Study On The Key Technology Of Wide Field Electromagnetic Sounding Instrument

The wide field electromagnetic sounding method is presented by academician He Ji-shan. He puts a theoretical innovation based on the existing CSAMT arming at weak signal caused by measurement in remote area and sending and receiving frequency one by one, associated with pseudo-random signal method which is an ideal source of electromagnetic exploration because of the near amplitude and homogeneous distribution in logarithmic scale of primary frequencies. Wide field electromagnetic method inherits the advantage of controlled source in CSAMT, then overcomes the shortcomings of random source and weak signal in MT. It doesn't continue to use "cagniard apparent resistivity" formula, but use accurate formula of electromagnetic field to extract the apparent resistivity by iteration method to measure in non-remote area, greatly expands exploration range of controlled sources electromagnetics, and has an improvement on the observed speed, accuracy and efficiency of field exploration. Wide field Pseudo-random signal electromagnetic method is a new and unique electromagnetic method for exploring.Wide field pseudo-random electromagnetic sounding system was based on wide field electromagnetics sounding method, broke through some outdated concepts on thoughts and principles of design, broke down the foreign domination on electromagnetic instruments. It realized innovation independently and held independent intellectual property rights,which would promote the further development of electromagnetic instruments.The apparent resistivity of wide field electromagnetic sounding method can be achieved by measuring any component of the electromagnetic field, but the measurement of the horizontal component in the electric field is relatively simple. The paper researches sounding systems based on E-Ex wide field electromagnetic sounding method which integrates the hot technologies of the modern electromagnetic instruments and includes high-power pseudo-random signal transmitter and receivers for 3D EM exploration in the deep hydrocarbon reservoir, According to the theory of pseudo-random signal, the paper discusses the generating principle of pseudo-random signal waveform and the design of transmitting controller corresponding, probes the power design,, high power rectifier and filter, and inverter technology of transmitter in detail, designs the Matlab models on rectifier, filter and IGBT inverter of 200KW power, then simulates and analyzes it, describes the design of IGBT's drive and passive lossless buffer, achieves the detection of over-voltage or over current and protection of IGBT, analyzes the wasted power of high-power semiconductor devices used in transmitter, and ensures reliable operation of transmitter by using the new heat pipe cooling technology for power semiconductor cooling.The paper analyzes the frequency and amplitude of effective signals and interference in E-Ex wide field electromagnetics, probes analog and digital frequency selection technology, realizes coherent detection based on GPS synchronization, proposes digitizing the receiving signal, deduces the process of the extraction of pseudo-random multi-frequency signal, and simulates and analyzes it in Matlab, and then achieves the extraction in DSP processor, designs low-noise precision analog signal conditioning circuit and high-speed, high-resolution analog-digital conversion, describes the core system based on TMS320C6713 DSP and network communication interface and data acquisition interface and the GPS interface, achieved software functional design and programming of DSP, proposes and achieves network communication system based on optical fiber and wireless network communication system based on Canopy, which can realize 3D exploration of wide field electromagnetics.Index tests indoor using resistor network of receivers (such as consistency and stability) and field tests in oil region of wide field electromagnetic sounding system (including 200KW transmitter and receivers) have shown that the system has achieved the prospective specifications, basically meets the requirements of 3D EM exploration, and provides the necessary condition for realizing and popularizing wide field electromagnetics, which has important practical significance.The paper won the funding of National Natural Science Foundation Project:Special Fund in Scientific Instruments Basic Research "the basic research of wide field electromagnetic sounding system (40827002) ".