter. Swi may also mean initial or original, which truly

means the water saturation on discovery, but it may or may not be

irreducible.



Saturation

Saturation distribution in a reservoir



Saturation



Factors affecting fluid saturations

• Fluid invasion

• Release of confining

pressure

•

Thermal affects




Influence of mud type on saturations

Oil

67.6%

Wtr

32.4%

Oil

53.4%

Oil

26.7%

Wtr 46.6%

Wtr

38.5%

Gas

34.8%

Original After

flushing

At

surface

Water-based Muds

Oil

50.9%

Wtr

49.1%

Oil

32.9%

Oil

26.7%

Wtr

49.1% Wtr 47.7%

Original After

flushing

At

surface

Oil-based Muds

Filtrate18%

Gas 25.6%



Measurement of Fluid Saturation

1. Retort method

- evaporation of the fluids in the pore space

2. Dean-Stark extraction method- the leaching of fluids in the pore space




Retort method

• sample is sealed inside an aluminum cell

and then heated in stages from 400 F to

1100 F

• Advantages: fast, multiple samples run

Picture of a conventional retort

[CoreLab,1983]




Disadvantages of Retort method

Retort oil correction curve

[CoreLab, 1983]

Retort water calibration curves

[CoreLab,1983]

• Coking effect - heating process

burns oil to the pore surfaces.

• results in oil recovery less than the

initial amount in the sample.

• Empirical correction

• removal of both pore water and water

of crystallization.

• Results in high water recovery

Volume of water

in poresCrystallized

water




Dean-Stark extraction method

• vapor of a solvent rises through the core

and leaches out the oil and water.

• water condenses and is collected in a

graduated cylinder.

• solvent and oil continuously cycle through

the extraction process.

• A typical solvent is toluene, miscible with

the oil but not the water.

• Advantage: accurate

• Disadvantage: long time

o* p

V

wtr W

dryW

wetW

oS




Example of Dean-Stark extraction method to determine

saturations

• Obtain the mass of the saturated sample = 57 gms.

• Determine the bulk volume by nondestructive means = 25 cc

• Determine the oil density = 0.88 gm/cc

•

Place the sample in the extraction apparatus and heat the solvent.Record the volume of water collected and when the reading

becomes constant – stop. Vw = 1.4 ml

• After cooling, remove the core and dry, obtain dry weight = 53 gms.

• Using the saturation method, resaturate the sample with

fresh water ( = 1.00 gm/cc) and weigh. = 58 gms.




Example of Dean-Stark extraction method to determine

saturations

• Calculate the pore volume and porosity,

•

Calculate the water saturation

• Calculate the oil saturation

• Calculate the gas saturation

%2025

5

cc500.1

5358 pV

%285

4.1w

S

%5988.0*5

00.1*4.15357o

S

%1359.028.01g

S

pet524 saturation 1 ppt

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