Another way of looking at damage or stimulation

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Another way of looking at damage or stimulation

• Equivalent wellbore radius

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Equivalence of Skin and Equivalent wellbore radius
Equivalence
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Example

• Assume rw 0.3 ft .

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Solutions to the general diffusivity equation
continued

• (radial continued)

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The general diffusivity equation

• Inner boundary(well)
• No flow (shut-in)
• Constant rate
• Constant flowing pressure

• Outer boundary
• Infinite acting
• No flow
• Constant pressure (or given influx)

Wellbore storage or not

• Time behavior
• Transient
• Stabilized (time invariant in some respect)
• Steady-state
• Pseudo-steady state
• Boundary dominated flow regime

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Pseudo-Steady-state

• Inner boundary q is given
• Outer boundary no flow
• Time aspect already stabilized

p(r)
pwf
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Pseudo Steady-state flow relation Field units

• With average pressure
• Deliverability
• Ideal Real

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Pseudo-steady state Productivity Index

• Definition
• Dimensionless part
• In ideal case
• Reality
• Flow efficiency
• Damage Ratio DR1-FE

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Example

• Assume re 2100 ft and rw 0.3 ft
• Pseudo-steady state
• If the drawdown, ( p pwf) 1000 psi, how much
  psi is lost "in the skin zone"?
• What is the flow efficiency?
• What is the damage ratio?

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Pseudo Steady-state flow relation Field units
Wellbore pressure in time (ideal)
Real
Average pressure
pwf
t