Layered medium resistivity anisotropy ocean controllable source electromagnetic rapid inversion method

A technology of anisotropy and medium resistance, applied in the field of rapid electromagnetic inversion of layered medium resistivity anisotropy in the ocean, can solve the problems of slow inversion speed and low efficiency, and achieve high efficiency and high inversion speed. fast effect

Active Publication Date: 2020-10-30
OCEAN UNIV OF CHINA
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Problems solved by technology

However, the above methods only invert the resistivity information of the seabed medium, but do not invert the thickness of the seabed stratum. When setting the inversion model, the seabed stratum is set to be divided into multiple thin layers for inversion. The inversion speed is slow and the efficiency is low. Low

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  • Layered medium resistivity anisotropy ocean controllable source electromagnetic rapid inversion method
  • Layered medium resistivity anisotropy ocean controllable source electromagnetic rapid inversion method
  • Layered medium resistivity anisotropy ocean controllable source electromagnetic rapid inversion method

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Embodiment 1

[0048]The invention provides a controllable-source electromagnetic fast inversion method for layered medium resistivity anisotropy. Compared with the traditional inversion algorithm, the algorithm proposed by the invention has the characteristics of fast inversion speed, high efficiency and strong adaptability. At the same time, the inversion method provides a feasible technical means for testing data quality in the field and quickly obtaining inversion interpretation results.

[0049] see figure 1 , a controllable source electromagnetic fast inversion method for layered medium resistivity anisotropy, which mainly includes the following steps:

[0050] S1. Read and convert the ocean controllable source electromagnetic field data involved in the inversion, the data includes electromagnetic field real and imaginary part data, amplitude and phase data, and parameters of the major axis and minor axis of the polarization ellipse.

[0051] According to the user's requirements, th...

Embodiment 2

[0103] In order to verify the correctness of the sensitivity matrix, refer to figure 2 , is a schematic diagram of a typical one-dimensional geoelectric model, assuming that the depth of the resistivity isotropic seawater layer is 10km, and the resistivity is 0.3Ωm. The buried depth of the isotropic high-resistivity thin layer with a thickness of 100m is 1km, and the resistivity is ρ=40Ωm. The resistivity of overburden and bedrock is also isotropic formation, and the resistivities of overburden and bedrock are ρ=2Ωm and ρ=4Ωm, respectively. Assuming that the survey line coincides with the y-axis, 76 transmitters are arranged at equal intervals within the range of 0m-15000m from the survey line, and are all located 50m above the seabed, the transmission frequency is 0.25Hz, the receiving station is located on the seabed, and the coordinates are (x =0m, y=0m, z=10000m). by figure 2 The one-dimensional resistivity isotropy model shown is taken as an example to verify the cor...

Embodiment 3

[0108] This embodiment is the inversion of the resistivity isotropic half-space model. Since there is no subsurface stratification in the half-space model, the influence of formation thickness on the inversion can be removed. Two half-space models are established, assuming that the seabed half-space is an isotropic resistivity medium, and the resistivities are 2Ωm and 40Ωm, respectively. In real geophysical inversion, it is often unknown how many layers of media there are on the seabed, and the number of stratum layers is usually set to be more than the number of real stratum layers. Therefore, the seabed of the initial inversion model is set to 5 layers, and the resistivity and layer thickness of the seabed medium strata (resistivity isotropic inversion), as well as the lateral resistivity, vertical resistivity and layer thickness (resistivity Anisotropic inversion) for inversion.

[0109] In axial viewing mode, a y-oriented horizontal electric dipole source produces a hori...

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Abstract

The invention provides a layered medium resistivity anisotropy ocean controllable source electromagnetic rapid inversion method. The method comprises the steps of reading and converting inversion data; setting inversion execution parameters; setting inversion initial model parameters; constructing an anisotropic resistivity inversion objective function; solving a Jacobian matrix and a Hessian matrix of an electromagnetic field about the anisotropic resistivity; calculating a regularization factor in a self-adaptive manner based on inversion parameter characteristics; solving a model updating amount; calculating an objective function fitting difference of the inversion iteration model; judging whether inversion requirements are met or not; outputting a final inversion model. According to the method, the anisotropic resistivity of a seabed medium and the thickness of a seabed stratum can be inversed at the same time, so that relatively complex seabed stratum distribution can be obtainedby utilizing an inversion model with a small number of layers, and the method has the characteristics of high inversion speed, high efficiency and adaptability to complex geoelectric model inversion.The inversion method provides a feasible technical means for rapidly detecting data quality and obtaining inversion interpretation results in the field.

Description

technical field [0001] The invention relates to the technical field of marine geophysical inversion, in particular to a controllable-source electromagnetic rapid inversion method for layered medium resistivity anisotropy. Background technique [0002] Controlled Source Electromagnetic Method (CSEM) is a marine geophysical exploration method for detecting seabed oil and gas resources and mineral resources. Studies have shown that about 30% of the world's oil and gas resources occur in electrically anisotropic formations, and the electrical anisotropy of the seabed medium is an important factor for obtaining the correct electrical distribution of the seabed medium. If the resistivity anisotropy is ignored in the data, it is very likely that a reasonable seabed geoelectric model cannot be obtained. However, the currently widely used inversion interpretation method is still the traditional geophysical inversion method, which often assumes that the seabed medium is electrically ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01V3/38
CPCG01V3/38Y02A90/30
Inventor 罗鸣李予国裴建新卢杰李卓轩乔荷
Owner OCEAN UNIV OF CHINA
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