Key Technique Research Of Dual-Sensor Streamer For Marine Seismic Exploration

Marine oil and gas resources account for about 50%of the global total.The proven global Marine oil reserves are about 54 billion tons.However,the proven degree of Marine oil and gas is much lower than that of land,with huge potential and bearing the hope of the world's future oil.The towed-streamer seismic exploration technology is the main means of marine oil and gas exploration.The traditional towed-streamer is generally equipped with a single type of hydrophone.Each detector is arranged on the same level,so this acquisition method has flexible construction,high efficiency,etc.However,since the towed-streamer works at a certain depth,the acoustic impedance of sea water is greater than that of air,and when the seismic wave propagates upward,total reflection occurs at the sea surface.These sea surface reflections,also known as ghost waves,are also picked up by hydrophone.Every recorded effective reflection wavelet is accompanied by a ghost reflection.Frequency trapping and low frequency energy loss caused by ghost will affect the resolution of seismic records and reduce the effective frequency bandwidth,which greatly restricts the quality of seismic exploration by towed-streamer technology.In order to eliminate the influence of ghost waves,a series of new technologies for towed-streamer have been developed.Among these technologies,the dual-sensor towed-streamer technology is particularly valued because of its simple implementation and effects.Different from the traditional technology,the integrated hydrophone and geophone groups are used in the dual-sensor towed-streamer,and the two detectors are fixed at the same position.The hydrophone detects the change of the hydraulic pressure wave field caused by the seismic wave at the detection point;the geophone records the change of the velocity wave field.By combining the output data of the two detectors,the effective reflection after eliminating the ghost can be obtained.The main research content of this thesis is several key technologies in the dual?sensor towed-streamer system.These technologies are mainly used to guide the actual development.In addition,these technologies can also be used in other systems including many sensors.This paper mainly studies three key technologies:data acquisition,data transmission and system synchronization.In the research of data acquisition technology,this thesis studies the output signal characteristics of hydrophone,geophone and MEMS accelerometer,and the analog output signals of these detectors are digitally sampled with ?-A ADC technology.In the research of data transmission technology,this paper firstly investigates several data transmission technologies commonly used in seismic exploration,and analyzes the increase of the amount of data to be transmitted by dual-sensor towed-streamer system.Combining the existing RS-485 and SerDes technology,a transmission system framework suitable for dual-sensor towed-streamer is proposed.In addition,in order to realize the interaction between multi-streamer data aggregation and host computer,Thunderbolt connection technology is also studied.The research of system synchronization,the command synchronization scheme based on command loop technology,the clock synchronization based on gated multivibrator,and the prototype circuit of gated clock generator are realized.In order to verify the feasibility and reliability of these technologies,a prototype circuit of dual-sensor towed-streamer for key technology testing is built in the laboratory,and the data acquisition system,data transmission link and synchronization performance of the system are tested in the prototype circuit.