Resarch On The Seismic While Drilling

The research on Seismic While Drilling Technique (SWD), collaborating with the Major Program "Advanced Drilling Techniques and Equipments", supported by the National High Technology Research and Development Program of China (863Program).SWD is regarded as a difficult problem publicly in the world, resulting from the weak, random and continuous drill-bit signal, and the noise is very strong from drilling machines in the field. The wave field is complicated and the signal is difficult to process. Underlying the previous researches and documents from many countries, studied the SWD basic theory, explored the principle, the characteristics and the relevant factors of drill-bit signal, researched the wave propagation, and supported the essential base for the SWD monitoring and signal processing.According to the characteristics of the drill-bit signal, and the observing and measuring techniques for earthquake and geophysical prospecting, we building an innovative data acquisition instrument for SWD, and developing a system for monitoring SWD on-site quality, and an experiment of SWD on-site monitoring is achieved. Therefore, the monitoring data is collected with great quality for develop the SWD data processing technique.In this thesis, analyzing the property of the noise in the drilling field, the periodicity and spectrum of the drilling noise are gained, and put forward a new method with the difference of the periodicity between effective signal and noise to increase the signal to noise ratio (SNR). Furthermore, the window-shifting wavelet transform in the correlation domain is used to analyze the periodicity of the SWD signal, and expanded to a denoising technique based on the periodicity and independence of the signal.Studied on deconvolution techniques such as band-limited multi-channel statistical deconvolution, blind deconvolution and so on, they are developed to limit the multiple reflected waves and to improve data resolution, and applied to process the SWD data.Developing a new technique based on the blind-source location theory, calculating interval velocity with wave equations and time delay, and obtaining the SWD interval velocities with high resolution for the application of S WD.Based on the different characteristics of wave propagation between SWD effective waves and special noises from the drilling field, experiencing plenty of field experiments and field data processing and analyzing, a new method is proposed for separating the SWD wave field with the propagation property. By this method, SWD records with high SNR are gained, and can be used to detect and extract the drill-bit signals from the original records. This solves a technically difficult problem in the SWD.By studying high-rate loading events in drilling progress, three methods with searching SWD effective waves for loading events are proposed, and developed a technique for searching SWD event signal, which improves the efficiency of analyzing SWD data.By researching the methods for the reference signal reconstruction from the data recorded at surface, a technique is developed for reconstructing the reference signal, breaks the rigorous limit for the reference signal in the traditional SWD data processing techniques, and simplifies the acquisition and processing system for the SWD data. Furthermore, processed the SWD RVSP with the field data, and obtained the CDP stacking profiles with high SNR.