梯度场核磁共振测井仪电子线路设计

Electronic Circuit Design of Gradient NMR Logging Tool

介绍梯度场核磁共振测井仪控制和采集电路、功率放大电路、Q-转换电路、隔离电路和接收电路等。解决核磁共振测井仪大功率发射和微弱信号检测的技术难题。射频脉冲发射完后,能尽快泄放天线中储存的能量;脉冲发射和能量泄放时可对接收电路进行高压隔离保护。介绍各关键电路的设计原理,并利用所设计的电子线路和自制核磁共振测井仪探头,在实验室条件下对硫酸铜水溶液进行测量,得到满意结果。该电子线路已成功应用于自制梯度场核磁共振测井仪样机,对随钻核磁共振测井仪和井下核磁共振流体分析同样具有重要的参考价值。

Introduced are the principle and specifications of gradient NMR logging tool. Designed are the tool＇s control and acquisition circuit, power amplifier circuit, Q-transfer circuit, isolation circuit, receiving circuit, etc. Solved are the technical difficulties such as high power transmit （up to thousand Watt）, weak signal detection （tens nano-volt to several micro-volt）, quick energy dump after pulse transmitting; the high-power pulses block during the transmitting time and dump time. The design principle and technique of key circuits are introduced and analyzed. Doped water with cupric sulfate is measured with our designed electronics and magnets, which receives ideal experimental result. The designed circuit is not only successfully uses in prototype of gradi- ent NMR logging tool, but also has reference value for LWD NMR logging tool and NMR fluid analysis.