| Spontaneous potential (SP) || 6–10 ft || N/A || Well-to-well correlation, estimate ''R''<sub>w</sub> , and indicate [[permeability]] || Does not work in oil-based mud and ''R''<sub>mf</sub> and ''R''<sub>w</sub> must contrast | | Spontaneous potential (SP) || 6–10 ft || N/A || Well-to-well correlation, estimate ''R''<sub>w</sub> , and indicate [[permeability]] || Does not work in oil-based mud and ''R''<sub>mf</sub> and ''R''<sub>w</sub> must contrast |