Array Waveform Interference Processing Method For Cased Hole And Seimoelectric LWD

Acoustic logging is an important logging method in the field of petroleum exploration.The use of acoustic logging in cased hole detection and logging while drilling has been a hot issue,and has been widely used in commercial oil and gas exploration.But in the free casing well logging and logging while drilling,due to the presence of large casing and drill collar,when motivated by the acoustic source,there will produce the tube wave(casing wave and drill collar wave)along the casing and drill collar.The strong disturbance of tube wave makes it difficult for us to extract the information of formation.Therefore,the problem of casing filtering and the sound insulation problem of drill collars are becoming more and more important.At present,the method of waveform interference,dual source excitation and other methods are used to deal with the interference of casing wave in the casing well logging.In the process of dealing with the drill collar wave interference of logging while drilling,there are many methods,such as the drill groove,the electric effect and the dual source excitation method.The method of waveform interference is a kind of method to extract the information of formation,which is known as the tube wave character,and the tube wave and the formation wave are excited by the same source.In this paper,the waveform interference method is used to deal with the theoretical simulation data of free casing well logging and LWD.This paper first introduced the theoretical model and formula of free casing well logging and seimoelectric LWD,and then expounds the theories and promotion of waveform interference method,and briefly introduces the array waveform processing tool-slowness time correlation method(STC).After processing theoretical simulation data of free casing well logging using the wave waveform interference method,and combining with the slowness time correlation method,we found that this method can effectively weaken the casing wave,and significantly enhance the signal-to-noise ratio and correlation of stratigraphic information.Then using this method to process theoretical simulation data of seimoelectric LWD,in this part,we only processed the dual-source-excitation electric-field waveforms which are still residual collar wave.Through inspect two different fast formation,we found the collar wave was obviously suppressed,and the signal-to-noise ratio and correlation of stratigraphic information was significantly enhanced.The results show that the method can be applied to the casing filter of free casing well logging and the drilling collar filtering of dual-source-excitation seimoelectric LWD.If the array coupled waves excited by the same source,the waveforms are not dispersion or weaken dispersion,and the characteristics(time and velocity)of one waveforms are known,we can apply this method to extract velocity information of the waveforms which are covered up.This method has some guiding significance for the special time domain waveform processing.