Wide Area Electromagnetic Survey

- Apr 10, 2019-

“The exploration of 300,000 km away's lunar and the deepest ocean the Mariana Trench exploration have been achieved. The deep well detection of 13,000 km has not been realized in the world, because the deep rock is hard and complicate, it's extremely difficult to detect deeply. However, we have been able to detect a depth of 8,000 meters underground and are heading for a target of 13,000 kilometers." On the 7th, the application of geophysicist and academician of the Chinese Academy of Engineering, He Jishan, told the Science Technology Daily.

The "three deep" exploration in the deep sea, deep land and deep space is the high point of scientific research that the world is competing for. He Jishan is the most "drilling" person in the field of deep exploration in the world. For decades, do “CT” for the Earth, and the team of He Jishan won the “skills” of “exploring the ground” up to 8,000 meters.

At the National Science and Technology Awards Conference on January 8, the project "Deep Depth, High-Precision Wide-area Electromagnetic Exploration Technology and Equipment" wons the first prize of the 2018 National Technology Invention Award.

Find the exact solution and do "CT" for the deep part of the earth.

Under the application of wide-area electromagnetic exploration technology and equipment, it has helped China find many underground resources: up to now, it has submitted more than 300 billion shale gas resources, more than 100 billion geological reserves, and 186 million tons of conventional oil and gas reserves. The biogas reserves of 8 billion yuan will release more than 20 million tons of coal resources, and the potential economic value will exceed 1.5 trillion yuan.

According to He Jishan, deep physical exploration relies on ground devices to “see through” the Earth. At present, the perspective of the Earth is to make a "B-ultrasound" to the Earth through sound waves. The second is to use the electromagnetic waves to make "CT" to the earth. Among them, the application of electromagnetic method has been more than 100 years old. However, due to the complex and variable excitation conditions, initial conditions and boundary conditions of the electromagnetic method, the exact solution of the Earth's apparent resistivity equation is difficult to obtain.

Previously, Canadian scholar Goldstein obtained the approximate solution of "apparent resistivity parameter" by simplifying the electromagnetic wave equation to the plane wave equation, and created the "controllable source audio magnetotelluric method" for determining the underground resistivity by artificial source electromagnetic method. CSAMT method). This method monopolizes the global artificial source frequency domain electromagnetic law market for nearly half a century. However, the approximate solution also "limits" the depth of detection of the CSAMT method only within 1500 meters underground. As the depth increases, the error applied by the method increases, and the resolution and accuracy also decrease drastically. To achieve the deep, precise and accurate "deep ground detection", there are huge challenges in the three aspects of method theory, detection technology and instrumentation.

He Jishan obtained the exact solution of the electromagnetic wave underground propagation equation and created a new electromagnetic exploration theory with wide-surface electromagnetic wave as the core. The method transmits an alternating electromagnetic field of different frequencies to the underground through an artificial current source, and can observe one or more electromagnetic field components in a large underground area, calculate a wide-area apparent resistivity, and detect a geological target with electrical differences. Based on the theory of detection technology and self-developed instrumentation, the detection depth can reach 5 times that of the CSAMT method.