Research On Data Processing And Evaluation For LWF Acoustic Logging

Drill-pipe conveying no-cable acoustic logging(LWF)is the new well logging technology in recent years.Acoustic slowness can be used to determine reservoir porosity,identify lithology and gas-bearing reservoir.However,the accuracy of acoustic slowness is low because of the influence of various noise in the actual logging.Researching adaptable data processing method and developing quick automatic acoustic logging data processing software is the most effective approaches to lessen noise of acoustic signal,improve the production efficiency and data reliability.According to SL6000 LWF acoustic logging instrument,this paper analysis its structure,working principle and logging data record format in order to establish requirements of data processing algorithm.The proposed calculating acoustic slowness method combines head wave detecting with slowness calculations on the basis of research situation at home and abroad.First,we solved the problem of baseline drift and looked for the all waveform negative peak,then determined the detecting threshold value by background baseline noise and handled exceptions data by considering the correlation of transmitting time of adjacent waves.Second,we used correlation function to calculate the correlation coefficient between the two waveforms,looked for the position of biggest correlation coefficient and the corresponding slowness,then determined the final slowness according to different correlation.Last,the slowness of common-source and common-receiver is calculated,take the average as the final acoustic slowness.Meanwhile,the software of the data processing for acoustic logging is developed by VC++6.0.It has a lot of functions,including the choice of instrument mode,automatic processing of acoustic slowness,graphing capabilities and the function of output curve data.Practice shows that the method for calculating acoustic slowness makes full use of waveform information,solves the problem of hole diameter change and various noise in the actual logging and improves the resolution and reliability of acoustic slowness,can meet the logging interpreting evaluation of the actual stratum.The software has faithful result of acoustic slowness with fast processing speed.Moreover,the software support various patterns of instruments,including the mode of single launcher and multiple receivers,the mode of multiple launchers and multiple receivers,which can be applied to the data processing of acoustic logging in domestic oil field,has promotional value.