This Technical Note provides a detailed discussion of the benefits of multi-frequency NMR logging. Nearly all modern NMR logging tools have the ability to perform NMR measurements at multiple frequencies during a single logging run. This multi-frequency measurement capability provides many critical operational benefits, including improving the signal-to-noise ratio of the measurements and enabling faster logging (Coates et al., 1999).
Vista Clara’s full line of Javelin and Dart magnetic resonance (NMR) logging probes offer this capability, operating at multiple frequencies to offer the following important benefits:
- Operation in a wider range of wells and boreholes: Multi-frequency logging probes are like having multiple probes in one, so a multi-frequency probe can satisfy a wider range of conditions than any single-frequency probe.
- Faster logging and improved signal-to-noise ratio: Multi-frequency logging improves the time efficiency of data collection by allowing measurements at multiple frequencies to overlap in time. These efficiency gains permit more measurements in the same time interval compared to single-frequency logging. This allows faster logging than a single-frequency system, or improved signal-to-noise ratio for the same logging speed.
- Resilience to EM interference: Multi-frequency NMR logging increases the likelihood of obtaining usable data in environments with high levels of electromagnetic interference (EMI), where single-frequency logging can yield unusable data.
- Multiple Radial Distances: Multi-frequency logging provides independent information at multiple radial distances from the logging probe. This offers the ability to assess borehole conditions and drilling disturbance, thereby offering a quality control metric and process that is unavailable with a single-frequency NMR logging tool.