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

The most typical definitions (although they do not cover the full variety of definitions referred in petroleum literature) are summarised in the table below:

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

Surface flowrates:

Oil surface flowrate

Gas surface flowrate

Water surface flowrate

Liquid surface flowrate

Drain-area surface Productivity Index:

Oil Surface Productivity Index

Gas Surface Productivity Index

Water Surface Productivity Index

Liquid Surface Productivity Index

WT

Drain-boundary formation pressure estimate
along the boundary of drainage area

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

where is the boundary of drainage area

Total sandface flowrate:

Total Sandface Productivity Index:

DM

9-cell formation pressure

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

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:

Sandface Flowrates:

Oil sandface flowrate

Gas sandface flowrate

Water sandface flowrate

Sandface Productivity Index:

Oil Sandface Productivity Index

Gas Sandface Productivity Index

Water Sandface Productivity Index

Sometimes the wrong estimations of flowrate stem form the wrong inputs ( or ).

See Also