Abstract: An apparatus and methods that can be used to determine various qualitative parameters of an earth formation from nuclear magnetic resonance (NMR) measurements. One embodiment provides a method of NMR-based remote sensing in which a nuclear spins in fluid of interest are encoded while inside an earth formation and then withdrawn into a tool module and analyzed by a sensor located in the tool module. Separate encoding and detection systems may be used, allowing each system to be independently optimized. In particular, because detection of the encoded spins may occur while the spins are inside the detector system, rather than within the earth formation (where they are encoded), the detector system may be constructed to employ a highly uniform magnetic field. This may facilitate various NMR measurements.

Abstract: An apparatus and methods that can be used to determine various qualitative parameters of an earth formation from nuclear magnetic resonance (NMR) measurements. One embodiment provides a method of NMR-based remote sensing in which a nuclear spins in fluid of interest are encoded while inside an earth formation and then withdrawn into a tool module and analyzed by a sensor located in the tool module. Separate encoding and detection systems may be used, allowing each system to be independently optimized. In particular, because detection of the encoded spins may occur while the spins are inside the detector system, rather than within the earth formation (where they are encoded), the detector system may be constructed to employ a highly uniform magnetic field. This may facilitate various NMR measurements.