Drilling Fluids Reference Manual-MAFIADOC.COM
For fresh water,it is 0.433 psi/ft of depth. For water containing 80,000 ppm of dissolved salts (U.S. Gulf Coast),the pressure is approximately 0.465 psi/ft. However,normal marine water is about 35,000 dissolved salts,approximately 0.446 psi/ft. Reservoirs can contain fluids under abnormal pressure up to as high as 1.00 psi/ft of depth.