Analysis and design of magnet and antenna for NMR well-logging tool

We analyze the performance of a saddle-point nuclear magnetic resonance (NMR) well-logging tool proposed by Kleinberg, Sezginer and Griffin (1992). A perturbation technique in conjunction with the finite element method (FEM) is used to evaluate the antenna efficiency. The static magnetic field due to a permanent magnet in the presence of ferrites is evaluated by using nonlinear magnetostatic FEM. Comparisons of the computed and measured results indicate a very good match. The present approach has proved to be quite efficient and accurate in the design of an NMR sensor. A typical inside-out NMR tool for oilfield measurement is shown.