Magnet Design and Simulation of Nuclear Magnetic Resonance Logging Probe for Drilling Ship

Abstract

Nuclear magnetic resonance (NMR) logging probe is the core component of drilling ship logging tool, and the performance of magnet directly determines the accuracy of logging data. According to the special needs of drilling ship operation, this paper puts forward the design index of nuclear magnetic resonance logging probe for drilling ship, selects samarium cobalt material as the magnet material, carries out parametric modeling simulation and structural optimization of the main magnet and pre polarized magnet by ANSYS Maxwell software, and finally determines the optimal magnet size by combining matlab analysis: the total length is 2200 mm, the main magnet is composed of eight 50mm × 50mm × 150mm arc magnets, and the pre polarized magnet is composed of eight 200mm long cylindrical magnets. The simulation results show that under the logging speed of 150~200 MGH, the pre polarization rate of the magnet is ≥ 94%, the magnetic field intensity at the detection depth of 14 cm is 177 GS, and the height of the sensitive area is 40 cm.