A Research And Implementation Of The Data Compression Method For MWD

With the rapid development of LWD(logging while drilling)technology,the data types and quantities of drilling data is becoming more and more big,the precision requirement of drilling data is becoming more and more high.However,due to limitations of data transmission bandwidth and demanding requirements of real-time,real-time transmission of down hole data become the bottleneck of constraint LWD for further development,a single data compression technology has been unable to meet the requirements of large-scale data compression in modern LWD,therefor it is an effective means of combining the data compression by exploring in line with its own characteristics of the data compression method.In this paper,the drilling data curve and precision were studied,the drilling data divided into two categories by analyzing.The first category includes geometry,orientation parameters,underground working parameters,measuring instruments and other parameters,such data variation is more obvious,the data values between adjacent sampling points are very close,and the measurement accuracy is not required of such data,design the DB-LZW algorithm for the characteristics of such data,through the drilling data difference processing and BWT transform and improve the compression efficiency of the LZW algorithm.The second category data includes formation testing and evaluation parameters,such data as logging while drilling core data,measurement accuracy is relatively high(generally measured to three decimal places),so that is a greater amount of the data,and because of the fluctuations of this class data are more obvious,regularity of changes in overall are poor,so this kind of data is compressed by DPCM algorithm,in the distortion does not affect the logging requirements of the premise,to further improve the compression rate while drilling data.Finally,the combination of compression method based on DPCM and DB-LZW algorithm performance testing and analysis by the matlab simulation.Experimental results show that the proposed combination of compression methods,whether in terms of data compression ratio and compression time,have a more significant improvement than a single lossless compression algorithms.