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titleSandface Formalism



The objective function  

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anchorOF_L
can be further rewritten in terms of Sandface flowrates 
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body\{ q^{\uparrow}_t, q^{\downarrow}_w, q^{\downarrow}_g \}
:

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anchorG_sf
alignmentleft
G = \sum_{k=1}^{N^{\uparrow}_P} G^{\uparrow}_{t,k} \cdot q^{\uparrow}_{t, k}
- \sum_{i=1}^{N^{\downarrow}_W} G^{\downarrow}_{w,i}  \cdot 
q^{\downarrow}_{w, i}
- \sum_{j=1}^{N^{\downarrow}_G} G^{\downarrow}_{g,j}  \cdot q^{\downarrow}_{g, j} - C^{\uparrow}_{WS,k
- C_{WS} \cdot q_{WS}(t)
- C_{GS} \cdot q^{\uparrow}q_{WSGS}(t)
 \rightarrow \rm max


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anchorGtp
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G^{\uparrow}_{t,k} = \frac{\left[  (R_O -  C^{\uparrow}_{O,k}) + (R_G - C^{\uparrow}_{G,k}) \cdot  Y_{g,k} \right]  \cdot (1- Y_{w,k}) 
- C^{\uparrow}_{L,k} - C^{\uparrow}_{W,k} \cdot Y_{w,k} }
{B_{w,k} Y_{w,k} + \left[ (B_{o,k} - R_{s,k} B_{g,k}) + (B_{g,k} - R_{v,k} B_{o,k}) \, Y_{g,k} \right] \cdot (1-Y_{w,k})}


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anchorGw
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G^{\downarrow}_{w,i} = B_{w,i} C^{\downarrow}_{W,i} 


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anchorGg
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G^{\downarrow}_{g,i} = B_{g,i} \cdot C^{\downarrow}_{G,i}


where

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bodyB_{w,k} = B_w(p_{wf,k}(t))

Water FVF for 

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bodyk
-th well

LaTeX Math Inline
bodyp_{wf,k}(t)

BHPin 

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bodyk
-th well

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bodyB_{o,k} = B_o(p_{wf,k}(t))

Oil FVF for 

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bodyk
-th well

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bodyR_{s,k} = R_s(p_{wf,k}(t))

 Solution GOR in 

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bodyk
-th well

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bodyB_{g,k} = B_g(p_{wf,k}(t))

Gas FVF for 

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bodyk
-th well

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bodyR_{v,k} = R_v(p_{wf,k}(t))

 Vaporized Oil Ratio in 

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bodyk
-th well




Expand
titleDerivation


Panel
borderColorwheat
bgColormintcream
borderWidth7


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anchor427RB
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G(t) = \sum_{p=1}^{N^{\uparrow}_P} \left[ 
(R_O -  C^{\uparrow}_{O,p}) \cdot q^{\uparrow}_{O, p} + (R_G - C^{\uparrow}_{G,p}) \cdot  q^{\uparrow}_{G, p} 
- C^{\uparrow}_{L,p}  - C^{\uparrow}_{W,p} \cdot q^{\uparrow}_{W, p}
\right]  
- \sum_{i=1}^{N^{\downarrow}_W} C^{\downarrow}_{W,j} \cdot q^{\downarrow}_{W, i} 
- \sum_{j=1}^{N^{\downarrow}_G} C^{\downarrow}_{G,j} \cdot q^{\downarrow}_{G, j}


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anchor427RB
alignmentleft
G(t) = \sum_{p=1}^{N^{\uparrow}_P} \left[ 
\left[  (R_O -  C^{\uparrow}_{O,p}) + (R_G - C^{\uparrow}_{G,p}) \cdot  Y_{g,p} \right]  \cdot q^{\uparrow}_{O, p} 
- C^{\uparrow}_{L,p}  - C^{\uparrow}_{W,p} \cdot Y_{w,p} \cdot q^{\uparrow}_{L, p}
\right]  
- \sum_{i=1}^{N^{\downarrow}_W} C^{\downarrow}_{W,j} \cdot q^{\downarrow}_{W, i} 
- \sum_{j=1}^{N^{\downarrow}_G} C^{\downarrow}_{G,j} \cdot q^{\downarrow}_{G, j}


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anchor427RB
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G(t) = \sum_{p=1}^{N^{\uparrow}_P} \left[ 
\left[  (R_O -  C^{\uparrow}_{O,p}) + (R_G - C^{\uparrow}_{G,p}) \cdot  Y_{g,p} \right]  \cdot (1- Y_{w,p}) 
- C^{\uparrow}_{L,p} - C^{\uparrow}_{W,p} \cdot Y_{w,p} 
\right]  \cdot q^{\uparrow}_{L, p}
- \sum_{i=1}^{N^{\downarrow}_W} C^{\downarrow}_{W,j} \cdot q^{\downarrow}_{W, i} 
- \sum_{j=1}^{N^{\downarrow}_G} C^{\downarrow}_{G,j} \cdot q^{\downarrow}_{G, j}

Translating 

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bodyq^{\downarrow}_{W, i}
 and 
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bodyq^{\downarrow}_{G, j}
 to Sandface flowrates 
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bodyq^{\downarrow}_{w, i}
 and 
LaTeX Math Inline
bodyq^{\downarrow}_{g, j}
 with formation volume factor and substituting liquid production rate 
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bodyq^{\uparrow}_{L, p}
 from 
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anchorqL
pageLiquid production rate
 one arrives to:

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anchor427RB
alignmentleft
G(t) = \sum_{p=1}^{N^{\uparrow}_P}  \frac{\left[  (R_O -  C^{\uparrow}_{O,p}) + (R_G - C^{\uparrow}_{G,p}) \cdot  Y_{g,p} \right]  \cdot (1- Y_{w,p}) 
- C^{\uparrow}_{L,p} - C^{\uparrow}_{W,p} \cdot Y_{w,p} }
{B_w Y_{w,p} + \left[ (B_o - R_s B_g) + (B_g - R_v B_o) \, Y_{g,p} \right] \cdot (1-Y_{w,p})}
 
 \cdot q^{\uparrow}_{t, p}
- \sum_{i=1}^{N^{\downarrow}_W} C^{\downarrow}_{W,j} \cdot B_w \cdot q^{\downarrow}_{w, i} 
- \sum_{j=1}^{N^{\downarrow}_G} C^{\downarrow}_{G,j} \cdot B_g \cdot q^{\downarrow}_{g, j}

which is equivalent to 

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anchorG_sf
.






Depending on Lift mechanism the rates in equation 

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anchorG_sf
 may be set directly or calculated from THP and formation pressure 
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bodyp_e
(which is a usual case in injection wells):

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anchor3WM13
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q^{\uparrow}_{t, k} = J_{t,k} \cdot ( p_{e,k} - p_{wf,k} )


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anchor9HEU2
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G^q^{\downarrow}_{w,i} = J_{w,i} \cdot ( p_{wf,i} - p_{e,i} )


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anchorFQ5IH
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G^q^{\downarrow}_{g,i} = J_{g,i} \cdot ( p_{wf,i} - p_{e,i} )


Producing wells may spontaneously vary between Constant rate production: qL = const and Constant pressure production: pwf = const (see Constant rate production: qL = const for alternation details).


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