L4 Understanding PVT

7/27/2019 L4 Understanding PVT

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4/4/2014 SPE Continuing Education 1

Understanding HydrocarbonFluid Properties and Behavior

Source: Djamel Eddine Ouzzane


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OutlineApplication of Fluid Properties

Volumetric Relationships used by ReservoirEngineers

Different Sources to Obtain Fluid Properties

PVT Analysis and Fluid Compositions

Aspects of Sampling


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Application of Fluid Properties

Phase Behavior and Compositional Conceptsare required to determine.

How much oil or gas is presentHow much can be recovered

How fast it can be recoveredReservoir management and

production strategies

FluidProperties


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Properties Required for ReservoirEngineering Calculations

Formation VolumeFactor of Oil BO

Solution Gas-OilRatio RS

Oil and Gas Densities

Coefficient of IsothermalCompressibility C0

Formation VolumeFactor of Gas Bg

Gas Compressibility

Factor Z

Oil - Gas Viscosities

Coefficient of ThermalExpansion 0


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Gas Formation Volume Factor

Oil

Gas

VR

VSC

Bg Volume at Reservoir (P,T)Volume at (Psc ,Tsc)

Well Stream

=


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Oil Formation Volume Factor

1

1.5

2

2.5

3

3.5

4

0 1000 2000 3000 4000 5000 6000

Pressure [psia]

BoforVolatileOil

1

1.05

1.1

1.15

1.2

1.25

1.3

1.35

BoforBalck

Oil

Volatile Oil Black Oil

Bubble Point


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Gas - Oil RatioGOR - RS

Separator

Stock Tank

Gas

Separator Oil Stock Tank Oil

GOR =Volume of Gas at (Psc, Tsc)

Volume of Oil at (Psc, Tsc)

(Standard Conditions)


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Gas - Oil RatioGOR - RS

0

50

100

150

200

250

300

350

0 1000 2000 3000 4000 5000 6000

Pressure [psia]

Rs[m3/m3]

Bubble Point


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How to Obtain FluidProperties

Laboratory Analysis Black Oil Correlations

Compositional Models Equation of State

Measured Data onFluid Sample @

Reservoir Conditions

Calculated Data usingValidated Correlations

On Specific Oil databases

Calculated Data usingConsistent Thermodynamic

Models based on Fluid Compositions


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1. Laboratory PVT Analysis


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2. Black Oil CorrelationsStanding Correlation for Bubble Point

Rs : Dissolved Gas to Oil Ratio

g : Gas GravityAPI : Oil Stock Tank DensityT : Reservoir Temperature in degrees F


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How to Obtain Fluid Properties

Restricted to the type of oil from which they werederived

2. Black Oil Correlations


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How to Obtain Fluid Properties !

3. Compositional Modeling - Equation of

State - EOS

12-10

2

V

i

L

i

f

f1

B21Z

B21Zln

b

b

a

ax2

22B

ABZln1Z

b

bln i

N

1j

ijj

ii

)bV(b)bV(V

)T(a

bV

RTP

32223 BBABZB3B2AZB1Z


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How to Obtain Fluid Properties !

3. Compositional ModelingEquation of State - EOS

Based on Equilibrium Criteria

Y1 Y2 Y3Yn

X1 X2 X3Xn

Z1 Z2 Z3Zn

Temperature

Pressure

Gas

Liquid

EquilibriumRatio

Fluid Mixture

Ki

Yi

Xi=


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Compositions & Phases

Hydrocarbons NonHydrocarbonsPhase:

Solid/liquid

gas

ParaffinsNaphtenesAromatics Oxygen

NitrogenSulfurCO2

Asphaltenes Wax Resins


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Hydrocarbon Families & OtherReservoir Components

NON HYDROCARBONS

N2upto10%

CO2 4%

H2S 6%

H2, He

Na, K, Fe, Cu,Zn,

CaCl2,

MgCl25%

O2

Aromatics

CyclicAliphatics

Laboratory Analysis - C1-C6 and C7+

HYDROCARBONS

Aliphatic

Paraffins Olefins Naphtenics

Alkanes Alkenes Alkynes


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What are Compositions ?

Asphaltene Structure

Wax (Paraffin) Structure


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Phase Envelope

Bubble point

line

Liquid Vapour

Vapour0

Dew pointline

102040

2-phase Region

A

B

D

E

F0

1000

2000

3000

4000

5000

6000

7000

8000

20 40 60 80 100 120 140 160 180 200

Temperature (oC)

Pressure

(psia)

Critical Point

Dew Point RegionBubble Point Region


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Typical Reservoir FluidCompositions

Component Formula Dry Gas Wet Gas Retrogrde gas Volatile Oil Black OilNitrogen N2 0.30 0.20 3.68 1.21 0.36

Carbon Dioxide CO2 1.10 2.10 1.28 2.10 0.29

Methane CH4 90.00 85.00 78.56 60.50 23.97

Ethane C2H6 4.90 4.70 5.62 7.75 6.42

Propane C3H8 1.70 3.20 3.54 4.75 7.64

iso-Butane i-C4H10 0.60 1.20 0.36 2.27 1.79normal-Butane n-C4H10 0.50 1.00 2.19 2.01 5.29

iso-Pentane i-C5H12 0.30 0.90 0.19 1.96 2.98

normal-Pentane n-C5H12 0.20 0.80 1.98 0.88 3.27

Hexanes C6H14 0.20 0.30 0.68 1.90 4.85

Heptanes C7H16 0.20 0.60 0.51 2.51 7.09

Octanes C8H18 0.44 2.45 7.67

Nonanes C9H20 0.20 1.68 5.19

Decanes C10H22 0.12 1.45 4.47

Undecanes C11H24 0.06 1.05 2.96

Dodecanes plus C12 plus 0.59 5.53 15.76

Total 100.00 100.00 100.00 100.00 100.00


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How to Obtain Fluid Samples ?

Need Fluid PropertiesNeed Samples

Surface Sampling

Bottom Hole Sampling

Formation Tester Sampling


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Surface Sampling


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Bottom Hole Sampling

Preserved Samples

Reservoirs Conditions

Selective SamplingZones

Sampling early in thelife of the reservoir withminimum disturbance

Lower overall cost


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Formation Tester Sampling

Assess reservoir fluidquality

ContaminationMonitoring

Insitu Bubble pointdetermination


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Samples Poor Quality

Is Sample Quality a Concern ?

Maximum

AcceptableUncertainty

Typically


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Is Sample Quality a Concern ?

$


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Conclusions

Fluid properties are required in variousdisciplines of petroleum engineeringPetroleum fluids are complex mixtures andtherefore accurate properties must beobtained

Laboratory analysis generally providereliable dataThe compositional approach is preferredand widely usedSamples may be collected using various

methods however obtaining arepresentative sample is crucial.

Documents

L4 Understanding PVT