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Calculate Water Saturation From Well Logs

F = Formation Factor

F = c ÷ ( por ^ m )

c = cementation factor
m = cementation exponent
F = 1 ÷ ( por ^ 2 ) (for limestones)
F = 0.81 ÷ ( por ^ 2 ) or 0.62 ÷ ( por ^ 2.15 ) (for sands)

Sw = Water Saturation
Sw = ( F * Rw ÷ Rt ) ^ 1/n
n = saturation exponent
Sw = [ ( c * Rw ) ÷ ( por^m * Rt ) ] ^ 1/n  Constants c = cementation factor (1) m = cementation exponent (1.8) n = saturation exponent (1.8)

 Formation Water Resistivity Rw = Water Resistivity, ohm-m Tm = Rw Measure Temperature, °F R2 = R1 * (T1 + 6.77) / (T2 + 6.77)

 Temperature at Zone Depth (BHT) BHT = Bottom Hole Temperature, °F Calc BHT from Depth and Gradient Depth = feet Temp Gradient = °F per 100 feet (1.5) Temp Surface = °F, mean annual, (50°F) BHT = ( depth * gradient ) + surface temp

 Log Value - Deep Resistivity Rt = Resistivity, ohm-m

 Log Value - Porosity (Choose one of three) Enter % Porosity por = % porosity Calc Porosity from Sonic Delta-T Delta T = sonic travel time (µs/ft) Tma = matrix travel time (51.3 µs/ft) Tf = fluid travel time (188.7 µs/ft) Sonic Porosity = ( Delta T - Tmatrix ) / ( Tfluid - Tmatrix ) Calc Porosity from Bulk Density rho b = bulk density (grams/cc) rho ma = matrix density (2.65 grams/cc) rho f = fluid density (1.0 grams/cc) Density Porosity = ( rho ma - rho b ) / ( rho ma - rho f ) 