Downhole differentiation of light oil and oil-based filtrates by NMR with oleophilic nanoparticles

A method comprising:

• drilling a wellbore penetrating a subterranean formation using an oil-based drilling fluid that comprises an oil base fluid and a plurality of ferromagnetic oleophilic nanoparticles;
• extracting a plurality of near-wellbore fluid samples from the subterranean formation;
• measuring a nuclear magnetic resonance (NMR) parameter of the near-wellbore fluid samples with an NMR wellbore tool;
• and
• collecting the near-wellbore fluid sample comprising an uncontaminated formation fluid.

A method comprising:

• introducing a wellbore fluid comprising an oil base fluid and a plurality of ferromagnetic oleophilic nanoparticles into a subterranean formation comprising residual oil that comprises light oil;
• performing nuclear magnetic resonance (NMR) measurements on a near-wellbore portion of the subterranean formation;
• and
• determining the residual oil saturation based on the NMR measurements.