Determining wettability of an oil reservoir using borehole nmr measurements

A method for determining downhole reservoir wettability, comprising:

• acquiring a first set of nuclear magnetic resonance measurements of formation fluids in earth formations at a selected axial depth along a borehole;
• inverting the first set of the nuclear magnetic resonance measurements to produce a first distribution of a spin relaxation parameter for a fluid component in the formation fluids;
• acquiring a second set of nuclear magnetic resonance measurements of a formation fluid sample removed by a formation fluid testing tool at the selected axial depth, the formation fluid sample being kept at a substantially same pressure and a substantially same temperature as those of the formation fluids in the earth formations at the selected axial depth;
• inverting the second set of nuclear magnetic resonance measurements to produce a second distribution of the spin relaxation parameter for the fluid component in the formation fluid sample;
• determining the reservoir wettability from a comparison of the first distribution of the spin relaxation parameter and the second distribution of the spin relaxation parameter.