Abstract
Surface nuclear magnetic resonance (NMR) can measure subsurface hydrogeological information, such as saturated porosity, without drilling, making it a very attractive geophysical method for aquifer characterization. But the method often suffers from a low signal-to-noise ratio, and consequently, long data acquisition times due to excessive measurement stacking.
Recently, steady-state sequences were introduced to surface NMR and can yield high quality data in a short time. In addition to faster acquisition, steady-state surface NMR purports to measure the transverse relaxation time T2, which is correlated with hydrogeological parameters like pore-size, unlike the effective transverse relaxation time T2* associated with standard single pulse measurements. This ability to isolate T2 enhances the value and robustness of hydrogeological interpretations from the NMR parameters.
While previous studies suggest that steady-state measurements have enhanced sensitivity to T2, a ground-truth validation has not yet been done. We compare steady-state surface NMR results against borehole NMR logs as ground-truth. In line with previous studies of other sequences, we find that steady-state surface NMR also struggles with short relaxation times. For relaxation regimes of T2 > 10 ms, reliable profiles can be obtained from steady-state data, provided the assumption of homogeneous horizontal layers is valid. However, even in more complex geological environments, steady-state surface NMR delivers representative estimates of T2.
Recently, steady-state sequences were introduced to surface NMR and can yield high quality data in a short time. In addition to faster acquisition, steady-state surface NMR purports to measure the transverse relaxation time T2, which is correlated with hydrogeological parameters like pore-size, unlike the effective transverse relaxation time T2* associated with standard single pulse measurements. This ability to isolate T2 enhances the value and robustness of hydrogeological interpretations from the NMR parameters.
While previous studies suggest that steady-state measurements have enhanced sensitivity to T2, a ground-truth validation has not yet been done. We compare steady-state surface NMR results against borehole NMR logs as ground-truth. In line with previous studies of other sequences, we find that steady-state surface NMR also struggles with short relaxation times. For relaxation regimes of T2 > 10 ms, reliable profiles can be obtained from steady-state data, provided the assumption of homogeneous horizontal layers is valid. However, even in more complex geological environments, steady-state surface NMR delivers representative estimates of T2.
| Originalsprog | Engelsk |
|---|---|
| Publikationsdato | 9 dec. 2024 |
| Status | Udgivet - 9 dec. 2024 |
| Begivenhed | AGU Fall meeting 2024 - Washington DC, USA Varighed: 9 dec. 2024 → 13 dec. 2024 |
Konference
| Konference | AGU Fall meeting 2024 |
|---|---|
| Land/Område | USA |
| By | Washington DC |
| Periode | 09/12/2024 → 13/12/2024 |