The location of a downhole gauge may not match the formation top.
In order to translate it pressure from downhole gauge to the Datum one needs to:
| 1 | Estimate gauge readings at formation top | LaTeX Math Inline |
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| body | --uriencoded--p_%7B\rm top%7D |
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| p_{\rm top}(t) = p_{\rm gauge}(t) + g \cdot \int_{z_{\rm gauge}}^{z_{\rm top}} \rho_f(z) dz |
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| 2 | Recalculate the pressure at formation top to the Datum using regional hydrostatic pressure gradient |
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| p_{\rm dat}(t) = p_{\rm top}(t) + GP \cdot (z_{\rm dat} - z _{\rm top}) |
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where
When When wellbore fluid density is is fairly condant constant between the gauyge the gauge location and formation top then ine one can simplify the datum pressure the Datum Pressure calculation to:
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| anchor | 1ptop2 |
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| alignment | left |
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p_{\rm dat}(t) = p_{z_{\rm gauge}}(t) + g \cdot \rho_f \cdot (z_{\rm top} - z_{\rm gauge}}) + GP \cdot (z_{\rm dat} - z _{\rm top}) |
In flowing conditions the equations
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and | LaTeX Math Block Reference |
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are both inaccurate as they do not account for pressure losses due to friction.The equation
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should be replaced with a proper solver for wellbore pressure profile.
See Also
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Petroleum Industry / Upstream / Subsurface E&P Disciplines / Pressure Testing & Production Analysis
