核磁共振测井仪储能电路设计与应用研究

Design and application of energy supply circuit for NMR logging tools

核磁共振测井仪通过发射高能量射频脉冲来实现氢核磁矩的扳转和重聚,并以此获取地层信息。受测井电缆瞬时功率传输能力限制,脉冲发射时直流高压大幅下降,使得扳转角和重聚角不满足要求,无法有效激发氢核。根据核磁共振测井仪射频脉冲特点,在对其能量需求分析的基础上,利用负反馈原理设计一种储能电路,为射频脉冲提供足够功率及稳定的高压输出。在现场应用中,Phi_A及RATIO_B的实时曲线表明该电路能够为射频脉冲发射提供可靠保障。

NMR well logging tools achieve the tipping and refocusing of magnetic moment of hydrogen nucleus through high-energy RF pulse and acquire formation information.Limited to the logging cable instantaneous power transfer capability,DC high voltage is sharply dropped while emitting pulse.So tip angle and flip angle aren＇t satisfactory,which makes it impossible to effectively excite hydrogen nucleus.According to the characteristics of RF pulse of NMR well logging tools,this thesis designs a kind of energy storage circuit to provide enough power and stable high-voltage output for RF pulse,based on the analysis of energy demand and the principle of negative feedback.In the field application,the real-time curve of Phi_A and RATIO_B show that the circuit successfully ensures the RF pulse emission.