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\delta \left[ \phi \cdot \left( \xi_{O,o} \, s_o + \xi_{O,g} \, s_g \right) \right] = V^{-1} \, \delta q_O
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\delta \left[ \phi \cdot \left( \xi_{G,o} \, s_o + \xi_{G,g} \, s_g \right) \right] = V^{-1} \, \delta q_G
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\delta \left[ \phi \cdot \xi_{W,w} \, s_w \right] = V^{-1} \, \delta q_W

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\phi \cdot \left[ \frac{1}{B_o} \, s_o + \frac{R_v}{B_g} \, s_g  \right] = V^{-1} \, \delta q_O + \phi_i \cdot \left[ \frac{1}{B_{oi}} \, s_o + \frac{R_{vi}}{B_{gi}} \, s_{gi}  \right]
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\phi \cdot \left[ \frac{R_s}{B_o} \, s_o + \frac{1}{B_g} \, s_g  \right] = V^{-1} \, \delta q_G + \phi_i \cdot \left[ \frac{R_{si}}{B_{oi}} \, s_o + \frac{1}{B_{gi}} \, s_{gi}  \right]
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\phi \cdot \frac{1}{B_w} \, s_w  = V^{-1} \, \delta q_W + \phi_i \cdot  \frac{1}{B_{wi}} \, s_{wi} 

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\phi_n \cdot \left[ \frac{1}{B_o} \, s_o + \frac{R_v}{B_g} \, s_g  \right] = V_e^{-1} \, \delta q_O + \left[ \frac{1}{B_{oi}} \, s_o + \frac{R_{vi}}{B_{gi}} \, s_{gi}  \right]
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\phi_n \cdot \left[ \frac{R_s}{B_o} \, s_o + \frac{1}{B_g} \, s_g  \right] = V_e^{-1} \, \delta q_G + \left[ \frac{R_{si}}{B_{oi}} \, s_o + \frac{1}{B_{gi}} \, s_{gi}  \right]
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\phi_n \cdot \frac{1}{B_w} \, s_w  = V_e^{-1} \, \delta q_W + \frac{1}{B_{wi}} \, s_{wi} 

DefinitionsWith new definitions:

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\frac{1}{B_o} \, s_o + \frac{R_v}{B_g} \, s_g  = G_O/\phi_n 
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G_O = V_e^{-1} \, \delta q_O + \left[ \frac{1}{B_{oi}} \, s_o + \frac{R_{vi}}{B_{gi}} \, s_{gi}  \right]
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\frac{R_s}{B_o} \, s_o + \frac{1}{B_g} \, s_g  = G_G/\phi_n
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G_G = V_e^{-1} \, \delta q_G + \left[ \frac{R_{si}}{B_{oi}} \, s_o + \frac{1}{B_{gi}} \, s_{gi}  \right]
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 \frac{1}{B_w} \, s_w  = G_W/\phi_n
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G_W  = V_e^{-1} \, \delta q_W + \frac{1}{B_{wi}} \, s_{wi} 


The equations can be finally explicitly express sturations:

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s_o = \frac{B_o \, (G_o - R_v \, G_G)}{\phi_n \, (1- R_s \, R_v)} 
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s_g = \frac{B_g \, (G_G - R_s \, G_O)}{\phi_n \, (1- R_s \, R_v)} 
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s_w = \frac{B_w \, G_W}{\phi_n} 


Now summing up and taking into account that 

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bodys_o + s_g + s_w = 1
one arrives to a single equation:

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\frac{B_o \, (G_o - R_v \, G_G)}{\phi_n \, (1- R_s \, R_v)} +  \frac{B_g \, (G_G - R_s \, G_O)}{\phi_n \, (1- R_s \, R_v)}  +  \frac{B_w \, G_W}{\phi_n}  =1 
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B_o \, (G_o - R_v \, G_G) + B_g \, (G_G - R_s \, G_O)  + B_w \, G_W \, (1- R_s \, R_v)  = \phi_n \, (1- R_s \, R_v)
Show If
special@self








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body--uriencoded--\phi_n(p) = \phi_e(p)/\phi_%7Bei%7D

normalized porosity

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body\phi(p) =

effective porosity as function of formation pressure 

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bodyp(t)
 

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bodyQ^{\downarrow}_{GC}(t)

cumulative gas influx from Gas Cap Expansion

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body--uriencoded--\phi_%7Bei%7D = \phi_e(p_i)
 

initial effective porosity



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bodyQ^{\downarrow}_{AQ}(t)

cumulative water influx from Aquifer Expansion



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bodyR_{sp}, \; R_{vp}


Initial water saturation

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bodyRFO, \, RFG

Oil and Gas Recovery Factor




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