Study Of The Key Technologies Of High-precision Marine Multichannel Seismic Survey

As a rapidly developing subject,high-precision marine multichannel seismicsurvey is not only an important part of the seismic exploration which belonged togeophysical exploration but also a3D observation and survey sustainment system tothe sub-bottom science and detecting techniques.It plays an important role in resourceexploration,sedimentary structure unit demarcation and engineering geological hazarddeteceting,especially in marine oil&gas detecting and hydrate gas survey. Because ofthe long arrangement, big group interval, poor offshore construction flexibility, thetraditional multichannel seismic survey is usually kept at the sea bottom kilometersdeep depth below, general for offshore oil and gas resources detection. Due to highfrequency and poor penetrability, subbottom profiler is normally used for the depth ofthe50m high resolution layer detection, generally for offshore marine engineeringconstruction of geophysical investigation. As a result of the lack of multiple coverageand signal-to-noise ratio, single channel seismograph can’t get velocity data.Therefore, to the marine high precision detection of below50-1000m depth range,present common method can not reach the goals of the geological depth and precision.The marine seismic exploration based on small group interval can make up for thedeficiency of the current methods. The study of key technologies of marine seismichigh precision detection has important significance,because of the foreign exportrestrictions. The papers studies the the key technologies of high-precision marinemultichannel seismic survey, breaks through the high bandwidth large energy plasmasource technology, small group interval high resolution digital towing cabletechnology and improves the accuracy of the exploration, which has achievedsignificant results.Based on the analysis of main marine seismic exploration source, the article getsa conclusion that the spark is the best source for high-precision marine detecting.Dueto the systemic and deep research to the wide,high frequency and high energy sparksource, the article studies the wide,high frequency and high energy plasma sparksource technology with spark electric iron discharge style. The article uses the Onnesequation which is more exact than the ideal gas equation of state to figure the state ofthe air bubble. The article explore the electrode array design principle of the plasmaspark and gets the suitable electrode array style for high precision marine seismicexploration.Aiming at the shortage of the marine seismic tow such as long channelintervel,low distinguishing ability,can not well control, the article analyses the variousunits of a working principle and key technology systemic and forms small channelinterval high resolution digtial tow technology.By means of experiment to contrastand alalyses the tows with same hydrophone combinations and different fillingmedium,the article gets the methods to improve the detecting precision of the seismic tow.The research gets two sets of the high resolution marine multi-channel digtialtow.with independent intellectual property rights.Based on the virtual reflection and the reasons for the formation of multiplewave,the article studies the main structure and identifier methods for the marine smallchannel intervel seismic high precision system to suppress the virtual reflection andthe multiple wave.Base don the systemic analysis to the gathering parameter andmethods of the marine small channel intervel high precision observation system,thearticle gets the field methods suitable for this system.Through the comparison between high-precision marine multichannel seismicsurvey, singlechannel seismograph, subbottom profiler and big arrangementmultichannel seismic survey, the main application range and exploration targets of thehigh-precision marine multichannel seismic survey are discussed. The high precisiondetection method is used to detect temperature salt fine structure for the first time. Byusing "high precision marine seismic exploration data acquisition system" and "highresolution marine seismic exploration multi-channel digital streamer" in the southChina sea, the east China sea, north yellow sea and bohai sea, nearly20000kmseismic profiles are completed.With the study of the high bandwidth large energy plasma source technology,small group interval high resolution digital towing cable technology and the methodsof improving the accuracy of the exploration, the following innovative orbreakthrough are mainly made:(1)The state equation of non-ideal gas-Onnes equation is used to represent thebubbles produced by the source of electric spark for the first time. This equation canbetter reflect the changes of real gas. Source wavelet modelling based on this theory ismore close to the measured signal wavelet.(2)"High resolution marine seismic exploration multi-channel digital streamer"and "high precision marine seismic exploration data acquisition system" aredeveloped, which has high precision, high resolution, flexible working practices andmobility as its outstanding advantages.(3)The results of applications are remarkable. With the use of independentresearch and development, marine geological Survey, engineering geological hazardsurvey and marine resource investigation especially gas hydrate investigation arecarried out. Many suspected BSR shows are found in the investigation of our countrysea area. And the method of seismic exploration is used to detect temperature salt finestructure for the first time."High precision marine seismic exploration dataacquisition system" realize the possibility of penetrating1000m depth stratum with1000m water depth. And frequency of seismic wave can reach1000Hz, the resolutionof the high resolution profile can reach2m, while the highest resolution of superficiallayer can reach1m.