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Determination of OGIP for Wells in
Pseudosteady-State-Old Techniques, New Approaches
By Mazher Ibrahim and R.A. Wattenbarger Texas
AM University M. Wael Helmy, El Paso Production
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Problem Statement
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Problem Statement
Real gas pseudo-pressure
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Problem Statement
Non- Linearity
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Problem Statement
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Objectives

• Present the shortcoming in using initial
  properties
• Present new Pseudotime
• Present new Pseudotime and superposition
• Calculate accurate OGIP with
• Properties change with pressure
• Rate variations

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Simulation Case 1 Constant Rate
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Simulation Case 1, Constant Rate
Simulation Data
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Production History for Simulation Case 1
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m(pi) - m(pwf )/qg vs. t Plot
Non-Linearity
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OGIP from Tangent Slope
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New Method Normalized Pseudotime
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New Normalized Pseudotime
Normalized Pseudotime take into account the
effect of properties change with pressure
1. Porosity
2. Update initial water saturation
3. Update total compressibility
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Dm(p)/qg vs. t and tn
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Simulation Case 2 Variable Rate
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Production History for Simulation Case 2
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Superposition Time (Super-t)
Superposition take into account the effect of
rate and pwf change
PSS Superposition Equation
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m(pi) - m(pwf )/qg vs. Super-t Plot
Non-Linearity Problem (No unique straight line)
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New Method Normalized Pseudotime and
Superposition
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New Method (Super-tn)
Normalized Pseudotime and Superposition take into
account the effect of- 1. Rate and pwf
change 2. Properties change with pressure
Normalized Pseudotime and Superposition
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m(pi) - m(pwf )/qg vs. Super-t and Super-tn
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m(pi) - m(pwf )/qg vs. Super-tn
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VBA Program
Output of Program
Data Required
Stop
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Field Case 1 Well H-58
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Reservoir Data for Well H-58
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Production Data for Well H-58
Gp 6.29 BscfProduction time 532 day
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m(pi) - m(pwf )/qg vs. Super-t Super-tn
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OGIP from Iteration Procedures
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Reservoir Data for Well H-60
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Production Plot for Well H-60
Gp 5.003 BscfProduction time 659 day
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m(pi) - m(pwf )/qg vs. Super-t Super-tn
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OGIP from Iteration Procedures
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Conclusions
A new normalized pseudotime is proposed in order
to improve the accuracy of calculating the OGIP.
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Conclusions
Superposition with the new normalized pseudotime
gives the accurate OGIP at any change in rate and
properties.
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Conclusions
We should take into account the change in
porosity and initial water saturation with
average pressure in calculating the OGIP
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Thanks