Basic petrophysical measurements using NMR

Basic petrophysical parameters (porosity, BVI, FFI, CBW and T2 cutoff) are calculated automatically by the LithoMetrix software installed on every GeoSpec from two measurements – one on a cleaned and saturated core plug, the other on the same plug after it has been centrifuged to irreducible water saturation. Each time, the LithoMetrix software generates a pore size distribution, and from these two pore size distributions automatically calculates the basic parameters. The integrated area under the saturated pore size distribution is a measure of the total porosity and is quantified by comparing to a measurement on a porosity standard supplied with the GeoSpec. The area under the distribution after centrifugation is the Bound Volume irreducible (BVI), and the difference in area between these two is the Free Fluid Index (FFI). Clay Bound Water (CBW) is the area under the distribution below a certain preset T2 value, and the T2 cutoff (used for calibrating NMR well logs) is the T2 point at which the cumulative value of the saturated distribution equals the final value of the irreducible distribution.

All of these parameters are calculated automatically by the LithoMetrix software, and the raw data and final results are stored in an internal database for future reference. A pre-formatted report can be generated and printed.

Finally, using either the Coates or Schlumberger model, permeability can be estimated from relaxation data.