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Reference.org
Pressure gradient
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<p>In <a href="/facts/Hydrodynamics/y7uzSCfg">hydrodynamics</a> and <a href="/facts/Hydrostatics/GYu6ljQ0">hydrostatics</a>, the pressure gradient (typically of <a href="/facts/Earth%2527s_atmosphere/FV97Am25">air</a> but more generally of any <a href="/facts/Fluid/tMQ46Tmz">fluid</a>) is a <a href="/facts/Physical_quantity/S8pWBEpK">physical quantity</a> that describes in which direction and at what rate the <a href="/facts/Pressure/eyc37GRG">pressure</a> increases the most rapidly around a particular location. The pressure gradient is a dimensional quantity expressed in units of <a href="/facts/Pascal_(unit)/Am1To2Qm">pascals</a> per <a href="/facts/Metre/hPhzc1CV">metre</a> (Pa/m). Mathematically, it is the <a href="/facts/Gradient/TsR7uukj">gradient</a> of pressure as a function of position. The gradient of pressure in hydrostatics is equal to the <i><a href="/facts/Body_force/KIQG8TyJ">body force</a> <a href="/facts/Force_density/qnza7XhM">density</a></i> (generalised <a href="/facts/Stevin%2527s_Law/GYu6ljQ0">Stevin's Law</a>). </p><p>In <a href="/facts/Petroleum_geology/jMPyPVmN">petroleum geology</a> and the petrochemical sciences pertaining to <a href="/facts/Oil_well/mNNRJmuE">oil wells</a>, and more specifically within <a href="/facts/Hydrostatics/GYu6ljQ0">hydrostatics</a>, pressure gradients refer to the <a href="/facts/Gradient/TsR7uukj">gradient</a> of vertical pressure in a column of fluid within a <a href="/facts/Wellbore/3d6xu8E5">wellbore</a> and are generally expressed in <a href="/facts/Pounds_per_square_inch/RMdeTlB0">pounds per square inch</a> per <a href="/facts/Foot_(unit)/XKamEGjV">foot</a> (psi/ft). This column of fluid is subject to the compound pressure gradient of the overlying fluids. The path and geometry of the column is totally irrelevant; only the vertical depth of the column has any relevance to the vertical pressure of any point within its column and the pressure gradient for any given <a href="/facts/True_vertical_depth/HAsVzn6P">true vertical depth</a>. </p>