The Design And Excitation Method Of Array Antenna For NMR Logging Tool

By NMR logging,the researchers can not only obtain the basic physical information of porosity,permeability and saturation,but also obtain the information of the viscosity and diffusion coefficient of the fluid,and provide a rich data for the comprehensive evaluation of oil and gas resources.Therefore,the nuclear magnetic resonance logging technology has been widely used.With the continuous deepening of oil and gas exploration and development,people have put forward higher requirements for nuclear magnetic resonance logging tools.Detection space azimuth and antenna array become one of the trends of nuclear magnetic resonance logging tool.At present,the mainstream commercial cable nuclear magnetic resonance logging tool can not realize the exploration of the sector of the well formation.Antenna is an important part of nuclear magnetic resonance logging tool probe,and has an important influence on the detection performance of the probe.This paper analyzes the function and principle of antenna in NMR instrument,and uses numerical simulation software to design the array antenna of the circumferential scan 3D NMR logging tool,and optimize the array antenna from the structure,length and open angle of the array antenna,and make the array antenna and its electric property.The parameters are tested,the rationality and reliability of the antenna are verified by the joint test of the probe with the magnet assembly.The excitation method of the array antenna is explored and the coupling effect between the antennas in the array antenna excitation is avoided by using the relay.