In order to translate it to the Datum one needs to:
1 | Estimate gauge readings at formation top p_{\rm top} using the wellbore fluid density \rho_f gradient |
| ||
2 | Recalculate the pressure at formation top to the Datum using regional hydrostatic pressure gradient GP |
|
- :
\displaystyle
p_{\rm top}(t) = p_{\rm gauge}(t) + g \cdot \int_{z_{\rm gauge}}^{z_{\rm top}} \rho_f(z) dz
- : \displaystyle p_{\rm dat}(t) = p_{\rm top}(t) + GP \cdot (z_{\rm dat} - z _{\rm top})
where
z_{\rm gauge} | TVDss of downhoile gauge |
z_{\rm top} | TVDss of formation top |
p_{\rm gauge}(t) | gauge pressure readings |
p_{\rm top}(t) | estimated wellbore pressure at formation top |
p_{\rm dat}(t) | estimated Datum Pressure |
GP | regional hydrostatic pressure gradient |
\rho_f(z) | wellbore fluid density as function of TVDSS |
g | Standard gravity constant |
When wellbore fluid density is fairly constant between the gauge location and formation top then one can simplify the Datum Pressure calculation to:
(3) | p_{\rm dat}(t) = p_{\rm gauge}(t) + g \cdot \rho_f \cdot (z_{\rm top} - z_{\rm gauge}) + GP \cdot (z_{\rm dat} - z _{\rm top}) |
See Also
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Pressure Testing & Production Analysis