PETE 310

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PETE 310

• Lectures 12 -13
• Properties of Dry Gases
• (pages 165-187)

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Phase Diagram of a Dry Gas Reservoir
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• DRY GAS RESERVOIRS
• GOR gt 100,000 SCF/STB
• No liquid produced at surface
• Mostly methane

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Standard Conditions

• Unify volumes to common grounds for sales and
  regulatory purposes
• T 60 0F
• P 14.65 15.025 (State dependent)
• Then
• VM RTsc/Psc

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Reservoir Engineering Properties of Dry Gases

• Gas formation volume factor Bg

Reservoir Conditions
Standard Conditions
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Gas Formation Volume Factor

• res bbl/SCF or ft3/SCF

Volume of an arbitrary amount of gas at
reservoir T P
Volume of SAME amount at standard T P
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Gas Formation Volume Factor

• res bbl/SCF or ft3/SCF

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Gas Formation Volume Factor
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Gas Formation Volume Factor

• res bbl/SCF or ft3/SCF

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Viscosity Definition Units

• Viscosity is a measure of the resistance to flow
  exerted by a fluid
• This is called dynamic viscosity and has units of
• centipoise g mass / 100 sec cm
• Kinematic viscosity is viscosity / density, units
  are in
• centistokes centipoise /g/cc

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Reservoir Engineering Properties of Dry Gases

• Gas Viscosity

100oF
150oF
200oF
Viscosity (cp)
200oF
T increasing
150oF
100oF
Pressure
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Viscosity of Ethane
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Viscosity of Gases at Atmospheric Pressure
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Viscosity of Gas Mixtures
See example 6-9
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Example
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Example

• Read Molecular Weights table A-1 page 492
• Read Viscosities figure 6-7
• Apply formula

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Gas Viscosity if Composition
is Unknown
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Viscosity Corrections
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Viscosity of Gases at High Pressure
mratiomat
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Viscosity of Gases at High Pressure
make sure you check the specific gravity range
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Accuracy for Viscosity Correlations?

• At low Ppr and low gravities 2
• Agreement is less accurate as specific gravity
  increases (fig. 6-12 has about 20 accuracy)

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Isothermal Compressibility

• Definition
• Derivative is evaluated at constant T TA and
  specified pressure P PA

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Isothermal Gas Compressibility
TA
TB
P1
PA
P2
V2
V1
Vave (V1V2)/2
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Isothermal Compressibility (Cg)
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Isothermal Compressibility

• Using ideal gas equation

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Isothermal Compressibility

• Using real gas equation

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Gas Compressibility