Research On Power Supply Technology For Long Streamer In Deep Sea Seismic Exploation

With the strategic goal of China's maritime power,deepwater oil and gas exploration and development has become the focus of marine exploration in the future.Seismic exploration is the most commonly used technical means in marine exploration,and the length of marine seismic exploration streamer affects the depth of exploration strata.The length of the leading marine exploration equipment abroad is above 12km,while the length of the streamer independently researched and developed by China can only reach 7km(The track spacing is 3.125m).With the target of marine exploration towards deep water and deep strata,it is urgent to develop long streamer system.suitable for deep-sea exploration.The length of marine seismic exploration streamer is closely related to the parameters of the power supply network of underwater data acquisition and transmission system.The power supply network of underwater data acquisition and transmission system is usually powered by high voltage direct current(HVDC).The power supply voltage is 360V-400V.The high voltage power supply transmits direct current to each acquisition transmission node(digital package)from near to far through the power cable.The high voltage to low voltage module(DC-DC module)on the node converts high voltage to the low voltage required for the board operation,typically 5 V or 12 V.As the size of the detector array increases and the length of the streamer increases,the output current of the high voltage power supply increases.When the length of the streamer increases to a certain value,the power supply on the ship enables overcurrent protection and automatically disconnects the output,which results in the system unable to work.The output voltage of the high voltage power supply,the resistance of the power cable,and the power consumption of the acquisition transmission node are the main factors that restrict the effective power supply of the streamer.On the basis of studying the power supply network of the underwater data acquisition and transmission system of long streamer for deep sea,we establish the voltage distribution model,and solve the nonlinear equations established by the model precisely.We build a test platform of 1500 meters in the laboratory and compare the theoretical value of voltage solved by the model with the tested value of voltage.The experimental results prove that the model is accurate.Based on the correct model,the paper simulates and analyzes three key factors affecting the length of the streamer.After theoretical calculations,we have determined the system parameters that can power 15km streamer effectively,including the output value of the high voltage power supply,the resistance of the transmission power line,and the power consumption of the digital package.The parameters are used to guide the design of long streamer.The paper also studies the effect of the boost converter on the underwater power supply network,and solves the voltage distribution model with the boost converter,and verifies the correctness of the model with boost converter after laboratory testing.When there are multiple boost converters in the long streamer system,the position of the boost converters is optimized by genetic algorithm.The simulation results show that adding the appropriate amount of boost converters can effectively increase the length of the streamer.Finally,the paper introduces the design of low-power underwater data acquisition and transmission hardware circuit in the long cable system in detail,and on the basis of selecting low-power chip and optimizing part of the algorithm,the power consumption of acquisition and transmission circuit of the digital package is 1.5W,which reaches the design target to support 15km effective power supply(the target requirement is less than 2W).We conduct relevant experiments based on low-power digital package,including function test and power consumption test of digital package,1500-meters test platform experiment and so on.In addition,the paper also puts forward the improvement directions that can be continued to be studied in the future,which is instructive for the follow-up work.