CN111880235B - Ocean electromagnetic formation anisotropic resistivity and emission source posture joint inversion method - Google Patents

Abstract

The invention provides a joint inversion method of anisotropic resistivity and emission source attitude of a marine electromagnetic stratum, which comprises the following steps: reading and converting ocean controllable source electromagnetic field data participating in inversion; setting a joint inversion execution parameter; establishing an observation system and designing a joint inversion initial model; constructing an anisotropic resistivity and emission source position parameter joint inversion target function; solving a jacobian matrix and a hessian matrix of parameters of the electromagnetic field, which are related to the anisotropic resistivity and the position of the transmitting source; adaptively calculating a regularization factor based on the inversion parameter characteristics; calculating the model updating quantity; calculating a target function fitting difference of the inversion iteration model; judging whether inversion requirements are met; and outputting the final inversion model. The method considers the influences of the resistivity anisotropy of the seabed medium and the position and attitude parameters of the emission source on the inversion result, can effectively solve the influence of the inaccurate position and attitude parameters of the emission source on the interpretation of the electromagnetic data of the marine controllable source, and has wider applicability and stronger fault tolerance.

Description

Joint inversion method of anisotropic resistivity and emitter attitude in marine electromagnetic strata

technical field

The invention relates to the technical field of marine geophysics of multi-parameter joint inversion, in particular to a joint inversion method of the anisotropic resistivity of the marine electromagnetic formation and the attitude of the emission source.

Background technique

Controlled Source Electromagnetic Method (CSEM) is a marine geophysical exploration method for detecting seabed oil and gas resources and mineral resources. With the increasing demand for resource development and deep exploration, marine electromagnetic methods are playing an increasingly important role in the investigation of mineral resources and the study of the structure of the oceanic crust and mantle. The frequency-domain marine CSEM method usually uses a horizontal electric dipole source towed tens of meters above the seabed as the emission source, and transmits low-frequency electromagnetic signals in the range of 0.1-10Hz to the electromagnetic acquisition station during the process of being towed by the scientific research ship. The electrical distribution of the seabed medium is obtained by inverting the electromagnetic signals received by the collection stations on the seabed surface. The strength and quality of electromagnetic signals received by the electromagnetic acquisition station are not only related to the resistivity of the seabed medium, but also directly related to the relative position and attitude parameter accuracy of the transmitting source and receiving station. In the actual offshore operation, it was found that the launch source was affected by factors such as seawater movement and ship speed instability during the process of towing the launch source by the research ship, so that the launch source could not move forward according to the preset path, and its position and attitude parameters would appear larger. The fluctuation of the range, and this kind of change is difficult to be monitored and recorded, resulting in the deviation of the position and attitude parameters recorded by the emission source from the actual ones, and the inaccurate position and attitude data of the emission source for the processing and inversion interpretation of marine electromagnetic data posed great difficulties. Therefore, it is necessary to calibrate the position and attitude parameters of the transmitting source to improve the quality of marine electromagnetic signal data.

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 isotropic when inverting marine electromagnetic data obtained from marine resource exploration. The inversion method may provide inversion results with huge errors for later data interpretation, which may also lead to wrong interpretation results. For this reason, the nature of the resistivity anisotropy of the seafloor medium must be considered when interpreting oceanographic electromagnetic data.

In the existing inversion methods, the influence of the position and attitude parameters of the electromagnetic emission source on the inversion results is rarely considered. Most of the methods directly use the electromagnetic emission source parameters with errors for inversion, and the inversion results must also have error. Therefore, if an inversion interpretation method that effectively corrects the position and attitude parameters of the electromagnetic emission source can be proposed, the accuracy of electromagnetic data interpretation will be effectively improved.

Contents of the invention

The purpose of the present invention is to provide a combined inversion method of the anisotropic resistivity of the marine electromagnetic formation and the attitude of the emission source, which can be applied to the accuracy of marine electromagnetic detection and inversion interpretation.

In order to achieve the above object, the present invention provides the following technical solutions:

1. A joint inversion method for the anisotropic resistivity of the marine electromagnetic formation and the attitude of the emission source, characterized in that it mainly includes:

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 polarization ellipse major axis and minor axis parameters;

S2. Setting joint inversion execution parameters, said parameters including inversion maximum number of iterations, target fitting difference, maximum iteration step size, step size ratio coefficient, penalty function type, and regularization attenuation coefficient;

S3. Establish the observation system and design the initial joint inversion model;

S4. Constructing an objective function for joint inversion of anisotropic resistivity and emission source attitude parameters;

S5. Calculating the Jacobian matrix and the Hessian matrix of the electromagnetic field about the anisotropic resistivity and the attitude parameters of the emission source;

S6. Adaptively calculate the regularization factor based on the characteristics of the inversion parameters;

S7. Calculating the update amount of the anisotropic resistivity and the attitude parameter of the emission source;

S8. Calculate the fitting difference of the objective function of the inversion iterative model;

S9. Judging whether the inversion requirements are met, if so, turn to S10, and if not, turn to S5;

S10. Outputting the final inversion model.

2. the method for joint inversion of the anisotropic resistivity of the ocean electromagnetic formation as claimed in claim 1 and the attitude of the emitter, is characterized in that, the joint inversion objective function of constructing the anisotropic resistivity and the attitude parameter of the emitter is:

为模型参数向量的梯度；||·||为标准差算子；d为反演使用的观测数据向量；W_d为数据加权矩阵；W_m为模型加权矩阵；F(m)表示模型m的正演响应算子；μ_ρ、μ_p和μ_T分别为反演模型中海底各向异性电阻率参数m_ρ、发射源位置参数m_P和发射源位置参数m_T的正则化因子。In the formula, φ is the objective function of the inversion algorithm; m is the model inversion parameter vector, which includes the seabed anisotropic resistivity parameter m _ρ , the position parameter m _P of the emission source, and the attitude parameter m _T of the emission source, that is, m =m _ρ +m _P +m _T ;

is the gradient of the model parameter vector; ||·|| is the standard deviation operator; d is the observed data vector used in the inversion; W _d is the data weighting matrix; W _m is the model weighting matrix; Forward modeling response operator; μ _ρ , μ _p and μ _T are the regularization factors of seabed anisotropic resistivity parameter m _ρ , emitter position parameter m _P and emitter position parameter m _T in the inversion model, respectively.

3. the joint inversion method of the anisotropic resistivity of marine electromagnetic stratum as claimed in claim 1 and emitter attitude, is characterized in that, described self-adaptive regularization factor is determined according to the following formula:

_In the formula, i represents the i-th _inversion iteration; μ _i is the regularization factor _; Max|·| is the element with the largest absolute value of ^the matrix; ]; M is the dimension of the matrix product [(W _d J) ^T (W _d J)]; χ is the attenuation coefficient; λ is the lateral resistivity ρ _h , vertical resistivity ρ _v , The weighting factor of the emitter position parameter (x, y) and the emitter attitude parameter (Azm, Dip) is determined by the following formula

Among them, α and β are weight coefficients, m is the inversion model parameter, (x, y) is the abscissa and ordinate of the emission source, (Azm, Dip) is the azimuth and dip of the emission source.

4. the marine electromagnetic stratum anisotropic resistivity and emitter attitude joint inversion method as claimed in claim 1, is characterized in that, the method for calculating model parameter update amount based on inversion parameter is:

Among them, Δm is the update amount of model parameters in the next iteration, i is the i-th inversion iteration, H _i is the Hessian matrix, and g _i is the gradient of the objective function.

5. seabed anisotropic resistivity as claimed in claim 4 and emitter position joint inversion method, it is characterized in that, the method for seeking the minimum value of objective function is:

Among them, i is the i-th inversion iteration, J _i is the Jacobian matrix.

6. seabed anisotropic resistivity as claimed in claim 1 and emitter position joint inversion method, it is characterized in that, the method for obtaining Jacobian matrix _J is:

Where, i is the i-th inversion iteration; J _i is the Jacobian matrix of the forward modeling response F(m); ρ=(ρ _h , ρ _v ) is the anisotropic resistivity distribution of the formation, P=(x , y) is the location parameter of the transmitter, and T=(Azm, Dip) is the attitude parameter of the transmitter.

7. seabed anisotropic resistivity as claimed in claim 1 and emitter position joint inversion method, it is characterized in that, the method for obtaining Hessian matrix _H is:

Among them, i represents the i-th inversion iteration number.

Compared with the prior art, in some embodiments of the present invention, the beneficial effect of the method provided is:

The present invention mainly aims at the problem of the anisotropy of the seabed medium that widely exists in ocean controllable source detection, and the problem that the position and attitude parameters recorded by the ocean controllable source electromagnetic emission source deviate from the actual position and attitude parameters, resulting in low data quality. A joint inversion method of the anisotropic resistivity of the marine electromagnetic stratum and the location and attitude parameters of the transmitter is proposed. This method considers the anisotropy of the resistivity of the seabed medium and the location and attitude of the transmitter during the inversion process. The influence of parameters on the inversion results can simultaneously invert the anisotropic resistivity of the seabed medium and the location parameters of the electromagnetic emission source, and finally obtain the anisotropic resistivity distribution of the seabed that best fits the actual data. And the accurate position and attitude parameter information of the electromagnetic emission source. This inversion method not only provides an effective inversion method for the interpretation of electromagnetic data with anisotropic electrical resistivity in complex seabed media, but also provides an effective inversion method for data processing problems in the case of errors in the position and attitude parameters of electromagnetic emitters. a feasible technical means. Compared with the traditional inversion algorithm, this method also considers the influence of the anisotropy of the resistivity of the seabed medium and the position and attitude parameters of the transmitter on the inversion results, and combines the two as inversion parameters for simultaneous inversion. This method can effectively Solve the impact of inaccurate emission source position and attitude parameters on the interpretation of ocean controllable source electromagnetic data; the proposed joint inversion method has wider applicability and can be applied to the inversion interpretation of resistivity anisotropy data; fault tolerance It is stronger and can deal with the inversion problem when there is a certain error in the position and attitude parameters of the electromagnetic emission source.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the descriptions of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only of the present invention. For some embodiments, those of ordinary skill in the art can also obtain other drawings based on these drawings without paying creative efforts.

Fig. 1 is a program flow diagram of the inventive method;

Fig. 2 is a structural schematic diagram of a one-dimensional resistivity anisotropy model;

Fig. 3 is a change diagram of the target fitting difference of the inversion iterative model and the number of inversion iterations;

Fig. 4 is the schematic diagram of the inversion result of source position parameter (x, y);

Fig. 5 is a schematic diagram of the inversion result of the emission source attitude parameters (Azm, Dip);

Fig. 6 is a schematic diagram of the inversion of seabed anisotropic resistivity.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The invention provides a joint inversion method of the anisotropic resistivity of the marine electromagnetic stratum and the attitude of the emission source. The inversion parameters are inverted at the same time. This method can effectively solve the problem of low quality of electromagnetic data from marine controllable sources caused by inaccurate emission source position and attitude parameters.

Referring to Fig. 1, a joint inversion method of the anisotropic resistivity of the marine electromagnetic stratum and the attitude of the emitter mainly includes the following steps:

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.

According to the needs of users, the ocean controllable source electromagnetic data files participating in the joint inversion are converted into data files of a specific format, and the input electromagnetic field data are converted into specific parameters (real and imaginary parts of the electromagnetic field, amplitude and phase, Polarization ellipse major axis and minor axis parameters, etc.), complete the reading of inversion data and start the joint inversion.

S2. Set joint inversion execution parameters, the parameters include inversion maximum number of iterations, target fitting difference, maximum iteration step size, step size ratio coefficient, penalty function type, and regularization attenuation coefficient.

The joint inversion process is a complex and huge calculation system, and a large number of parameters need to be used in the process of inversion iteration until the final joint inversion model is obtained. Different inversion execution parameters can obtain different inversion effects, and users can set inversion execution parameters according to the characteristics of the data participating in the joint inversion and the specific needs of the application. The main inversion parameters involved include: maximum number of inversion iterations, target fitting difference, maximum iteration step size, step size ratio coefficient, penalty function type, data components participating in the inversion, regularization attenuation coefficient, etc.

S21. Maximum number of iterations for inversion: the maximum number of iterations for inversion. Setting this parameter can make the joint inversion process exit the joint inversion program after reaching the maximum number of iterations, avoid the continuous loop operation of the inversion program, and improve the calculation efficiency of the program.

S22. Target poor fit: the target value of the degree of fit between the inversion model and the real model. The ultimate goal of joint inversion is to make the inversion model continuously approach the real model, and the poor data fit is the criterion for judging the fit between the inversion model and the real model. The user sets the target fit difference according to the data quality. When the fit difference of the inversion model reaches or is lower than the target fit difference, the joint inversion exits; if the fit difference of the inversion model does not reach the target fit difference, the joint inversion The show will continue.

S23. Maximum iteration step size: the user sets the maximum value of model parameter variation during the joint inversion process. In joint inversion, due to the large order of magnitude span of ocean controllable source electromagnetic field (or other parameters), it is usually taken logarithm before participating in joint inversion operation. If the variation of the iterated model is too large, the result will vary greatly. For example, the variation of the model parameter (after taking the logarithm) is 1.0, that is, the actual value is increased by an order of magnitude. Such a variation value is usually unreasonable. Therefore, this parameter is designed to limit the variation of model parameters.

S24. Step scale coefficient: the user sets the scale coefficient of the model parameter transformation amount in the joint inversion process. The joint inversion involves many inversion parameters. During the inversion iteration process, different inversion parameters change in different degrees. In order to make the overall model change in a reasonable range, the model parameter change can be multiplied by a Ratio coefficient (i.e. step scale coefficient) to ensure the robust convergence of the inversion model.

S25. Penalty function type: a way of restricting model parameters. In the joint inversion process, all model parameters participate in the inversion at the same time, and there is a certain relationship between different inversion parameters. By choosing different penalty functions, the control mode between model parameters can be realized, which can make the model smoother or curved. Effects such as speed increase.

S26. Regularization attenuation coefficient: adaptively select the attenuation coefficient of the regularization factor. In the iterative process of inversion, in order to ensure the ratio relationship between different parameters, the regularization factor needs to be changed accordingly with the number of inversions. This parameter is to set the attenuation coefficient of the regularization factor with the number of iterations.

S3. Setting the initial model parameters of the joint inversion, the parameters include background layer resistivity parameters, thickness parameters, and observation system parameters.

The inversion initial model is the initial value of the parameters of the joint inversion model, and usually needs to be set according to the observation system of the input data and the known water depth data.

S4. Constructing an objective function for joint inversion of anisotropic resistivity and emission source position and attitude parameters.

The joint inversion of ocean controllable source electromagnetic seabed anisotropic resistivity and electromagnetic emission source position and attitude parameters involves multi-attribute inversion parameters, and the relationship between parameters is complex. In view of the different resistivity anisotropy parameters of the seabed medium, and the differences between the location and attitude parameters of the emission source, the present invention uses regularization constraints to stabilize the joint inversion of the electromagnetic seabed anisotropic resistivity and electromagnetic emission source location parameters of the controlled source in the ocean process. The objective function used is:

为模型参数向量的梯度；||·||为标准差算子；d为反演使用的观测数据向量；W_d为数据加权矩阵；W_m为模型加权矩阵；F(m)表示模型m的正演响应算子；μ_ρ、μ_p和μ_T分别为反演模型中海底各向异性电阻率参数m_ρ、发射源位置参数m_P和发射源位置参数m_T的正则化因子。In the formula, φ is the objective function of the inversion algorithm; m is the model inversion parameter vector, which includes the seabed anisotropic resistivity parameter m _ρ , the position parameter m _P of the emission source, and the attitude parameter m _T of the emission source, that is, m =m _ρ +m _P +m _T ;

is the gradient of the model parameter vector; ||·|| is the standard deviation operator; d is the observed data vector used in the inversion; W _d is the data weighting matrix; W _m is the model weighting matrix; Forward modeling response operator; μ _ρ , μ _p and μ _T are the regularization factors of seabed anisotropic resistivity parameter m _ρ , emitter position parameter m _P and emitter position parameter m _T in the inversion model, respectively.

The seafloor resistivity inversion parameter m _ρ of the inversion model has the following form:

In the formula, ρ _h and ρ _v are the lateral resistivity and vertical resistivity of the seabed formation, respectively, and M is the number of layers of the seabed formation.

The emitter position parameter m _p has the following form:

m _P = [l0g ₁₀ x ₁ ... log ₁₀ x _t , log ₁₀ y ₁ ... log ₁₀ y _t ] ^T ;

The attitude inversion parameter m _T of the tilted electric dipole source has the following form:

m _T = [Azm ₁ ... Azm _t , Dip ₁ ... Dip _t ] ^T ;

In the formula, (x, y) is the location parameter of the transmitter (abscissa, ordinate), (Azm, Dip) is the attitude parameter of the transmitter (azimuth, inclination), and t is the number of electric dipole sources.

S5. Calculating the Jacobian matrix and the Hessian matrix of the electromagnetic field with respect to the anisotropic resistivity and the emission source attitude parameters.

S51. The Jacobian matrix J _i is the partial derivative matrix of the electromagnetic field with respect to the inversion parameters, and different inversion parameters have different forms:

Where, i is the i-th inversion iteration; J _i is the Jacobian matrix of the forward modeling response F(m); ρ=(ρ _h , ρ _v ) is the anisotropic resistivity distribution of the formation, P=(x , y) is the location parameter of the transmitter, and T=(Azm, Dip) is the attitude parameter of the transmitter.

If the resistivity tensor ρ is a function of the lateral resistivity ρ _h and vertical resistivity ρ _v of the inversion model, that is, ρ=f(ρ _h , ρ _v ), therefore, the Jacobian of the electromagnetic field with respect to the resistivity tensor ρ The matrix has the following form:

Similarly, the Jacobian matrix of the position inversion parameter m _p and the attitude parameter m _T of the electromagnetic field with respect to the inclined electric dipole source can be obtained as:

In the formula, (x, y) is the location parameter of the transmitter (abscissa, ordinate), (Azm, Dip) is the attitude parameter of the transmitter (azimuth, inclination), and t is the number of electric dipole sources.

S52. The Hessian matrix H _i is the second order derivative of the objective function to the inversion parameters, ignoring the second order derivative term and the asymmetric item, the Hessian matrix H _i can be simplified as:

为模型参数向量的梯度；||·||为标准差算子；d为反演使用的观测数据向量；W_d为数据加权矩阵；W_m为模型加权矩阵；μ_ρ、μ_p和μ_T分别为反演模型中海底各向异性电阻率参数m_ρ、发射源位置参数m_P和发射源位置参数m_T的正则化因子。Among them, i is the i-th inversion iteration, J _i is the Jacobian matrix of the forward modeling response F(m); m _ρ , m _P and m _T are the seafloor resistivity parameters, the position parameters of the transmitter and the attitude parameters ;

is the gradient of the model parameter vector; ||·|| is the standard deviation operator; d is the observed data vector used in the inversion; W _d is the data weighting matrix; W _m is the model weighting matrix; μ _ρ , μ _p and μ _T are the regularization factors of seabed anisotropic resistivity parameter m _ρ , emitter position parameter m _P and emitter position parameter m _T in the inversion model, respectively.

S6. Adaptively calculating a regularization factor based on the characteristics of the inversion parameters.

The selection of the regularization factor μ is the key to solving the joint inversion problem of controlled source electromagnetic seabed anisotropic resistivity and electromagnetic emission source parameters whether it is reasonable or not. In geophysical inversion methods, many regularization factor selection methods have emerged. When carrying out joint inversion of ocean controllable source electromagnetic seabed anisotropic resistivity and electromagnetic emission source parameters, the present invention selects different regularization factors for different inversion parameters. First, select the characteristic parameters of the Jacobian matrix in the inversion process as the base, and then adjust the regularization factors of different inversion parameters in combination with the characteristics of the inversion parameters and the relationship between parameters, so as to realize the regularization factor adaptive selection.

The regularization factor μ _i can be written as follows:

_In the formula, i represents the i-th inversion iteration; _{μ i} is the regularization factor; Max|·| is _the element with the largest absolute value of ^the matrix; ]; M is _the dimension of the matrix product [(W _d J) ^T (W _{d J} )]; χ is the attenuation coefficient; The weighting factors of parameters (x, y) and emitter attitude parameters (Azm, Dip) are determined by the following formula:

Among them, α and β are weight coefficients, m is an inversion model parameter, and the initial value λ ₁ of the weight vector is a unit vector. When there is resistivity anisotropy in the inversion model formation, the regularization factor can be adjusted adaptively according to the resistivity anisotropy rate, thereby adjusting the weights among the elements in the objective function, so as to achieve adaptive adjustment of the inversion effect of the process.

S7. Calculate the model update amount.

The model update amount can be calculated by finding the minimum value of the objective function, that is, the objective function gradient g _i =0, which can be determined by the following formula

为模型参数向量的梯度；||·||为标准差算子；d为反演使用的观测数据向量；W_d为数据加权矩阵；W_m为模型加权矩阵；F(m)表示模型m的正演响应算子；μ_ρ、μ_p和μ_T分别为反演模型中海底各向异性电阻率参数m_ρ、发射源位置参数m_P和发射源位置参数m_T的正则化因子。Among them, i is the i-th inversion iteration, J _i is the Jacobian matrix of the forward modeling response F(m); φ is the objective function of the inversion algorithm; m _ρ , m _P and m _T are the seafloor resistivity parameters , the location parameters and attitude parameters of the emission source;

is the gradient of the model parameter vector; ||·|| is the standard deviation operator; d is the observed data vector used in the inversion; W _d is the data weighting matrix; W _m is the model weighting matrix; Forward modeling response operator; μ _ρ , μ _p and μ _T are the regularization factors of seabed anisotropic resistivity parameter m _ρ , emitter position parameter m _P and emitter position parameter m _T in the inversion model, respectively.

The calculated model parameter update amount for the next iteration is Δm, which can be expressed as:

Among them, Δm is the update amount of model parameters in the next iteration, i is the i-th inversion iteration, H _i is the Hessian matrix, and g _i is the gradient of the objective function.

S8. Calculate the fitting difference of the objective function of the inversion iterative model.

During the inversion iteration process, the inversion iteration model gradually converges to the real model, and its objective function fitting difference ψ gradually converges to 1.0. The objective function fitting difference ψ has the following form:

Among them, i is the number of inversion iterations, d is the observation data vector used in inversion; F(m) represents the forward response operator of model m; N is the number of inversion data; k is the serial number of inversion data; δ _k is the standard deviation of the kth data.

S9. Judging whether the inversion requirement is satisfied, if so, turn to S9, and if not, turn to S5.

There are two criteria for judging whether to quit the joint inversion: 1) whether the poor fit of the joint inversion target is met; 2) whether the number of inversion iterations reaches the maximum number of iterations. If not, turn to S5, and continue to iteratively solve the model update amount; if yes, turn to S10.

S10. Outputting the final inversion model.

Referring to Figure 2, it is a schematic diagram of a one-dimensional typical geoelectric model. In order to verify the validity of the combined inversion of ocean controlled source electromagnetic seabed anisotropic resistivity and electromagnetic emission source parameters, taking the one-dimensional resistivity anisotropy model shown in Fig. Joint inversion of rate and emitter parameters. It is assumed that 26 electromagnetic emission sources are arranged at equal intervals within the range of 500m-13000m of the survey line, and are all located 50m directly above the seabed. The attitude of each emission source is the same and the azimuth angle is 90 degrees, and the inclination angle is 5 degrees; The receiving station is arranged at (0, 0, 1000) on the seabed. Set the emission current to 1 amp. The inversion data consist of the real and imaginary parts of each component of the electromagnetic field, and 2% random Gaussian noise is added to each data. In the inversion calculation example, the initial inversion model is air, seawater and a uniform half space with a resistivity of 1Ωm, and the resistivity and depth of the air layer and seawater are fixed. Set the position of the survey line of the electromagnetic emission source in the inversion initial model to intersect with the position of the real survey line (there is an angle of about 45°).

Referring to Fig. 3, it is a schematic diagram of the relationship between the target fitting difference of the inversion iteration model and the number of inversion iterations. It can be seen from the figure that during the joint inversion process, the fitting difference of the objective function continues to decrease and gradually approaches the real model, and from the initial large fitting difference of 17, after 20 inversion iterations, it finally converges to 3.1.

Referring to Fig. 4, it is the inversion result of the emission source position parameters. It can be seen from Fig. 4 that the ordinate and abscissa in the figure are the position of (x, y) respectively, the hollow triangle is the initial position of the electromagnetic emission source, the solid triangle is the real position of the electromagnetic emission source, and the solid circle is the joint inversion obtained The position of the electromagnetic emission source, even if the input position of the emission source is quite different from the real position (the position difference is as high as 100m), the joint inversion can still obtain relatively accurate position information (the distance between the electromagnetic emission source position obtained by the inversion and the real position is not the same. more than 25m), which shows that the emitter position obtained by the joint inversion is accurate.

Referring to Fig. 5, it is the inversion result of the emission source attitude parameters. The abscissa is the y-coordinate of the emission source, the left ordinate is the azimuth of the electromagnetic emission source, and the right ordinate is the inclination angle of the electromagnetic emission source. The squares and hexagonal hollow lines are the initial values of the azimuth and inclination of the emission source respectively. The squares and The hexagonal solid line is the azimuth and inclination angle of the electromagnetic emission source obtained by the joint inversion. It can be seen that the deviation of the azimuth and inclination angle of the emission source from the joint inversion and the true value is not more than 5 degrees and 1 degree respectively, which shows that the inversion obtained The attitude parameters (azimuth and inclination) of the electromagnetic emission source are all accurate;

Referring to Figure 6, it is the inversion result map of the anisotropic resistivity of the seabed. The light gray and dark gray line segments represent the real lateral and vertical resistivity distribution of the seabed medium, and the light gray and dark gray stepped curves represent the seabed obtained from the inversion. The lateral resistivity and vertical resistivity curves of the medium can be seen from the figure. The anisotropic resistivity of the surrounding rocks jointly inverted is consistent with the real situation, and the buried depth, thickness and vertical resistivity of the high-resistivity layer have also been compared. accurate recovery. To sum up, the combined inversion method of ocean controllable source electromagnetic seabed anisotropic resistivity and electromagnetic emission source parameters proposed by the present invention can invert the anisotropic resistivity information of the seabed medium and the position state parameters of the electromagnetic emission source . This also shows that the algorithm proposed by the present invention is effective.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (6)

1. A joint inversion method for the anisotropic resistivity of the marine electromagnetic formation and the attitude of the transmitter, characterized in that it comprises: 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 polarization ellipse major axis and minor axis parameters; S2. Setting joint inversion execution parameters, said parameters including inversion maximum number of iterations, target fitting difference, maximum iteration step size, step size ratio coefficient, penalty function type, and regularization attenuation coefficient; S3. Establish the observation system and design the initial joint inversion model; S4. Construct the joint inversion objective function of anisotropic resistivity and emission source attitude parameters; specifically: use regularization constraints to stabilize the ocean controllable source electromagnetic seabed anisotropic resistivity and electromagnetic emission source position parameters joint inversion process; S5. Calculating the Jacobian matrix and the Hessian matrix of the electromagnetic field about the anisotropic resistivity and the attitude parameters of the emission source; S6. Adaptively calculate the regularization factor based on the characteristics of the inversion parameters; S7. Calculating the update amount of the anisotropic resistivity and the attitude parameter of the emission source; S8. Calculate the fitting difference of the objective function of the inversion iterative model; S9. Judging whether the inversion requirements are met, if so, turn to S10, and if not, turn to S5; S10, outputting the final inversion model; The objective function of constructing the joint inversion of anisotropic resistivity and emission source attitude parameters is:

In the formula, φ is the objective function of the inversion algorithm; m is the model inversion parameter vector, which includes the seabed anisotropic resistivity parameter m _ρ , the position parameter m _P of the emission source, and the attitude parameter m _T of the emission source, that is, m ＝m _ρ +m _P +m _T ; is the gradient of the model parameter vector; ||·|| is the standard deviation operator; d is the observed data vector used in inversion; W _d is the data weighting matrix; W _m is the model weighting matrix; F(m) represents the forward response operator of model m; μ _ρ , μ _p and μ _T are the seabed anisotropic resistivity parameter m _ρ , emitter position parameter m _P and emitter position in the inversion model, respectively Regularization factor for parameter _mT . 2. the joint inversion method of anisotropic resistivity of marine electromagnetic stratum as claimed in claim 1 and emitter attitude, is characterized in that, described self-adaptive regularization factor is determined according to the following formula:

_In the formula, i represents the i-th _inversion iteration; μ _i is the regularization factor _; Max|·| is the element with the largest absolute value of the matrix; ]; M is the dimension of the matrix product [(W _d J)T(W _d J)]; χ is the attenuation coefficient; λ is the lateral resistivity ρ _h , vertical resistivity ρ _v , The weighting factor of the emitter position parameter (x, y) and the emitter attitude parameter (Azm, Dip) is determined by the following formula

Among them, α and β are weight coefficients, m is the inversion model parameter, (x, y) is the abscissa and ordinate of the emission source, (Azm, Dip) is the azimuth and dip of the emission source. 3. the marine electromagnetic stratum anisotropic resistivity and emitter attitude joint inversion method as claimed in claim 1, is characterized in that, the method for calculating model parameter update amount based on inversion parameter is:

Among them, Δm is the update amount of model parameters in the next iteration, i is the i-th inversion iteration, H _i is the Hessian matrix, and g _i is the gradient of the objective function. 4. marine electromagnetic stratum anisotropic resistivity and emitter attitude joint inversion method as claimed in claim 3, is characterized in that, the method for seeking the minimum value of objective function is:

Among them, i is the i-th inversion iteration, J _i is the Jacobian matrix. 5. the joint inversion method of the anisotropic resistivity of marine electromagnetic stratum as claimed in claim 1 and emission source attitude is characterized in that, the method for obtaining Jacobian matrix _J is:

Where, i is the i-th inversion iteration; J _i is the Jacobian matrix of the forward modeling response F(m); ρ=(ρ _h , ρ _v ) is the anisotropic resistivity distribution of the formation, P=(x , y) is the location parameter of the transmitter, and T=(Azm, Dip) is the attitude parameter of the transmitter. 6. the joint inversion method of the anisotropic resistivity of marine electromagnetic stratum as claimed in claim 1 and emission source attitude is characterized in that, the method for obtaining Hessian matrix Hi is:

Among them, i represents the i-th inversion iteration number.

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