阅读说明：本技术 一种深海地震垂直缆二次定位方法 (Secondary positioning method for deep-sea seismic vertical cable ) 是由 尉佳 陆凯 冯京 王威 于得水 单瑞 李阳 秦珂 董凌宇 苏肖亮 翟元峰 马理 于 2021-08-05 设计创作，主要内容包括：本发明公开了一种深海地震垂直缆二次定位方法,包括如下步骤：步骤1,采集原始地震信号；步骤2,激发点定位；步骤3,初至时间自动拾取；步骤4,建立基于等效速度的初至走时方程,基于初至走时方程建立函数,并利用牛顿迭代方法进行全局最优计算,求解得到垂直缆每个检波点的坐标,并利用道间距判断坐标误差；步骤5,选择不同时间段的激发点,按照步骤2至步骤4的方法定时进行垂直缆的二次定位,从而计算出垂直缆的位置变化。本发明所公开的方法能够提高地震数据处理以及解释的精度,为最终地质成果提供位置信息支撑。(The invention discloses a secondary positioning method for a deep-sea seismic vertical cable, which comprises the following steps: step 1, collecting original seismic signals; step 2, positioning an excitation point; step 3, automatically picking up the first arrival time; step 4, establishing a first-arrival travel time equation based on equivalent speed, establishing a function based on the first-arrival travel time equation, performing global optimal calculation by using a Newton iteration method, solving to obtain the coordinate of each demodulator probe of the vertical cable, and judging a coordinate error by using a track interval; and 5, selecting excitation points in different time periods, and carrying out secondary positioning on the vertical cable at regular time according to the method from the step 2 to the step 4, thereby calculating the position change of the vertical cable. The method disclosed by the invention can improve the precision of seismic data processing and interpretation and provide position information support for the final geological result.)

1. A secondary positioning method for a deep-sea seismic vertical cable is characterized by comprising the following steps:

step 1, collecting original seismic signals: after the vertical cable is launched to the sea bottom, a ship-mounted air gun seismic source in navigation is adopted to continuously excite signals on the sea surface, a wave detection point on the vertical cable receives signals sent by an excitation point and reflection signals of the sea bottom, and after operation is finished, data received by the vertical cable are recovered and are original seismic signals of secondary positioning of the vertical cable;

step 2, excitation point positioning: calculating the coordinate of each excitation point by using shipborne navigation software, a shipborne attitude instrument and a shipborne GPS antenna;

step 3, automatically picking up the first arrival time: performing wavelet transformation on the original seismic signals, calculating an instantaneous phase spectrum of the transformed wavelet domain signals, and obtaining the time of the first time of the sound waves from an excitation point to a detection point, namely the first arrival time according to the instantaneous phase spectrum;

step 4, taking the coordinate of each wave detection point of the vertical cable and the equivalent sound wave velocity as variables, taking the coordinate of each excitation point as a known quantity, establishing a first arrival travel time equation, establishing a function based on the first arrival travel time equation, performing global optimal calculation by using a Newton iteration method, and solving to obtain the coordinate of each wave detection point of the vertical cable;

in order to verify the correctness of the secondary positioning value, the distance between two adjacent detection points obtained by calculation and the actual track spacing are required to be subjected to constraint calculation, if the error is smaller than a preset threshold value, the secondary positioning result is considered to be correct, and if the error is larger than the preset threshold value, the first-arrival travel time course global optimum calculation is carried out again until the error is smaller than the preset threshold value;

and 5, selecting excitation points in different time periods, and carrying out secondary positioning on the vertical cable at regular time according to the method from the step 2 to the step 4, thereby calculating the position change of the vertical cable.

2. The deep-sea seismic vertical cable secondary positioning method according to claim 1, wherein in the step 2, the air gun seismic source is towed behind the ship through a soft air pipe connection, and the coordinates of the excitation point of the air gun seismic source are calculated by using a space geometric relationship in combination with the position information of the ship-mounted GPS antenna, the ship attitude information measured by the ship-mounted attitude instrument and the distance from the excitation point of the air gun seismic source to the stern.

3. The deep sea seismic vertical cable secondary positioning method according to claim 1, wherein the specific method of step 3 is as follows:

(1) transforming the original seismic signals by using a wavelet transformation method:

let f be the original seismic signal of the i-th excitation point received by the corresponding j-th detection point in the original seismic signal f (t)_ij(t) wavelet function is Ψ_a，b(t), the original seismic signals f (t) are obtained after wavelet transformation:

wherein t is time, a is a time scale parameter, b is a translation parameter,is Ψ_a，b(t) conjugate function, U_ij(a, b) is f_ij(t) corresponding wavelet domainA signal;

(2) calculating an instantaneous phase spectrum:

due to f_ij(t) includes noise interference, so that the threshold s is set when analyzing the signal_0ijWhen the following formula is satisfied:

|U_ij(a，b_max)|≤s_0ij*mean(|U_ij(a，b)|) (2)

calculating f when the time scale is a and the translation parameter b takes the maximum value_ij(t) instantaneous phase spectrum, the calculation formula is as follows:

wherein, U_ij(a，b_max) Representing the time scale as a, when the translation parameter b takes the maximum value, f_ij(t) corresponding wavelet domain signal, mean (| U)_ij(a，b_max) | U) represents | U_ij(a，b_max) Average of |, Iang_ij(a) Representing the time scale as a, when the translation parameter b takes the maximum value, f_ij(t) instantaneous phase spectrum, imag (U)_ij(a，b_max) Is U)_ij(a，b_max) Imaginary part of (U)_ij(a，b_max) Is U)_ij(a，b_max) The real part of (a);

(3) calculating the first arrival time:

calculated instantaneous phase spectrum Iang_ij(a) The first zero point position from negative to positive, and the corresponding time is f_ij(t) first arrival time t_ij。

4. The deep sea seismic vertical cable secondary positioning method according to claim 1, wherein the specific method of step 4 is as follows:

(1) the first arrival travel time process is established as follows:

(x_j-x_i)²+(y_j-y_i)²+(z_j-z_i)²＝(v_jt_ij)² (4)

wherein (x)_j，y_j，z_j) Is the coordinate of the jth detection point, (x)_i，y_i，z_i) Is the coordinate of the i-th excitation point, v_jRepresents an equivalent velocity at the j-th detection point, t_ijRepresenting the first arrival time of the sound wave emitted by the ith excitation point to the jth detection point;

(2) the solution of the above equation is converted into a zero problem of the function:

defining a function phi_ij(x，y，z，v，t)＝(x_j-x_i)²+(y_j-y_i)²+(z_j-z_i)²-(v_jt_ij)² (5)

The formula (5) is set at the initial point (x) of the detection point_j0，y_j0，z_j0，v_j0) The process taylor expansion is obtained by the process taylor expansion,

JP＝Φ_ij(x_j0，y_j0，z_j0，v_j0) (6)

wherein the Jacobian matrix J is phi_ij(x, y, z, v, t) at point (x)_j0，y_j0，z_j0，v_j0) At the first derivative of each variable, P is the offset of the solution, (x)_j0，y_j0，z_j0) Initial coordinates, v, representing the jth detection point_j0Representing the initial equivalent speed of the j detection point instead of the sound velocity, and taking 1500 m/s;

(3) solving an overdetermined linear equation (6) by using a Newton iteration method to obtain the coordinate (x ') of the j-th detection point'_j，y′_j，z′_j) If the distance between two adjacent detection points satisfies d obtained by calculation_j，j+1D is the vertical cable channel spacing, namely the actual spacing between two adjacent detection points, namely the error is within the range of a set threshold value, and the coordinate of each detection point on the vertical cable can be obtained.

Technical Field

The invention relates to the technical field of submarine exploration, in particular to a secondary positioning method for a deep-sea seismic vertical cable.

Background

As an important part of the marine stereo observation system, research related to the marine vertical cable seismic exploration technology is increasingly important. Compared with the traditional horizontal streamer or ocean bottom seismograph, the vertical cable receiving signal is not influenced by factors such as sea surface environment noise, ocean bottom pipeline arrangement conditions and the like. Due to the particularity of the observation system, the longitudinal distribution of the detectors can meet the requirement of high transverse resolution, and the up-and-down traveling waves are easy to separate. The vertical cable acquisition technology can obtain richer seismic wave field information, and realize true three-dimensional, wide reflection angle, omnidirectional angle and high-precision imaging on a specific geological target. The technology has the advantages of flexible design of an observation system, improvement of imaging precision of a specific target body, improvement of four-dimensional seismic monitoring effect and the like.

Similar to the conventional OBS and OBN, the deviation exists between the actual position of the vertical cable at the bottom and the designed point position, the seabed arrangement position of the vertical cable can change along with the time, and the vertical cable needs to be secondarily positioned in order to ensure the accuracy of data acquisition post-processing and interpretation. At the present stage, a plurality of methods for secondary positioning of an ocean bottom seismograph and the like exist, but a secondary positioning method for a deep sea seismic vertical cable with higher precision and more wave detection points does not exist.

Disclosure of Invention

In order to solve the technical problems, the invention provides a secondary positioning method for a deep-sea seismic vertical cable, so as to achieve the purposes of improving the precision of seismic data processing and interpretation and providing support for final geological results.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a secondary positioning method for a deep-sea seismic vertical cable comprises the following steps:

step 1, collecting original seismic signals: after the vertical cable is launched to the sea bottom, a ship-mounted air gun seismic source in navigation is adopted to continuously excite signals on the sea surface, a wave detection point on the vertical cable receives signals sent by an excitation point and reflection signals of the sea bottom, and after operation is finished, data received by the vertical cable are recovered and are original seismic signals of secondary positioning of the vertical cable;

step 2, excitation point positioning: calculating the coordinate of each excitation point by using shipborne navigation software, a shipborne attitude instrument and a shipborne GPS antenna;

step 3, automatically picking up the first arrival time: performing wavelet transformation on the original seismic signals, calculating an instantaneous phase spectrum of the transformed wavelet domain signals, and obtaining the time of the first time of the sound waves from an excitation point to a detection point, namely the first arrival time according to the instantaneous phase spectrum;

step 4, taking the coordinate of each wave detection point of the vertical cable and the equivalent sound wave velocity as variables, taking the coordinate of each excitation point as a known quantity, establishing a first arrival travel time equation, establishing a function based on the first arrival travel time equation, performing global optimal calculation by using a Newton iteration method, and solving to obtain the coordinate of each wave detection point of the vertical cable;

in order to verify the correctness of the secondary positioning value, the distance between two adjacent detection points obtained by calculation and the actual track spacing are required to be subjected to constraint calculation, if the error is smaller than a preset threshold value, the secondary positioning result is considered to be correct, and if the error is larger than the preset threshold value, the first-arrival travel time course global optimum calculation is carried out again until the error is smaller than the preset threshold value;

and 5, selecting excitation points in different time periods, and carrying out secondary positioning on the vertical cable at regular time according to the method from the step 2 to the step 4, thereby calculating the position change of the vertical cable.

In the scheme, in the step 2, the air gun seismic source is connected and towed behind the ship through a soft air pipe, and the coordinates of the excitation point of the air gun seismic source are calculated by utilizing the space geometric relationship by combining the position information of the ship-borne GPS antenna, the ship body attitude information measured by the ship-borne attitude instrument and the distance from the excitation point of the air gun seismic source to the stern.

In the above scheme, the specific method of step 3 is as follows:

(1) transforming the original seismic signals by using a wavelet transformation method:

let f be the original seismic signal of the i-th excitation point received by the corresponding j-th detection point in the original seismic signal f (t)_ij(t) wavelet function is Ψ_a，b(t), the original seismic signals f (t) are obtained after wavelet transformation:

wherein t is time, a is a time scale parameter, b is a translation parameter,is Ψ_a，b(t) conjugate function, U_ij(a, b) is f_ij(t) corresponding wavelet domain signals;

(2) calculating an instantaneous phase spectrum:

due to f_ij(t) includes noise interference, soSetting a threshold s during the analysis of the signal_0ijWhen the following formula is satisfied:

|U_ij(a，b_max)|≤s_0ij*mean(|U_ij(a，b)|) (2)

calculating f when the time scale is a and the translation parameter b takes the maximum value_ij(t) instantaneous phase spectrum, the calculation formula is as follows:

wherein, U_ij(a，b_max) Representing the time scale as a, when the translation parameter b takes the maximum value, f_ij(t) corresponding wavelet domain signal, mean (| U)_ij(a，b_max) | U) represents | U_ij(a，b_max) Average of |, Iang_ij(a) Representing the time scale as a, when the translation parameter b takes the maximum value, f_ij(t) instantaneous phase spectrum, imag (U)_ij(a，b_max) Is U)_ij(a，b_max) Imaginary part of (U)_ij(a，b_max) Is U)_ij(a，b_max) The real part of (a);

(3) calculating the first arrival time:

calculated instantaneous phase spectrum Iang_ij(a) The first zero point position from negative to positive, and the corresponding time is f_ij(t) first arrival time t_ij。

In the above scheme, the specific method of step 4 is as follows:

(1) the first arrival travel time process is established as follows:

(x_j-x_i)²+(y_j-y_i)²+(z_j-z_i)²＝(v_jt_ij)2 (4)

wherein (x)_j，y_j，z_j) Is the coordinate of the jth detection point, (x)_i，y_i，z_i) Is the coordinate of the i-th excitation point, v_jRepresents an equivalent velocity at the j-th detection point, t_ijIndicating emission of ith excitation pointThe first arrival time of the sound wave reaching the jth detection point;

(2) the solution of the above equation is converted into a zero problem of the function:

defining a function phi_ij(x，y，z，v，t)＝(x_j-x_i)²+(y_j-y_i)²+(z_j-z_i)²-(v_jt_ij)² (5)

The formula (5) is set at the initial point (x) of the detection point_j0，y_j0，z_j0，v_j0) The process taylor expansion is obtained by the process taylor expansion,

JP＝Φ_ij(x_j0，y_j0，z_j0，v_j0) (6)

wherein the Jacobian matrix J is phi_ij(x, y, z, v, t) at point (x)_j0，y_j0，z_j0，v_j0) At the first derivative of each variable, P is the offset of the solution, (x)_j0，y_j0，z_j0) Initial coordinates, v, representing the jth detection point_j0Representing the initial equivalent speed of the j detection point instead of the sound velocity, and taking 1500 m/s;

(3) solving an overdetermined linear equation (6) by using a Newton iteration method to obtain the coordinate (x ') of the j-th detection point'_j，y′_j，z′_j) If the distance between two adjacent detection points satisfies d obtained by calculation_j，j+1D is the vertical cable channel spacing, namely the actual spacing between two adjacent detection points, namely the error is within the range of a set threshold value, and the coordinate of each detection point on the vertical cable can be obtained.

Through the technical scheme, the deep-sea seismic vertical cable secondary positioning method provided by the invention combines data such as the position of a seismic source excitation point, primary positioning information and the like through original seismic signal analysis, establishes a first arrival travel time equation through picking up first arrival time, reversely shows the actual position of each detection point of the deep-sea seismic vertical cable, can obtain position change data of the vertical cable along with time, and provides support for subsequent deep-sea seismic vertical cable data processing.

The method has accurate data processing, accurate obtained position information and provides accurate position information for data analysis of the deep sea bottom layer.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.

FIG. 1 is a schematic diagram of a deep sea seismic vertical cable acquisition technique according to an embodiment of the present invention;

fig. 2 is a flowchart of a secondary positioning method of the present invention.

In the figure, 1, a ship; 2. an air gun seismic source; 3. a vertical cable; 4. a balancing weight; 5. a floating ball; 6. an excitation point; 7. and (5) a wave detection point.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

The invention provides a secondary positioning method for a deep-sea seismic vertical cable, which comprises the following steps:

step 1, collecting original seismic signals:

before the operation, adjust to operating condition with perpendicular cable 3 after, put in the seabed with perpendicular cable 3, perpendicular cable 3 bottom sets up balancing weight 4, and 3 top connection floater 5 of perpendicular cable. Continuously exciting seismic wave signals at an excitation point 6 in a certain range on the sea surface by adopting a carrier gas gun seismic source 2 of a sailing ship 1 according to a construction design mode, receiving the seismic wave signals sent out at the excitation point 6 and reflected wave signals at the sea bottom by a wave detection point 7 on a vertical cable 3, and recovering data received by the vertical cable after operation is finished, wherein the data are original seismic signals for secondary positioning of the vertical cable;

step 2, excitation point positioning:

the ship-borne navigation software can receive the GPS position information of the ship body in real time, and the GPS antenna is fixed in position and can accurately measure. The ship body is influenced by ocean current and wind direction, three attitude changes are generated on the sea surface, and the ship-borne attitude instrument can record three attitude change information of the ship body in real time. The air gun seismic source is connected and towed behind the ship through a soft air pipe and the like, and the distance between the excitation point of the air gun seismic source and the stern can be measured.

And by integrating the GPS antenna position, the three attitude information of the ship body and the distance from the excitation point of the air gun seismic source to the stern, and by utilizing the space geometric relationship, the accurate coordinate of the excitation point of the air gun seismic source can be calculated.

Step 3, automatically picking up the first arrival time:

performing wavelet transformation on the original seismic signals, calculating an instantaneous phase spectrum of the transformed wavelet domain signals, and obtaining the time of the first time of the sound waves from an excitation point to a detection point, namely the first arrival time according to the instantaneous phase spectrum;

the specific method comprises the following steps:

(1) transforming the original seismic signals by using a wavelet transformation method:

let f be the original seismic signal of the i-th excitation point received by the corresponding j-th detection point in the original seismic signal f (t)_ij(t) wavelet function is Ψ_a，b(t), the original seismic signals f (t) are obtained after wavelet transformation:

wherein t is time, a is a time scale parameter, b is a translation parameter,is Ψ_a，b(t) conjugate function, U_ij(a, b) is f_ij(t) corresponding wavelet domain signals;

(2) calculating an instantaneous phase spectrum:

due to f_ij(t) includes noise interference, so that the threshold s is set when analyzing the signal_0ijWhen the following formula is satisfied:

|U_ij(a，b_max)|≤s_0ij*mean(|U_ij(a，b)|) (2)

calculating f when the time scale is a and the translation parameter b takes the maximum value_ij(t) instantaneous phase spectrum, the calculation formula is as follows:

wherein, U_ij(a，b_max) Representing the time scale as a, when the translation parameter b takes the maximum value, f_ij(t) corresponding wavelet domain signal, mean (| U)_ij(a，b_max) | U) represents | U_ij(a，b_max) Average of |, Iang_ij(a) Representing the time scale as a, when the translation parameter b takes the maximum value, f_ij(t) instantaneous phase spectrum, imag (U)_ij(a，b_max) Is U)_ij(a，b_max) Imaginary part of (U)_ij(a，b_max) Is U)_ij(a，b_max) The real part of (a);

(3) calculating the first arrival time:

calculated instantaneous phase spectrum Iang_ij(a) The first zero point position from negative to positive, and the corresponding time is f_ij(t) first arrival time t_ij。

Step 4, taking the coordinate of each wave detection point of the vertical cable and the equivalent sound wave velocity as variables, taking the coordinate of each excitation point as a known quantity, establishing a first arrival travel time equation, establishing a function based on the first arrival travel time equation, performing global optimal calculation by using a Newton iteration method, and solving to obtain the coordinate of each wave detection point of the vertical cable;

in order to verify the correctness of the secondary positioning value, the distance between two adjacent detection points obtained by calculation and the actual track spacing are required to be subjected to constraint calculation, if the error is smaller than a preset threshold value, the secondary positioning result is considered to be correct, and if the error is larger than the preset threshold value, the first-arrival travel time course global optimum calculation is carried out again until the error is smaller than the preset threshold value;

the specific method comprises the following steps:

(1) the first arrival travel time process is established as follows:

(x_j-x_i)²+(y_j-y_i)²+(z_j-z_i)²＝(v_jt_ij)² (4)

wherein (x)_j，y_j，z_j) Is the coordinate of the jth detection point, (x)_i，y_i，z_i) Is the coordinate of the i-th excitation point, v_jRepresents an equivalent velocity at the j-th detection point, t_ijRepresenting the first arrival time of the sound wave emitted by the ith excitation point to the jth detection point;

(2) the solution of the above equation is converted into a zero problem of the function:

defining a function phi_ij(x，y，z，v，t)＝(x_j-x_i)²+(y_j-y_i)²+(z_j-z_i)²-(v_jt_ij)² (5)

The formula (5) is set at the initial point (x) of the detection point_j0，y_j0，z_j0，v_j0) The process taylor expansion is obtained by the process taylor expansion,

JP＝Φ_ij(x_j0，y_j0，z_j0，v_j0) (6)

wherein the Jacobian matrix J is phi_ij(x, y, z, v, t) at point (x)_j0，y_j0，z_j0，v_j0) At the first derivative of each variable, P is the offset of the solution, (x)_j0，y_j0，z_j0) Initial coordinates, v, representing the jth detection point_j0Representing the initial equivalent speed of the j detection point instead of the sound velocity, and taking 1500 m/s; the initial point of the geophone point refers to the initial position of the vertical cable after it has been submerged in the sea floor.

(3) Solving an overdetermined linear equation (6) by using a Newton iteration method to obtain the coordinate (x ') of the j-th detection point'_j，y′_j，z′_j) If the distance between two adjacent detection points satisfies d obtained by calculation_j，j+1D is the vertical cable channel spacing, namely the actual spacing between two adjacent detection points, the error range is 0 & lt delta & lt o (delta), the o (delta) is a set threshold, namely the error is in the range of the set threshold, and the coordinate of each detection point on the vertical cable can be obtained.

And 5, the vertical cable is influenced by ocean currents on the seabed, and the posture and the position of the vertical cable are changed. And (4) in order to ensure that the attitude of the vertical cable is determined at regular time, selecting a corresponding seismic source excitation point by taking the date as a reference, and carrying out secondary positioning on the vertical cable at regular time according to the method from the step 2 to the step 4 so as to calculate the position change of the vertical cable.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.