Research On Key Technologies Of Towed Seismic Resource Exploration System

With land seismic resource explorations moving forward to the regions with harsh natural environment,using the widely-used cable seismic exploration system leads to low operation efficiency and high labor cost,thus it becomes hard for the cable systems to meet the requirements of seismic exploration equipment in land seismic exploration.High efficiency and automation have been the development trends for modern land seismic resource exploration equipment.In line with the development trends,focusing on the research and development of towed seismic exploration system,key technologies including arrayed geophone auto planting,high-precision low-cost data acquiring unit(DAU)positioning,high-precision seismic data acquisition synchronization of multi DAUs,efficient reliable wireless data transmission and single channel seismic data compression have been studied with novel ideas and methods,and the experiments have been carried out and shown the feasibility of the proposed ideas and methods.The main research contects are summed up as follows:(1)The towed seismic data acquisition unit has been developed,with the functions including seismic data acquisition,DAU differential positioning,wireless data transmission and arrayed geophone auto planting,exempting manual geophone planting and manual DAU positioning in the on-site operations,and achieving the seismic data acquisition with low noise and the long-term seismic data acquisition synchronization of multi DAUs simultaneously.Based on the geophone array theory and the research on the extra interference in channel iron autojuggie,the arrayed geophone auto planting mechanism has been designed,achieving the geophone auto planting without extra interference and the noise suppression based on geophone array.The novel method has been proposed for synchronized seismic data acquisition,using GPS pulse per second to trigger the synchronized start and generating the acquisition clock signal based on GPS pulse per second by frequency multiplication,the circuits have been designed and the long-term seismic data acquisition synchronization of multi DAUs has been achieved with the precision of 100 ns level.Based on the carrier phase differential positioning principle,the method has been designed processing the carrier phase differential positioning calculation in the proposed DAU,achieving low-cost DAU self-positioning with the precision of subdecimeter level.(2)Wireless seismic data transmission in seismic exploration has been stuided.The duallayer wireless data transmission network structure using Wi-Fi and LTE has been designed.The alternate usage circuit with dual flashes has been designed with the quasi real-time seismic data transmission strategy,making the proposed DAUs able to transmit seismic data during the seismic data acquisition and storage,thus the proposed DAUs are able to execute quasi realtime seismic data transmission.To meet the demand of quasi real-time seismic data transmission,the gateway node has been designed.On account of the features of the wireless network,the reliability mechanisms have been designed.The wireless DAU array integrity mechanism has been designed to make DAUs influenced by exceptions able to regain the data exchange with the center station in short time;the quasi real-time transmission coordination mechanism and the congestion control mechanism have been designed to make reduction on conflict and congestion.The seismic data transmission experiment has been executed using the proposed dual survey line acqusition array including 72 DAUs,and the result shows that the proposed system can achieve quasi real-time seismic data transmission;for 4000 sps 32-bit sampling seismic data acquisition of 60 s using the proposed array,the extra data transmission time consumption was less than 1 s.(3)For the improvement on seismic data transmission efficiency for the DAUs transmitting seismic data after the acquisition and storage operation,the exploratory research on high-fidelity data compression algorithm for single channel seismic data of DAU has been conducted.Based on the FFT fast matching pursuit(FFT-MP)algorithm,the segmented FFTMP structure has been proposed,and the modified Morlet wave atom dictionary has been proposed to replace the constantly-used zero-phase Ricker atom dictionary.The simulation experiment shows that with the same fidelity requirement,the proposed algorithm makes improvements in compression ratio and time consumption comparing to FFT-MP using the zero-phase Ricker atom dictionary;with the fidelity requirement of 20 d B,the single channel seismic data generated by 4000 sps 32-bit sampling acquisition of 60 s can be compressed to less than 3000 bytes in less than 10 s using the proposed algorithm,and the result shows that the proposed algorithm can decline the data volume effectively and raise the overall efficiency of seismic data transmission.