An apparatus and method for NMR analysis of a plurality of core samples includes a core holder (11) that holds a core sample under pressurized conditions. A radio frequency coil (51) disposed about the core holder (11) generates a pulsed-mode magnetic field component over a sample volume occupied by the core sample. A support structure is removably secured to the respective core holder. A permanent magnet (65A, 65B) has an open configuration such that it is removably disposed into a position within the support structure about the radio frequency coil and the core holder. The open configuration allows the same permanent magnet to be used for NMR analysis of a plurality of core samples without the need for depressurizing the respective core holder and disassembling the core holder and corresponding load frame for each core sample. It also allows multiple core samples to be prepared for NMR analysis while separated from the NMR measurement apparatus.