Determination of oil saturation in reservoir rock using paramagnetic nanoparticles and magnetic field

A method of determining a presence, measuring a distribution and saturation or both of an oil or a hydrocarbon or CO2 in a reservoir rock or subsurface formation comprising:

• injecting a fluid comprising one or more paramagnetic nanoparticles coated with a polymer or a surfactant or any combinations thereof into the reservoir rock or subsurface formation to adsorb the one or more coated paramagnetic nanoparticles at an oil/water, gas/water or CO2/water interface, wherein the coated paramagnetic nanoparticles are dispersed in a fluid is selected from the group consisting of water, hard water, brine, and any combinations thereof;
• applying an external magnetic field to oscillate the one or more coated paramagnetic nanoparticles adsorbed at the oil/water, gas/water or CO2/water interface;
• measuring one or more acoustic response parameters generated by the oscillation of the one or more coated paramagnetic nanoparticles adsorbed at the oil/water, gas/water or CO2/water interface, wherein the acoustic response is measured by a device selected from the group consisting of a geophone, a surface acoustic wave sensor, a frequency analyzer, and any combinations thereof;
• and
• determining the presence and an oil, a gas or a CO2 meniscus density in the reservoir rock or subsurface formation to obtain the distribution and the saturation from a frequency spectrum, a magnitude, or a combination thereof of the measured one or more acoustic response parameters.