Wednesday, March 2, 2016

Nuclear Magnetic Resonance (NMR) Wireline Logging

Nuclear Magnetic Resonance (NMR) tools offer a new and advance physical principal. It refers to the response of atomic nuclei to external magnetic field. Hydrogen proton behaves like a small bar magnet with magnetic moment and angular momentum (spin) which can be aligned and measure its frequency and amplitude signal in the presence of external static field. The signal is proportional to amount of hydrogen in the sensitive volume which can then be calibrated for rock porosity.

NMR logs differ from density and resistivity logs because the NMR measurements provide information only on saturating fluids and are generally lithology independent. The effect of lithology, hydrocarbon, and formation heterogeneity increases the uncertainty in density derived porosities. The technique of using combined NMR and bulk density data  significantly reduces uncertainty in derived logging parameters through elimination of the neutron log. This removes the need to characterize and correcting work for flushed zone fluid densities. (Hamada, 2008).

Reference: Hamada, G.M., Abushanab. 2008. Better Porosity Estimate of Gas Sandstone Reservoirs Using Density and NMR Logging Data. Emirates Journal for Engineering Research.

No comments:

Post a Comment