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Modelling facility for field-average formation pressure 

LaTeX Math Inline
bodyp(t)
 at any time moment 
LaTeX Math Inline
bodyt
 as response to production flowrates history:


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anchorMatBalSw
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\frac{ds_w}{dt} =\frac{1}{A_e \, h_e \, \phi_e(p)} \left[ \int_{p_i}^p \phi_e(p) \, c_t(p) \, dp  = \Delta Q (t) =  Q^{\downarrow}_tq^{\downarrow}_w(t) - q^{\uparrow}_w(t) + q^{\downarrow}_{WAQ}(t) \right] -  \left[ c_r(p) s_w +c_w(p) s_w  \right] \frac{dp}{dt}



LaTeX Math Block
anchorSo
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\frac{ds_w}{dt} =\frac{1}{A_e \, h_e \, \phi_e(p)} \left[ q^{\downarrow}_o(t) - Q^q^{\uparrow}_o(t) \right] -  \left[ c_r(p) s_o +c_o(p) s_o  \right] \frac{dp}{dt}



LaTeX Math Block
anchorSg
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\frac{ds_w}{dt} =\frac{1}{A_e \, h_e \, \phi_e(p)} \left[ q^(t) + Q^{\downarrow}_{GC}g(t) - q^{\uparrow}_g(t) + Q^q^{\downarrow}_{WAQGC}(t) \right] -  \left[ c_r(p) s_w +c_g(p) s_g  \right] \frac{dp}{dt}


s_w + s_o + s_g = 1

where

LaTeX Math Inline
bodyp_i = p(0)

LaTeX Math Inline
body\Delta Q (t)

LaTeX Math Inline
bodyA_e

LaTeX Math Inline
bodyQ^{\uparrow}_t(t)

full-field cumulative offtakes by the time moment

LaTeX Math Inline
bodyt

LaTeX Math Inline
bodyh_e

LaTeX Math Inline
bodyQ^{\downarrow}_t(t)

full-field cumulative intakes by the time moment

LaTeX Math Inline
bodyt

LaTeX Math Inline
body\phi_e(p)

effective porosity as function of formation pressure 

LaTeX Math Inline
bodyp(t)
 

LaTeX Math Inline
bodyQ^{\downarrow}_{GC}(t)

cumulative volumetric inflow from Gas Cap Expansion

LaTeX Math Inline
bodyc_t(p)


total compressibility as function of formation pressure 

LaTeX Math Inline
bodyp(t)

LaTeX Math Inline
bodyQ^{\downarrow}_{WAQ}(t)

cumulative volumetric inflow from Aquifer Expansion


The direct consequence of the above equations:

LaTeX Math Block
anchorMatBal
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 A_e \, h_e \int_{p_i}^p \phi_e(p) \, c_t(p) \, dp  = \Delta Q (t) =  Q^{\downarrow}_t(t) - Q^{\uparrow}_t(t) + Q^{\downarrow}_{GC}(t) + Q^{\downarrow}_{WAQ}(t)


The MatBal equation 

LaTeX Math Block Reference
anchorMatBal
  is often complemented by constant PI  model of Bottom-Hole Pressure (
LaTeX Math Inline
bodyp^{\uparrow}_{wf}(t)
 for producers and 
LaTeX Math Inline
bodyp^{\downarrow}_{wf}(t)
 for injectors):

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