Research Of Key Technologies For Marine Seismic Exploration Long-cable System

As developing of exploration targets for domestic marine seismic exploration such as deeper purpose rock stratum and more complex geology structure,the scale of current marine towing seismic acquisition system cannot meet the requirements,the research of key technologies for marine seismic exploration long-cable system has been currently becoming the urgent work to do.Oil and gas storage in the China Sea has a wide distribution,from a few hundred meters of shallow to 14km deep.Deeper distribtution leads to more exploration difficulty and need of larger sensor array size.Complex geology structure exploration requires more comprehensive and more abundant seismic data,with support of long-cable system.The latest exploration equipments provided by international well-known seismic exploration instruments and equipments suppliers,such as Sercel and Schlumberger,support exploration technology with more than 12km towline.In addition,research of key technology for marine seismic exploration long-cable system is not only used in the field of offshore oil exploration,can also be applied to other large-scale sensor networks,such as underwater observation network,land mass seismic exploration,etc.This paper mainly brings about research of key techniques for marine seismic exploration long-cable system and research acquivements are directly used to guide system design.Firstly,indictors and requirements of three main technical key points in long-cable system,including data transmission,synchronous data collection and long-distance power supply,were presented based on physical demand of seismic exploration;Then optional scheme and feasibility of high-speed and reliable transmission,system synchronization,long-distance and high-voltage power supply were analyzed theoretically,appropriate implementation method was chosen according to actual needs,and theoretical model was set up to simulate and predict;Next the pre system was designed to verify feasibility of scheme,comparing simulation and actual test,and suggestions with practical value were provided to engineering design of marine seismic exploration long-cable system.Finally system prototype was designed and implemented to make preparation for large-scale application,the prototype system used research aquivements and indicators of prototype were tested.The structure arrangement of article is as follows:The first chapter introduced background of offshore oil exploration,the basic principle of marine seismic exploration and development history and the future developming direction of marine seismic exploration instrument.At the same time,research significance and research content of marine seismic exploration long-cable system were expounded.The 2～4 chapters introduced the research result of key technology for marine seismic exploration long-cable system,including reliable high-speed transmission,system synchronization and high-voltage power supply over a long distance.The second chapter studied how to realize high speed and reliable data transmission of marine seismic exploration long-cable system.First we compared several mature cable transmission ways,such as RS485,Ethernet,SerDes,etc,and emphatically introduced the SerDes technique points like high data rate transmission technology,equalization,pre-emphasis and so on.Data reliable transmission was implemented by designing a two-layer transmission protocol which included fault tolerance mechanism,physical layer using high-speed serial communication with low error rate and protocol layer using byte error information to achieve the position and statistics of error.At last,we verified the reliable transmission protocol on debugging platform and "HAILIANG" system.The third chapter mainly elaborated five-layer synchronization model of marine seismic exploration long-cable system,including synchronization between ships,synchronization between cables,single cable time offset synchronization,clock phase synchronization and clock jitter synchronization,and realization method.First of all,we introduced several kinds of mature synchronization technology,such as GPS,NTP,PTP,and designed proper synchronization scheme according to different levels of system synchronization needs.Then the system synchronization of all levels were simulated and tested actually.The fourth chapter researched long-distance power supply technology of marine seismic exploration long-cable system.First power supply model with line loss was established,the model can evaluate the overall system power consumption and towline terminal voltage under different cable length.Then accuracy of the model was verified according to the measured power consumption of the system data and simulation data,and the possible causes of error were analysed.Finally influence on system power consumption and terminal voltage by parameters,such as power supply voltage,package power consumption and power lines resistance,was analyzed based on the model.Choice of design parameters and meaningful reference were provide according to the simulated system phase diagram.The fifth chapter introduced the design scheme and implementation structure of prototype system,and key indicators,such as harmonic distortion,system noise and crosstalk,were tested.