Water Resistivity Calculator

Input Parameters

Known Resistivity (Rw1, ohm-m): Range: 0.01–100 ohm-m

Known Temperature (T1): Range: 0–150 °C or 32–302 °F

Target Temperature (T2): Range: 0–150 °C or 32–302 °F

Results

Resistivity at Target Temperature: — ohm-m

Equivalent NaCl Salinity: — ppt

Resistivity at 75°F: — ohm-m

Calculation Method: Uses Arps' formula for temperature correction:
Rw₂ = Rw₁ × (T₁₍F₎ + 6.77) / (T₂₍F₎ + 6.77), where T₁₍F₎ and T₂₍F₎ are temperatures in Fahrenheit.
Salinity approximation: Sₚₚₘ = 3647.5 / (Rw₇₅ ^ 0.955), converted to ppt (Sₚₚₜ = Sₚₚₘ / 1000).
Rw₇₅ is resistivity at 75°F.

Advanced Parameters

Calculation Type:

Known Resistivity (Rw1, ohm-m): Range: 0.01–100 ohm-m

Known Temperature (T1): Range: 0–150 °C or 32–302 °F

Salinity: Range: 0.1–350 ppt or 100–350,000 ppm

Target Temperature (T2): Range: 0–150 °C or 32–302 °F (Optional for Resistivity mode)

Depth (m): Range: 0–10,000 m (Optional)

Temperature Gradient (°C/100m): Range: 0–10 °C/100m

Results

Resistivity at Target Temperature: — ohm-m

Equivalent NaCl Salinity: — ppt

Resistivity at 75°F: — ohm-m

Archie Parameters: a=1, m=2, n=2 (default for Sw calculation)

Calculation Method:
Resistivity to Salinity: Uses Arps' formula: Rw₂ = Rw₁ × (T₁₍F₎ + 6.77) / (T₂₍F₎ + 6.77). Salinity: Sₚₚₘ = 3647.5 / (Rw₇₅ ^ 0.955).
Salinity to Resistivity: Rw₇₅ = (3647.5 / Sₚₚₘ)^(1/0.955), then Rw₂ = Rw₇₅ × (75 + 6.77) / (T₂₍F₎ + 6.77).
Temperature Gradient: If depth provided, T₂ = T₁ + (Depth / 100) × Gradient (°C).
Petrophysical Context: Rw is used in Archie's equation: Sw = (a × Rw / (Rt × Φ^m))^(1/n) for water saturation. Default: a=1, m=2, n=2.