Formation pressure (Pe)

Shut-in formation pressure estimate based on a wellbore sandface pressure after a given well is shut-in for $//<![CDATA[ \begin{array}{l}t_e\end{array} //]]>$ hours

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 $//<![CDATA[ \begin{array}{l}t_e\end{array} //]]>$ is specific to each field or sometimes field area depending on the rock properties and the past well intervention experience.

Some conventions are to pick $//<![CDATA[ \begin{array}{l}t_e\end{array} //]]>$ at the end of the radial flow, as the most common number from the past pressure tests, which makes this definition close (but still not equal) to the (2)

Boundary-average formation pressure estimate value along the boundary of drainage area $//<![CDATA[ \begin{array}{l}A_e\end{array} //]]>$

where $//<![CDATA[ \begin{array}{l}L_e\end{array} //]]>$ is the boundary of drainage area $//<![CDATA[ \begin{array}{l}A_e\end{array} //]]>$

Pressure Testing

This definition is based on the idea that there is a boundary line $//<![CDATA[ \begin{array}{l}L_e\end{array} //]]>$ which restricts radial flow around a well, which is a fair assumption in most practical cases.

The advantage of this method over (1) is that:

• it provides more accurate estimate of the pressure away from a given well
• is not dependent on $//<![CDATA[ \begin{array}{l}t_e\end{array} //]]>$ convention, which may be not valid for a given well

Field-average formation pressure estimate within the drainage area $//<![CDATA[ \begin{array}{l}A_e\end{array} //]]>$

Well Flow Performance Analysis

This definition is based on the productivity index

Historically this definition is marked with a different symbol $//<![CDATA[ \begin{array}{l}p_r\end{array} //]]>$ instead of $//<![CDATA[ \begin{array}{l}p_e\end{array} //]]>$

9-cell formation pressure estimate from reservoir flow simulation model

Dynamic Modelling

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

It provides a rough 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.