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Shut-in formation pressure estimate based on a wellbore sandface pressure after a given well is shut-in for

p_e = p_{wf}(t_e) \bigg|_{q = 0}

Well intervention

This definition is based on the practical observation of wellbore pressure in shut-in wells for well intervention purposes.

It is the simplest and the most popular definition of formation pressure and is widely used in all upstream industry applications.

The definition of shut-in time

Some conventions are to pick

Boundary-average 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

Pressure Testing

This definition is based on the idea that there is a boundary line

The advantage of this method over

• it provides more accurate estimate of the pressure away from a given well
• is not dependent on

  LaTeX Math Inline
  body t_e

  convention, which may be not valid for a given well

Field-average formation pressure estimate within the drainage area

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

Well Flow Performance Analysis

This definition is based on previous estimates of productivity index and assumption that it stays constant

Historically this definition is marked with a different symbol

9-cell formation pressure estimate from reservoir flow simulation model

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

Dynamic Modelling

It defines fformation pressure as an average of numerically calculated pressure values in 9 grid cells of reservoir flow simulation model

It provides a very rough and often inaccurate estimate of formation pressure for planning new wells, workovers, well performance analysis and testing existing dynamic model against other estimates.

It is widely used in history matching as input parameter to match with.