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Despite of terminological similarity there is a big difference in the way Dynamic Modelling (DM),  Well Flow Performance (WFP) and Well Testing (WT) define formation pressure and productivity index.



Flow rate, q

Productivity Index J


DM

9-cell formation pressure

(1) p_{e9, \ i,j} = \frac{1}{9} \sum_{k=i-1}^{i+1} \sum_{l=j-1}^{j+1} p_{k,l}
(2) p_{e9, \ i,j} = \frac{1}{9} ( p_{i,j} + p_{i, \, j+1} + p_{i, \, j-1} + p_{i-1, \, j} + p_{i-1, \, j} + p_{i-1 \, j-1} + p_{i+1, \, j+1} + p_{i-1 \, j+1} + p_{i+1, \, j-1} )

for each fluid phase individually: p_{e9,o}, \, p_{e9,g}, \, p_{e9,w}

Sandface Flowrates:

Oil sandface flowrate q_o

Gas sandface flowrate q_g

Water sandface flowrate q_w



Sandface Productivity Index:

Oil Sandface Productivity Index J_o = \frac{q_o}{p_{e,o} - p_{wf}}

Gas Sandface Productivity Index J_g = \frac{q_g}{p_{e,g} - p_{wf}}

Water Sandface Productivity Index J_ w = \frac{q_q}{p_{e,w} - p_{wf}}


WFP

Field-average formation pressure estimate 
within the drainage area  A_e

(3) p_r = \frac{1}{A_e} \iint_{A_e} p(x,y,z) dS

Surface flowrates:

Oil surface flowrate q_O

Gas surface flowrate q_G

Water surface flowrate q_W

Liquid surface flowrate q_L


Surface Productivity Index:

Oil Surface Productivity Index J_O = \frac{q_O}{p_r - p_{wf}}

Gas Surface Productivity Index J_G = \frac{q_G}{p_r - p_{wf}}

Water Surface Productivity Index J_W = \frac{q_W}{p_r - p_{wf}}

Liquid Surface Productivity Index J_L = \frac{q_L}{p_r - p_{wf}}

WT

Boundary-average formation pressure estimate 
along the boundary of drainage area  A_e

(4) p_e = \frac{1}{L_e} \int_0^{L_e} p(x,y,z) dl

where L_e is the boundary of drainage area A_e

Total sandface flowrate:

q_t = q_w+q_o+q_g

Total Sandface Productivity Index: J_t = \frac{q_t}{p_e - p_{wf}}

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