Multi-channel transient electromagnetic inversion method based on footprint technology and transient electromagnetic survey device

Abstract

The invention discloses a multi-channel transient electromagnetic inversion method based on a footprint technology and a transient electromagnetic survey device, and the method can greatly reduce thethree-dimensional inversion space corresponding to a single data point, improves the multi-channel transient electromagnetic three-dimensional inversion efficiency, and comprises the following steps:S1, transmitting a pseudo-random coded current; S2, receiving a pseudo-random response containing geological information; S3, obtaining a ground pulse response; S4, loading an inversion area and meshgeneration model parameters; S5, constructing a minimum parameter functional; S6, constructing a footprint weighting matrix, and constructing a footprint weighting matrix; and S7, obtaining the distribution condition of the geoelectric structure in the inversion area. The device comprises a transmitting probe, a receiver and a working platform.

Description

technical field [0001] The invention relates to the fields of oil and gas resources and geophysics, in particular to a footprint technology-based multi-channel transient electromagnetic inversion method and a transient electromagnetic surveying device. Background technique [0002] Multi-Transient Electromagnetic (MTEM) is a new technology developed in the world since 2002. my country's mineral and oil and gas resources are in short supply, and iron, copper, aluminum and potassium salts are highly dependent on foreign imports, which restricts The sustainable development of the national economy; in view of the serious shortage of mineral resource reserves in my country, "deepening and blind exploration" has become the main battlefield for a new round of resource exploration. [0003] However, as the burial depth of the target increases, the detection environment becomes more complex, and the difficulty of detection increases sharply. Taking into account large depth and high-pr...

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Problems solved by technology

In terms of multi-channel transient electromagnetic data processing and interpretation, the focus is still on one-dimensional inversion and the two-dimensional inversion of the late stage approximate DC method of the upper step wave. There is a lack of a truly effective multi-channel transient electromagnetic three-dimensional inversion method. It is difficult to apply the derivation method to the requirements of actual 3D spatial geological exploration, and it is urgent to carry out multi-channel transient electromagnetic response characteristics and inversion interpretation for complex 3D geological bodies.

[0005] The model parameters and data scale of 3D electromagnetic inversion are very large, and the required calculation and storage requirements are often unbearable for personal computers; this problem is particularly prominent when the multi-channel transient electromagnetic method is used for 3D inversion; one The reason is that the multi-channel transient electromagnetic method often has hundreds of transmitting sources and receivers in a work area. The reciprocity theorem used in traditional MCSEM can effectively minimize the number of sources to achieve the purpose of fast calculation, but the multi-channel transient electromagnetic method The number of transmitting sources and receivers in the variable electromagnetic method is basically the same, so the reciprocity theorem cannot be used to improve the calculation efficiency, resulting in too large a sensitivity matrix, resulting in a high pressure on storage and calculation; the second is that the transient electromagnetic method uses the specific frequency domain The electromagnetic method has a lot more frequency points, resulting in a double increase in the amount of calculation

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