Chemically-selective imager for imaging fluid of a subsurface formation and method of using same

A method of imaging fluid positioned in a subsurface formation, the method comprising:

• positioning a core sample of the subsurface formation in a passage of an imager in a downhole tool;
• flooding the core sample by passing fluid from the formation into the passage;
• imaging the flooded core sample by:
• directing a magnetic field through the passage in a direction along the longitudinal axis of the passage;
• selectively directing a gradient field through the passage;
• selectively pulsing a radio frequency field through the passage in a direction orthogonal to the longitudinal axis of the passage;
• and
• generating images of the fluid in the core sample during the pulsing whereby images of hydrocarbons and aqueous fluids in the core sample are generated based on differences in chemical shift, wherein nuclear magnetic resonance measurement is performed using compressed sensing and rapid acquisition with relaxation enhancement (RARE).

A method of imaging fluid positioned in a subsurface formation, the method comprising:

• positioning a core sample of the subsurface formation in a fluid filled passage of an imager;
• directing a magnetic field through the passage in a direction along a longitudinal axis of the passage;
• selectively directing a gradient field through the passage;
• directing a radio frequency field through the passage in the direction orthogonal to the longitudinal axis of the passage;
• selectively acquiring nuclear magnetic resonance measurements of the fluid in the core sample by selectively pulsing frequencies of the radio frequency field to the core sample and applying the gradient field to the core sample according to a pre-determined k-space sampling plot;
• and
• generating images of the fluid in the core sample during the pulsing whereby images of hydrocarbons and aqueous fluids in the core sample are generated based on differences in chemical shift, wherein the selectively acquiring nuclear magnetic resonance measurement is performed using compressed sensing and rapid acquisition with relaxation enhancement (RARE).