The Advantages of Whole Core NMR Measurements

NMR rock core measurements are typically made on core plugs of 1” or 1.5” diameter, and 50 – 60 mm long. However, there are occasions when obtaining normal core plugs is difficult, and it is then preferrable to work on sections of whole core which could be several feet in length. Such samples can cause measurement artefacts due to sections of the sample being outside the sensitive region (Field Of View – FOV) of the NMR probe, resulting in extraneous NMR signals being added to those from within the FOV. It is essential to suppress these extraneous signals otherwise the results of the measurements will be inaccurate.

Suppression of signals from outside the FOV is achieved using a combination of an adiabatic inversion pulse and a slice selective gradient pulse. The gradient pulse ensures that the adiabatic pulse is only applied to nuclear spins within a selected slice, thus eliminating any contributions from out of view signal.

Use of this technique requires a GeoSpec NMR core analyser equipped with pulsed field gradients and GIT Systems Advanced software.

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