Computer-linked nuclear magnetic logging tool and method having a series

Abstract

The present invention decreases the time needed between collection cycles of an NML tool located in a wellbore penetrating an earth formation by zeroing the effect of prior-in-time residual polarization via a surprising change in the operations, viz., using a series of sham polarizing cycles wherein the coil circuit is permitted to ring at the series Q' values higher than the normal Q value. Result: previously non-precessing components of the residual polarization undergo precession and can be subsequently scattered by the next-in-time field. Since all of the sham fields as well as the next-in-time polarizing field are provided with slow-rising amplitude v. time turn-on segments, the precessing components of the polarization existing at the start of the build-up of the fields are easily scattered. Ultimately, all aspects of the residual polarization is destroyed whereby cyclic NML logging speed can be greatly improved.