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Fluid Behaviourand

Rock Properties

Well Test Analysis

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Pressure - Volume BehaviourSingle Component System

Liquid

Gas

Pressure

Volume

Bubblepoint

FIRST BUBBLEOF GAS

LAST DROPOF LIQUID

Dewpoint

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Pressure - Temperature BehaviourSingle Component System

liquid

Criticalpoint

gas

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Three Dimensional Phase DiagramSingle Component System

LiquidGas

Pres

sure

VolumeTemperature

Liquid

GasCriticalpoint

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Pressure - Volume BehaviourTwo Component System

Liquid

Gas

Pressure

Volume

Bubblepoint

FIRST BUBBLEOF GAS LAST DROP

OF LIQUID

Dewpoint

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Pressure - Temperature BehaviourTwo Component System

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Pressure - Temperature BehaviourHydrocarbon Mixture

Temperature

RESERVOIRRESERVOIR RESERVOIR

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5Hydrocarbon Types

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5Oil P-T Behaviour

Temperature

RESERVOIRRESERVOIR RESERVOIR

Black Oil

Volatile Oil

A

A’

C

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5Oil Reservoir below Bubble Point

1. Pressure above Bubble Point. Wellsproduce oil and associated gas.

2. Pressure drops below Bubble Point. Bubbles of solution gas form in reservoir.

3. Critical gas saturation reached.Gas is now mobile.

4. Gas flows towards producing wells.Wells now produce oil, associated gas and solution gas.

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5Oil Reservoir below Bubble Point

1. As fluid is produced, the reservoir pressure drops towards abandonment.2. The Oil production is high at first, rapidly dropping off as more gas is

produced.3. At critical gas saturation, the Gas-Oil ratio rises rapidly to a maximum, then

falls as the lower gas compressibility offsets the increased gas mobility.

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5Hydrocarbon Types

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Temperature

RESERVOIRRESERVOIR RESERVOIR

Gas P-T Behaviour

Wet gas

Dry gas

A

C

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5Hydrocarbon Types

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Temperature

RESERVOIRRESERVOIR RESERVOIR

Gas Condensate P-T Behaviour

Rich gas condensate

Lean gas condensate

AA’

C

B

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5Fluid Parameters

Essential parameters in Well Test Analysis

Volume factor B

Viscosity µ

Compressibility ct

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5Formation Volume factors

BoBwBg

Reservoir conditions

Surface conditions

GasWaterOil

OilGas

Solution gas

Water

Solution gas

Rs Rsw

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5Retrograde Gas Condensate

Bg

Reservoir conditions

Surface conditions

Gas

Gas

Condensate

GLR

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5Formation Volume Factor

B = Fluid volume at standard conditions

Fluid volume at reservoir conditions

This factor transforms surface flow rate valuesinto downhole conditions flow rate values.

Typical values Oil 1.3 to 2.4Gas 0.003 to 0.01

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5Viscosity

Viscosity µ

Is a measure of a fluid’s internal resistance to flow

.. a sort of internal friction.

It depends on pressure, temperature and gravity.

Typical values Oil 0.2 to 30 cpGas 0.01 to 0.05 cp

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5Compressibility

Compressibility ct

Total compressibility

For oil ct = co.So + cw.Sw + cf

For gas ct = cg.Sg + cw.Sw + cf

Typical values Oil 3 x 10-5

Gas 3 x 10-4