Changes

Most sedimentary basins have a rule of thumb for average hydrostatic water pressure gradients. For the Gulf Coast basin, it is 0.465 psi/ft. For Rocky Mountain basins, it is 0.45 psi/ft. For fresh water, it is 0.433 psi/ft. If measured hydrostatic pressure is not available for a well, find out the accepted rule-of-thumb average hydrostatic pressure gradient for the depth of the zone of interest where the well is located.

Most sedimentary basins have a rule of thumb for average hydrostatic water pressure gradients. For the Gulf Coast basin, it is 0.465 psi/ft. For Rocky Mountain basins, it is 0.45 psi/ft. For fresh water, it is 0.433 psi/ft. If measured hydrostatic pressure is not available for a well, find out the accepted rule-of-thumb average hydrostatic pressure gradient for the depth of the zone of interest where the well is located.

==Example of TDS vs. depth==

==Example of total dissolved solids (TDS) vs. depth==

[[file:formation-fluid-pressure-and-its-application_fig5-4.png|thumb|300px|{{figure number|1}}TDS vs. depth plot from southern Arkansas. Copyright: Dickey,<ref name=ch05r6 /> courtesy Chemical Geology.]]

[[file:formation-fluid-pressure-and-its-application_fig5-4.png|thumb|300px|{{figure number|1}}TDS vs. depth plot from southern Arkansas. Copyright: Dickey,<ref name=ch05r6 /> courtesy Chemical Geology.]]