Research On Logging Data Encoding And Transmission Technology Based On Signal Channel Prediction Reference Value

The steady increase in oil demand and the continued increase in oil exploitation have led to the development of most oil and gas resources in China in the middle and late stages.At present,the development of oil and gas exploration and development to complex strata requires the rapid transmission of more and more accurate log data.The Logging While Drilling(LWD)system requires timely and accurate acquisition of parameters such as geology and drilling attitude in order to guide the drilling operation.However,it is difficult for the drilling fluid pulse transmission to meet the higher requirements of real-time and anti-jamming performance of logging data transmission.In this paper,the logging data transmission method based on the signal-channel prediction reference value is studied,which has high practical value for improving the real-time reliability of logging data transmission.In order to improve the real-time and reliability of logging data transmission,based on the analysis of logging data characteristics and transmission characteristics,this paper presents the LWD data encoding algorithm and filtering algorithm and designs the frame structure.The main tasks are: based on the characteristics of smooth changes in logging data,the DPCM algorithm is easy to cause error diffusion,the DPCM algorithm is improved,a dynamic segmentation based on the reference value is used to perform coarse and fine quantitative preprocessing.In addition,a variable-length code is used to further compress the data.Considering that the importance of the reference value and the difference value are different,a non-equal protection strategy is used to protect the two types of data respectively.The pulse-space coding is used to protect the reference value.The pulse shifting causes burst errors.The RS code is used to correct the burst error.The differential value plus 1 bit parity bit is used to implement error detection processing.The traditional frame structure is improved and designed separately.Keyframes and non-keyframes transmit two types of data.In order to eliminate interference noise from mud pulse signals,a combination of adaptive filtering and low-pass filtering is used fornoise processing.Noise-free signals are used to filter the algorithm.The effect is verified,and the filtered waveform is identified and decoded using the threshold method according to the characteristics of pulse interval coding.After improved compression performance difference algorithm and error resilience,the RS code error resilience experimental analysis,the results obtained key compression rate and symbol error rate,and improving the reliability of real-time log data.The experimental results show that the compression ratio based on the improved differential compression algorithm can achieve a maximum compression rate of up to40%,and overcome the disadvantages of the error diffusion of the neighbor difference.When the SNR is 6dB,the RS code can achieve better performance.The data reconstruction meets the requirements of real-time and high reliability of the system.