Numerical Simulation of NMR Logging Tools Antenna

Nuclear magnet resonance (NMR) logging is an advanced method in formation evaluation and oil field production. It can provide the porosity, permeability, bound water volume, free fluid volume and oil viscosity. NMR logging is playing more and more important roles in oil and gas exploitation. The antenna is a core of NMR logging tools. It can transmit the electromagnetic wave and receive the NMR signal. As the NMR logging signal intensity and resolution is influenced by the antenna length, the antenna design is very important for NMR sonde design. The more antenna length is, the more signal intensity is, but the weaker vertical resolution is. In order to optimize the antenna design and accelerate the development of NMR logging tools, a FEM mathematic model of B₁ magnetic field distribution of NMR logging tools is established in the paper. FEM is applied to solve Bi magnetic distribution of NMR logging tools, which can obtain the currency intensity, determine the sensitive zone, and improve the signal intensity and signal-to-noise ratio.