Robust data smoothing algorithms and wavelet filter for denoising sonic log signals

Abstract

Well logging is an essential approach to make geophysical surveys and petrophysical measurements. It plays a key role in interpreting downhole conditions. But, well logging signals usually contain noise that distort results and causes ambiguous interpretations. In this paper, the wavelet filter and robust data smoothing algorithms are tested for denoising synthetic sonic log and field sonic log data. Robust data smoothing algorithms include Gaussian, RLOESS (Robust locally estimating scatterplot smoothing), and RLOWESS (Robust locally weighted scatterplot smoothing) methods. Uniform and normal distribution noise applied to synthetic model. Results revealed that the wavelet filter performs better than data smoothing algorithms in denoising uniform distribution noise. However, the RLOESS removed uniform noise acceptably. But, for normal distribution noise, the wavelet filter disrupts and data smoothing algorithms, specifically RLOESS attenuated noise perfectly. Due to the noise nature of field sonic log data, wavelet filter completely disrupts, but data smoothing algorithms removed the noise of field data more efficiently, particularly RLOESS. So, it can be stated that the RLOESS is a perfect algorithm for denoising sonic log signals, regardless of noise nature.