Fluid in the pore space that can flow under normal reservoir conditions. This fluid may include water, oil or gas, and will flow on production, injection or invasion. When the term is used in connection with nuclear magnetic resonance measurements, it refers to the signal that occurs above a certain cutoff, typically 33 ms in sandstones and 100 ms in carbonates. The source of this signal is free water and oil with a viscosity below about 60 cp in sandstones, and 30 cp in carbonates. Note that, contrary to the sense of "free," this oil may or may not be residual under normal reservoir conditions.