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LaTeX Math Block
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q = q_1 + q_2




LaTeX Math Block
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p_{wf} = p_e - q/J



LaTeX Math Block
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J = J_1 + J_2



LaTeX Math Block
anchorpe
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p_e = \frac{J_1 \cdot p_1 + J_2 \cdot (p_2- \rho \, g \, hdelta p_2)}{J_1 + J_2}


where

gravity constant
Well

LaTeX Math Inline
bodyq

total subsurface flowrate of the well

LaTeX Math Inline
bodyJ

total well productivity Index

LaTeX Math Inline
bodyp_e

apparent formation pressure of dual-layer formation

LaTeX Math Inline
bodyh

true vertical height between the layers tops

LaTeX Math Inline
body\rho

wellbore fuid density

LaTeX Math Inline
bodyg

Layer #1

LaTeX Math Inline
body--uriencoded--p_%7Bwf%7D = p_%7Bwf, 1%7D

bottom-hole pr4essure pressure at Layer #1 top

LaTeX Math Inline
bodyq_1

total subsurface flowrate of the Layer #1

LaTeX Math Inline
bodyp_1

formation pressure of the Layer #1

LaTeX Math Inline
bodyJ_1

productivity Index of the Layer #1
Layer #2

LaTeX Math Inline
body--uriencoded--p_%7Bwf2%7D = p_%7Bwf%7D + \rho \, g\, hdelta p_2

bottom-hole pr4essure at Layer #2 top

LaTeX Math Inline
body \delta p_2

wellbore pressure loss between the tips of two layers

LaTeX Math Inline
bodyq_2

total subsurface flowrate of the Layer #2

LaTeX Math Inline
bodyp_2

formation pressure of the Layer #2

LaTeX Math Inline
bodyJ_2

productivity Index of the Layer #2


In many practical cases one can safely assume:

LaTeX Math Block
anchordpk
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\delta p_2 = \rho \, g \, h

where

LaTeX Math Inline
body\rho

wellbore fuid density

LaTeX Math Inline
bodyg

gravity constant

LaTeX Math Inline
bodyh = TVDSS_1 - TVDSS_2

true vertical height between 

LaTeX Math Inline
bodyk
-th layer and reference layer 
LaTeX Math Inline
body--uriencoded--k_%7Breff%7D


The above equations are valid for both producers producers 

LaTeX Math Inline
bodyq>0
and injectors
LaTeX Math Inline
bodyq<0
.


Expand
titleDerivation


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LaTeX Math Block
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p_{wf, 1} = p_{wf} = p_1 - q_1/J_1


LaTeX Math Block
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p_{wf,2} = p_{wf} + \delta p_2 = p_2 - q_2/J_2


This leads to

LaTeX Math Block
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q_1 = J_1 \cdot (p_1 - p_{wf})


LaTeX Math Block
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q_2 = J_2 \cdot (p_2 - p_{wf,2}) = J_2 \cdot ((p_2-\delta p_2)- p_{wf})

and

LaTeX Math Block
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q = q_1 + q_2 = q_1 = J_1 \cdot (p_1 - p_{wf})+ J_2 \cdot ((p_2-\delta p_2)- p_{wf})


LaTeX Math Block
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q =  - (J_1+J_2)\cdot  p_{wf} + J_1 \cdot p_1 + J_2 \cdot (p_2-\delta p_2)

or

LaTeX Math Block
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q =  J \cdot (p_e - p_{wf}), \ {\rm where} \ J = J_1 + J_2 \ {\rm and} \ p_e = J^{-1} \cdot (J_1 \cdot p_1 + J_2 \cdot (p_2-\delta p_2))



See Also

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Petroleum Industry / Upstream /  Production / Subsurface Production / Subsurface E&P Disciplines / Field Study & Modelling / Production Analysis / Productivity Diagnostics

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