Method for estimating formation hydrocarbon saturation using nuclear magnetic resonance measurements

A method for well logging, comprising:

• moving a nuclear magnetic resonance instrument along a wellbore drilled through subsurface rock formations;
• measuring nuclear magnetic resonance properties at a plurality of lateral depths into the formations from a wall of the wellbore;
• corresponding to at least one axial position along the wellbore, estimating a bound water volume, a total porosity and a free water volume at each of the lateral depths from the nuclear magnetic resonance measurements;
• estimating a minimum water saturation at each lateral depth from the total porosity, the free water volume and the bound water volume at each lateral depth;
• estimating a value of water saturation at each lateral depth from the minimum water saturation at each lateral depth;
• determining a relationship between lateral depth and water saturation;
• estimating water saturation at a selected lateral depth greater than the greatest lateral depth of the nuclear magnetic resonance measurements;
• and
• at least one of storing and displaying the estimated water saturation at the selected lateral depth.