Result

Every relation here uses true vertical depth — measured or along-hole depth in a deviated well gives a hydrostatic figure that is too high, which is one of the most consequential mistakes in pressure work. Gradients are treated as constant over each interval, which is reasonable for liquids but a simplification for gas, whose density and therefore gradient change substantially with pressure and temperature; a gas column shut in at surface can show a surprisingly small drop from bottom-hole pressure for exactly this reason. Reference gradients are typical values only, and formation-water salinity, oil composition and temperature all shift them, so measured or lab-derived values should always take priority. Shut-in surface readings must be stabilised, and a reading influenced by trapped pressure, a plugged float or migrating gas will not represent formation pressure. Use these conversions for engineering estimation and cross-checks, not as a substitute for well-specific pressure data or approved well-control procedures.