深拖式等离子体震源基础研究

The development of deep-towed plasma seismic source can improve the capability of deep sea high resolution seismic survey of our country. It will also become an characteristic deep-towed seismic source technology with own intelligent property, and promote the marine geophysical reseach and resource exploration in deep sea. This proposal aims at the basic problems of deep-towed plasma seismic source development, which refers to the physi-chemical problems of the "electric-plasma-acoustic" process induced by high voltage pulsed discharge in deep water. The computer simulation method and simultaneous detection of electrical signal, optical signal and acoustic signal method are used commonly to study the pulsed discharge load characteristic, plasma characteristic, bubble thermodynamics and dynamics, bubble interaction, and the energy and frequency properties of the wavelet. All kinds of energy losses and the total energy efficiency of "electro-acoustic" energy transition process will also be analyzed. The focuses will be the non-linear variation of pulsed discharge load impedance and the energy decreasing and spectrum changing of the wavelet induced by super high static pressure. Two main technical questions will be answered in this study: whether the pulsed discharge will be inhibited by the super high static pressure or what kind of influence will it has, and what will be the electric design principles generating wavelet with required energy and frequency characteristics in the field of deep sea high resolution seismic survey. Finally, this study will lay the foundation of the technical development of deep-towed plasma seismic source in the next step.

深拖式等离子体震源的研发有助于提高我国深海高分辨率地震勘探技术实力，形成拥有自主知识产权的特色深拖震源技术，大力推动海洋地球物理研究和海底资源的勘探开发。本项目针对深拖式等离子体震源的基础问题，即深水环境下高压脉冲放电的"电-等离子体-声"基础物化问题进行研究，采用模型仿真和"电、光、声"同步测试相结合的方法对高压脉冲放电的电负载特性、等离子体物化特性、气泡热力学和动力学过程、气泡间相互作用过程，以及子波能量和主频特性等参数进行仿真和测试，分析深水环境下电声能量转化过程中的各种损耗和子波能量效率，重点研究深水环境下高压脉冲放电负载阻抗的非线性过程、子波能量损失和主频变化等，解决超高水静压对水中高压脉冲放电的抑制或影响，以及满足深水高分辨率地震勘探所需子波能量和主频特性的电学设计原理等关键问题，为下一步深拖式等离子体震源技术开发奠定基础。

近海底探测可以大大提高探测的分辨率，推动海洋地球物理研究和海底资源的开采。本项目的研究主要针对深拖式等离子体震源的基础问题，即深水环境下高压脉冲放电的“电-等离子体-声”基础物化问题进行多项计算仿真和实验测试工作。各项研究工作按计划执行，包括了实验测试了不同水静压、水温、放电极性、电极参数等条件下的高压脉冲放电的电负载特性、等离子体物化特性、气泡热力学和动力学过程、气泡间相互作用过程，以及子波能量和主频特性等，重点对深水环境下电声能量转化进行了分析。在此基础上，提出了若干解决超高水静压对水中高压脉冲放电的抑制或影响的技术方法，尤其提出了多路延时输出来展宽声脉冲宽度，降低主频的技术方案，并开展了原理性的技术验证。同时也对高压脉冲放电产生的气泡二次发光现象进行了深入研究，为研究空化发光现象提供了新的实验思路。上述结果发表了SCI论文10篇，有2篇论文发表在Applied Physics Letters上，其中1篇被美国物理学会官方杂志physics today专题报告，还有2篇发表在海洋工程著名期刊IEEE Journal of Oceanic Engineering上。授权发明专利4项，其中1项发明专利获得欧盟专利授权。本项目的研究成果已经应用到十三五科技部重点研发计划深水专项2016年启动的第一批项目中“近海底高精度水合物探测技术”项目中，为深拖等离子体震源的研发提供基础数据，设计工作水深达到2000米，是世界首台工作水深超过1000米等离子体震源。