Lab based NMR core analysis systems, of which the GeoSpec is the latest, were originally designed to allow petroleum engineers and well log analysts to calibrate the down hole NMR logging data. NMR technology can be affected by changing temperatures, polarity anomalies, and radio signals created naturally and by other electronics equipment. Downhole NMR well log tools work in very dirty, volatile and signal rich environments. As a result, it is very difficult to perform accurate and controlled measurements. NMR well log calibration can assist reservoir engineers and petrophysicists with ensuring the downhole data is interpreted accurately.
Lab based NMR instruments work in a much more clean and controlled environment, so lab based rock core NMR analysis is used to calibrate the data collected by the downhole NMR tools.
The so-called T2 cutoff in a NMR T2 distribution is the T2 value that divides the small pores that are unlikely to be producible from the larger pores that are likely to contain free fluid. The integral of the distribution above the T2 cutoff is a measure of the free fluid (mobile fluid) in the rock. The portion of the curve below the cutoff is bound fluid and is made up of clay bound fluid and the capillary bound fluid. An accurate determination of the T2 cutoff is essential for an accurate determination of recoverable reserves (mobile fluid).
The application of lab based NMR can provide many “reality” checks for the NMR log data analyzers; including more accurate T2 cut offs, which are a key indicator of where the oil or gas is located in a test well.
The data plotting and calculation for this measurement are carried out automatically through LithoMetrix software supplied as the standard operating system for a GeoSpec NMR core analyzer. If you are interested in more information about LithoMetrix or a GeoSpec, please email our sales team.
For more information on how NMR well log calibrations are performed, see the this Application Note.