基于非均匀采样的模拟退火随钻电磁波电阻率测井检波系统研究

在以往的随钻电磁波电阻率测井仪器检波系统中,仪器采样过程大多为均匀采样,检波方法多采用数字相关法或数字相敏检波(DPSD)法,其检波结果往往受采样量化误差以及频谱泄漏影响。针对这一问题,提出一种基于非均匀采样的模拟退火(SA)检波方法,并研制快速检波电路系统,选取基于均匀采样的DPSD检波结果进行对比。结果表明,基于非均匀采样的SA检波方法选频能力强,能更加有效地抑制量化误差相关性以及频谱泄漏带来的检波误差,更适用于恶劣多变环境下的随钻测井仪器检波。

SA demodulation system based on nonuniform sampling for LWD electromagnetic resistivity logging tool

Conventional demodulation systems of LWD electromagnetic resistivity logging use widely uniform sampling, and the measurements are usually processed using digital correlation or the digital phase sensitivity detector(DPSD) method. Consequently, the detection results are affected by the quantization error and the spectrum leakage in the sampling process. In this paper, an simulated annealing(SA) demodulation method based on nonuniform sampling is presented and a rapid detection circuit is designed. The detection results of the proposed method are compared with that of the DPSD methods with uniform sampling, and demonstrate that the former method has a strong frequency-selecting capacity, and the correlation with the quantization errors and the measurement errors brought by the spectrum leakage can both be suppressed effectively. This method is more suitable for demodulation systems of the LWD measurements in extreme environment.