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The general form of objective function  for production targets optimisation is given by:


LaTeX Math Block
anchorOF
alignmentleft
G

...

 = \sum_{

...

y=1}^{

...

N_y} \

...

frac{AG_y}{(1+r)^y} \rightarrow \rm max



LaTeX Math Block
anchorAWASG
alignmentleft
AG_y = \sum_{t=1+y_t}^{365+y_t} G_t = \sum_{t=1+y_t}^{365+y_t} 
\left( G_t^{+} - G_t^{-} \right)





LaTeX Math Block
anchorGtPlus
alignmentleft
G_t^{+} =  \sum_{k=1}^{N^{\uparrow}_P} 

...

\left[ R_O(t) \cdot q^{\uparrow}_{O, k}(t) + R_G(t) \cdot  q^{\uparrow}_{G, k}(t) \right] 



LaTeX Math Block
anchorGtMinus
alignmentleft
G_t^{-} = 
 \sum_{k=1}^{N^{\uparrow}_P} C^{\uparrow}_{

...

L,k} \cdot q^{\uparrow}_{

...

L, k}(t)

...

+\sum_{

...

k=1}^{N^{\

...

uparrow}_

...

P} C^{\

...

uparrow}_{

...

O,

...

k} \cdot q^{\

...

uparrow}_{

...

O, 

...

k} (t)

...

+\sum_{

...

k=1}^{N^{\

...

uparrow}_

...

P} C^{\

...

uparrow}_{G,

...

k} \cdot q^{\

...

uparrow}_{G, 

...

k} 

...

where

LaTeX Math Inline
bodyq^{\uparrow}_{O, k}

volume/day

oil production rate for 

LaTeX Math Inline
bodyk
-th producer

LaTeX Math Inlinebody
(t)
+\sum_{k=1}^{N^{\uparrow}_P} C^{\uparrow}_{
O
W,k}
cash/volume

cost of produced oil treatment and transportation from 

LaTeX Math Inline
bodyk
-th wellhead to CMS

LaTeX Math Inline
bodyR_O

cash/volumeoil selling price

LaTeX Math Inline
bodyq^{\uparrow}_{G, k}

volume/day

gas production rate for 

LaTeX Math Inline
bodyk
-th producer

LaTeX Math Inline
bodyC^{\uparrow}_{G,k}

cash/volume

cost of produced gas treatment and transportation from 

LaTeX Math Inline
bodyk
-th wellhead to CMS

LaTeX Math Inline
bodyR_G

cash/volumegas selling price

LaTeX Math Inline
bodyq^{\uparrow}_{W, k}

volume/day

water production rate for 

LaTeX Math Inline
bodyk
-th producer

LaTeX Math Inline
bodyC^{\uparrow}_{W,k}

cash/volume

cost of produced water treatment and transportation from 

LaTeX Math Inline
bodyk
-th wellhead to CMS

LaTeX Math Inline
bodyN^{\uparrow}_P

counts

number of producers at 

LaTeX Math Inline
bodyt

LaTeX Math Inline
bodyq^{\uparrow}_{L, k}

volume/day

liquid production rate for 

LaTeX Math Inline
bodyk
-th producer

LaTeX Math Inline
bodyC^{\uparrow}_{L, k}

cash/volume

cost of fluid lift from reservoir to the 

LaTeX Math Inline
bodyk
-th wellhead, cash/volume

LaTeX Math Inline
bodyN^{\downarrow}_W

counts

number of water injectors at 

LaTeX Math Inline
bodyt

LaTeX Math Inline
bodyq^{\downarrow}_{W, i}

volume/day

water injection rate for 

LaTeX Math Inline
bodyi
-th water injector

LaTeX Math Inline
bodyC^{\downarrow}_{W,i}

cash/volume

cost of water injection, including purchase, treatment, transportation and pumping into 

LaTeX Math Inline
bodyi
-th well

LaTeX Math Inline
bodyN^{\downarrow}_G

counts

number of gas injectors at 

LaTeX Math Inline
bodyt

LaTeX Math Inline
bodyq^{\downarrow}_{G, i}

volume/day

gas injection rate for 

LaTeX Math Inline
bodyi
-th gas injector

LaTeX Math Inline
bodyC^{\downarrow}_{G,j}

cash/volume

cost of gas injection, including purchase, treatment, transportation and pumping into 

LaTeX Math Inline
bodyi
-th well

LaTeX Math Inline
bodyt

monthstime

The objective function  

LaTeX Math Block Reference
anchorOF
can be rewritten in terms of Surface flowrates 
LaTeX Math Inline
body\{ q^{\uparrow}_L, q^{\downarrow}_W, q^{\downarrow}_G \}
:

LaTeX Math Block
anchorOF_L
alignmentleft
G(t) = \sum_{p=1}^{N^{\uparrow}_P} C^{\uparrow}_{OGW}  \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}
LaTeX Math Block
anchorKPBIE
alignmentleft
C^{\uparrow}_{OGW}(t) = \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} 

where

...

LaTeX Math Inline
bodyY_{w,k} = q_{W,k} / q_{L,k}

...

Watercut in 

LaTeX Math Inline
bodyk
-th well

...

LaTeX Math Inline
bodyY_{g,k} = q_{G,k} / q_{O,k}

...

Gas-Oil Ratio in 

LaTeX Math Inline
bodyk
-th well

 \cdot q^{\uparrow}_{W, k}(t)
+\sum_{i=1}^{N^{\downarrow}_W} C^{\downarrow}_{W,j} \cdot q^{\downarrow}_{W, i}(t)
+\sum_{j=1}^{N^{\downarrow}_G} C^{\downarrow}_{G,j} \cdot q^{\downarrow}_{G, j}(t)
+ C_{WS} \cdot q_{WS}(t)
+ C_{GS} \cdot q_{GS}(t)




LaTeX Math Block
anchor8ZMLG
alignmentleft
q_{WS}(t) = \sum_{i=1}^{N^{\downarrow}_W}  q^{\downarrow}_{W, i}(t) - \sum_{k=1}^{N^{\uparrow}_P} q^{\uparrow}_{W, k}(t) 



LaTeX Math Block
anchorDDXYO
alignmentleft
C_{WS}(t)= \begin{cases} 
C^{\uparrow}_{WS}(t), & \mbox{if } q_{WS}(t)>0 
\\ 
C^{\downarrow}_{WS}(t), & \mbox{if } q_{WS}(t)<0 
\end{cases}



LaTeX Math Block
anchor3YBLD
alignmentleft
q_{GS}(t) = \sum_{j=1}^{N^{\downarrow}_G}  q^{\downarrow}_{G, j}(t) - \sum_{k=1}^{N^{\uparrow}_P} q^{\uparrow}_{G, k}(t)



LaTeX Math Block
anchor0I6LB
alignmentleft
C_{GS}(t)= \begin{cases} 
C^{\uparrow}_{GS}(t), & \mbox{if } q_{GS}(t) > 0 
\\ 
C^{\downarrow}_{GS}(t), & \mbox{if } q_{GS}(t) > 0 
\end{cases}




where

LaTeX Math Inline
bodyN_y

yearsassessment period

LaTeX Math Inline
bodyt

days

running time in the form of the number of days past the start of production 

LaTeX Math Inline
bodyt=0

LaTeX Math Inline
bodyy_t

years

number of whole years past the start of production by the current moment 

LaTeX Math Inline
bodyt

LaTeX Math Inline
bodyr

discount rate





LaTeX Math Inline
body--uriencoded--q%5e%7B\uparrow%7D_%7BO, k%7D(t)

volume/day

oil production rate for 

LaTeX Math Inline
bodyk
-th producer

LaTeX Math Inline
body--uriencoded--C%5e%7B\uparrow%7D_%7BO,k%7D(t)

cash/volume

cost of produced oil treatment and transportation from 

LaTeX Math Inline
bodyk
-th wellhead to CTM

LaTeX Math Inline
bodyR_O(t)

cash/volumeoil selling price

LaTeX Math Inline
body--uriencoded--q%5e%7B\uparrow%7D_%7BG, k%7D(t)

volume/day

gas production rate for 

LaTeX Math Inline
bodyk
-th producer

LaTeX Math Inline
body--uriencoded--C%5e%7B\uparrow%7D_%7BG,k%7D(t)

cash/volume

cost of produced gas treatment and transportation from 

LaTeX Math Inline
bodyk
-th wellhead to CTM

LaTeX Math Inline
bodyR_G(t)

cash/volumegas selling price

LaTeX Math Inline
body--uriencoded--q%5e%7B\uparrow%7D_%7BW, k%7D(t)

volume/day

water production rate for 

LaTeX Math Inline
bodyk
-th producer

LaTeX Math Inline
body--uriencoded--C%5e%7B\uparrow%7D_%7BW,k%7D(t)

cash/volume

cost of produced water treatment and transportation from 

LaTeX Math Inline
bodyk
-th wellhead to CTM

LaTeX Math Inline
body--uriencoded--N%5e%7B\uparrow%7D_P(t)

counts

number of producers at 

LaTeX Math Inline
bodyt

LaTeX Math Inline
body--uriencoded--q%5e%7B\uparrow%7D_%7BL, k%7D(t)

volume/day

liquid production rate for 

LaTeX Math Inline
bodyk
-th producer

LaTeX Math Inline
body--uriencoded--C%5e%7B\uparrow%7D_%7BL, k%7D(t)

cash/volume

cost of fluid lift from reservoir to the 

LaTeX Math Inline
bodyk
-th wellhead, cash/volume




LaTeX Math Inline
body--uriencoded--q_%7BWS%7D(t)

volume/day

water supply/disposal rate

LaTeX Math Inline
body--uriencoded--C%5e%7B\uparrow%7D_%7BWS%7D(t)

cash/volumecost of water supply

LaTeX Math Inline
body--uriencoded--C%5e%7B\downarrow%7D_%7BWS%7D(t)

cash/volumecost of water disposal

LaTeX Math Inline
body--uriencoded--q_%7BGS%7D(t)

volume/daygas supply/disposal rate

LaTeX Math Inline
body--uriencoded--C%5e%7B\uparrow%7D_%7BGS%7D(t)

cash/volumecost of gas supply

LaTeX Math Inline
body--uriencoded--C%5e%7B\downarrow%7D_%7BGS%7D(t)

cash/volumecost of gas disposal

LaTeX Math Inline
body--uriencoded--q%5e%7B\downarrow%7D_%7BW, i%7D(t)

volume/day

water injection rate for 

LaTeX Math Inline
bodyi
-th water injector

LaTeX Math Inline
body--uriencoded--C%5e%7B\downarrow%7D_%7BW,i%7D(t)

cash/volume

cost of water injection, including treatment, transportation and pumping into 

LaTeX Math Inline
bodyi
-th well

LaTeX Math Inline
body--uriencoded--N%5e%7B\downarrow%7D_W(t)

counts

number of water injectors at 

LaTeX Math Inline
bodyt

LaTeX Math Inline
body--uriencoded--q%5e%7B\downarrow%7D_%7BG, i%7D(t)

volume/day

gas injection rate for 

LaTeX Math Inline
bodyi
-th gas injector

LaTeX Math Inline
body--uriencoded--C%5e%7B\downarrow%7D_%7BG,j%7D(t)

cash/volume

cost of gas injection, including purchase, treatment, transportation and pumping into 

LaTeX Math Inline
bodyi
-th well

LaTeX Math Inline
body--uriencoded--N%5e%7B\downarrow%7D_G(t)


counts


number of gas injectors at 

LaTeX Math Inline
bodyt


The objective function  

LaTeX Math Block Reference
anchorOF
can be rewritten in terms of Surface flowrates 
LaTeX Math Inline
body\{ q^{\uparrow}_L, q^{\downarrow}_W, q^{\downarrow}_G \}
 and usual subject to engineering restrictions:


LaTeX Math Block
anchorOF_L
alignmentleft
G_t = \sum_{p=1}^{N^{\uparrow}_P} C^{\uparrow}_{OGW}(t)  \cdot q^{\uparrow}_{L, p}(t)
- \sum_{i=1}^{N^{\downarrow}_W} C^{\downarrow}_{W,i} \cdot q^{\downarrow}_{W, i}(t) 
- \sum_{j=1}^{N^{\downarrow}_G} C^{\downarrow}_{G,j} \cdot q^{\downarrow}_{G, j}(t)
- C_{WS} \cdot q_{WS}(t)
- C_{GS} \cdot q_{GS}(t)



LaTeX Math Block
anchorKPBIE
alignmentleft
C^{\uparrow}_{OGW}(t) = \left[  (R_O(t) -  C^{\uparrow}_{O,p}) + (R_G(t) - C^{\uparrow}_{G,p}) \cdot  Y_{G,p}(t) \right]  \cdot (1- Y_{W,p}(t)) 
- C^{\uparrow}_{L,p} - C^{\uparrow}_{W,p} \cdot Y_{W,p}(t) 



LaTeX Math Block
anchorRateLimit
alignmentleft
0 \leq q^{\uparrow}_{L, p}(t) \leq  q^{\uparrow}_{LMAX, p}(t)



LaTeX Math Block
anchorRateLimit
alignmentleft
0 \leq q^{\downarrow}_{W, i}(t) \leq  q^{\downarrow}_{WMAX, i}(t)



LaTeX Math Block
anchorRateLimit
alignmentleft
0 \leq q^{\downarrow}_{G, j}(t) \leq q^{\downarrow}_{GMAX, j}(t)



LaTeX Math Block
anchorRateLimit
alignmentleft
\sum_{p=1}^{N^{\uparrow}_P} q^{\uparrow}_{L, p}(t) \leq q^{\uparrow}_{LMAX}



LaTeX Math Block
anchorRateLimit
alignmentleft
q^{\downarrow}_{WMIN}(t) \leq 
\sum_{i=1}^{N^{\downarrow}_W} q^{\downarrow}_{W, i}(t) 
\leq q^{\downarrow}_{WMAX}



LaTeX Math Block
anchorRateLimit
alignmentleft
\sum_{j=1}^{N^{\downarrow}_G} q^{\downarrow}_{G, j}(t)
\leq q^{\downarrow}_{GMAX}




LaTeX Math Block
anchorRateLimit
alignmentleft
q^{\downarrow}_{WMIN}(t) = \sum_{p=1}^{N^{\uparrow}_P} q^{\uparrow}_{W, p}(t) 




where

LaTeX Math Inline
body--uriencoded--Y_%7BW,k%7D(t) = q_%7BW,k%7D / q_%7BL,k%7D

Watercut in 

LaTeX Math Inline
bodyk
-th well

LaTeX Math Inline
body--uriencoded--Y_%7BG,k%7D(t) = q_%7BG,k%7D / q_%7BO,k%7D

Gas-Oil Ratio in 

LaTeX Math Inline
bodyk
-th well



Expand
titleSandface Formalism

Usually, each well has a fixed range of its rate variations: 

q^{\uparrow}_{LMIN, p} \leq q^{\uparrow}_{L, p} \leq q^{\uparrow}_{LMAX, p}, \ q^{\downarrow}_{WMIN, i} \leq q^{\downarrow}_{W, i} \leq q^{\downarrow}_{WMAX, i}, \ q^{\downarrow}_{GMIN, j} \leq q^{\downarrow}_{G, j} \leq q^{\downarrow}_{GMAX, j}
LaTeX Math Block
anchorRateLimit
alignmentleft



The objective function  

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

LaTeX Math Block
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}
} G^{\downarrow}_{g,j}  \cdot q^{\downarrow}_{g, j} - 
- C_{WS} \cdot q_{WS}(t)
- C_{GS} \cdot q_{GS}(t)
 \rightarrow \rm max


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


LaTeX Math Block
anchorGw
alignmentleft
G^{\downarrow}_{w,i} = B_{w,i} C^{\downarrow}_{W,i} 


LaTeX Math Block
anchorGg
alignmentleft
G^{\downarrow}_{g,i} = B_{g,i} \cdot C^{\downarrow}_{G,i}


where

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

Water FVF for 

LaTeX Math Inline
bodyk
-th well

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

BHPin 

LaTeX Math Inline
bodyk
-th well

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

Oil FVF for 

LaTeX Math Inline
bodyk
-th well

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

 Solution GOR in 

LaTeX Math Inline
bodyk
-th well

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

Gas FVF for 

LaTeX Math Inline
bodyk
-th well

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

 Vaporized Oil Ratio in 

LaTeX Math Inline
bodyk
-th well




Expand
titleDerivation


Panel
borderColorwheat
bgColormintcream
borderWidth7


LaTeX Math Block
anchor427RB
alignmentleft
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}


LaTeX Math Block
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
G,p} \right]  \cdot q^{\uparrow}_{O, p} 
- C^{\uparrow}_{L,p}  - C^{\uparrow}_{W,p} \cdot Y_{
w
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}


LaTeX Math Block
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
G,p} \right]  \cdot (1- Y_{
w
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 

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

LaTeX Math Block
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
W,p} }
{B_w Y_{
w
W,p} + \left[ (B_o - R_s B_g) + (B_g - R_v B_o) \, Y_{
g
G,p} \right] \cdot (1-Y_{
w
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 

LaTeX Math Block Reference
anchorG_sf
.






Depending on Lift mechanism the rates in equation 

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

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


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


LaTeX Math Block
anchorFQ5IH
alignmentleft
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).



See Also

...

Petroleum Industry / Upstream / Production / Field Development Plan

...

Constant rate production: qL = const ] [ Constant pressure production: pwf pwf = const ]