A method and system for measuring the relative motion speed of an air gun seismic source bubble

Abstract

The present invention provides a method and system for measuring the relative motion speed of an air gun seismic source bubble, belonging to the field of marine seismic exploration. The method for measuring the relative motion speed of the air gun seismic source bubble obtains the motion speed of the bubble relative to the hydrophone according to the course and speed of the seismic source ship and the measured floating time of bubbles of air guns with different capacities. By using the present invention, the relative motion speed of the bubble excited by the air gun seismic source can be obtained; through actual tests, it shows that the relative motion speed of the air gun seismic source bubble measured by the present invention can be used for far-field wavelet simulation, and improves the accuracy and reliability of far-field wavelet simulation.

Description

Technical Field

[0001] The present invention belongs to the field of marine seismic exploration, and particularly relates to a method and system for measuring the relative movement speed of an air gun source bubble. Background Art

[0002] The air gun source is the main source form for marine seismic exploration. The quality of the air gun source directly affects the quality of marine seismic exploration data. The far-field wavelet after the air gun source is excited is an important parameter for subsequent seismic processing and data quality monitoring.

[0003] Marine air gun sources are generally excited in the form of an air gun array combination. Simulating the far-field wavelet through near-field recording is one of the common simulation methods. The near-field recording is obtained by hydrophones arranged above each air gun. In the current methods for simulating the far-field wavelet by near-field recording, it is generally considered that the positions of the hydrophone and the bubble excited by the air gun are unchanged, that is, the relative distance between them is fixed. However, the fact is that the oscillating bubble generated after the air gun is excited will float upward. At the same time, during the ship's movement, the distance between the center position of the bubble and the hydrophone caused by the movement of the hydrophone recording the near field with the ship changes over time. This change will inevitably affect the accuracy of the far-field wavelet simulation. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art, and provide a method and system for measuring the relative movement speed of an air gun source bubble, so as to improve the accuracy of simulating the far-field wavelet by near-field recording by measuring the movement speed of the bubble relative to the hydrophone.

[0005] The present invention is realized by the following technical solutions:

[0006] In the first aspect of the present invention, a method for measuring the relative movement speed of an air gun source bubble is provided. The method obtains the movement speed of the bubble relative to the hydrophone according to the heading and speed of the source ship, and the measured floating time of the bubbles of different capacities of the air gun.

[0007] The further improvement of the present invention lies in:

[0008] The method includes:

[0009] (1) Obtain the heading and speed of the source ship;

[0010] (2) Measure the floating time of the bubble;

[0011] (3) Calculate the floating speed of the bubble;

[0012] (4) Obtain the movement speed of the bubble relative to the hydrophone.

[0013] The further improvement of the present invention lies in:

[0014] The operations in step (1) include:

[0015] (11) Obtain the course φ of the seismic source vessel from the navigation system of the seismic source vessel nav and the speed v nav ;

[0016] (12) Calculate and obtain the horizontal motion speed component of the hydrophone using the following formula:

[0017] v x = v nav cosφ

[0018] v y = v nav sinφ

[0019] where v x and v y are the speed components in the x-axis and y-axis directions respectively.

[0020] A further improvement of the present invention lies in:

[0021] The operations in step (2) include:

[0022] (21) Record the generation time t 1,i of the bubbles below the sea surface when a single gun is fired, and the disappearance time t 2,i of the bubbles after they float to the sea surface, and calculate and obtain the floating time t i of the bubbles using the following formula: t i = t 2,i - t 1,i where i represents the serial number of the air gun;

[0023] (22) Repeat step (21) for air guns of all capacities to obtain the floating times of the bubbles of each capacity of air gun.

[0024] A further improvement of the present invention lies in:

[0025] The operations in step (22) further include:

[0026] Repeat the operations in step (21) multiple times for air guns of the same capacity to obtain multiple floating times of the bubbles, and take the average value of the obtained multiple floating times of the bubbles as the floating time of the bubbles of this air gun.

[0027] A further improvement of the present invention lies in:

[0028] The operations in step (3) include

[0029] (31) Obtain the sinking depth h i ;

[0030] (32) The bubble rising velocity v of the air gun is calculated using the following formula z,i : v z,i = h i / t i ;

[0031] (33) Repeat steps (31) and (32) to obtain the bubble rising velocities of air guns with all capacities;

[0032] (34) Plot a scatter diagram of capacity vs. velocity;

[0033] (35) Perform logarithmic fitting on the scatter diagram of capacity vs. velocity to obtain a fitting expression for capacity vs. velocity.

[0034] A further improvement of the present invention lies in:

[0035] The operation of step (34) includes:

[0036] Plot the bubble rising velocities of air guns with all capacities in a coordinate diagram with capacity as the abscissa and rising velocity as the ordinate to obtain a scatter diagram of capacity vs. velocity.

[0037] A further improvement of the present invention lies in:

[0038] The operation of step (4) includes:

[0039] (41) For each air gun with a certain capacity, substitute the capacity of the air gun into the fitting expression of capacity vs. velocity to obtain the bubble rising velocity;

[0040] (42) Combine the horizontal motion velocity component of the hydrophone with the bubble rising velocity to obtain the relative motion velocity of the bubble of the air gun with this capacity relative to the hydrophone.

[0041] In the second aspect of the present invention, a measurement system for the relative motion velocity of an air gun seismic source bubble is provided. The system includes:

[0042] Horizontal velocity component acquisition unit: used to obtain the course and speed of the seismic source ship and calculate the horizontal motion velocity component of the hydrophone;

[0043] Bubble parameter acquisition unit: used to record the bubble rising time;

[0044] Bubble rising velocity calculation unit: connected to the bubble parameter acquisition unit and used to calculate the bubble rising velocity;

[0045] Relative velocity calculation unit: respectively connected to the horizontal velocity component acquisition unit and the bubble rising velocity calculation unit and used to obtain the relative motion velocity of the bubble relative to the hydrophone.

[0046] In a third aspect of the present invention, there is provided a computer-readable storage medium storing at least one computer-executable program, which when executed by the computer causes the computer to perform the steps in the above method for measuring the relative movement speed of the air gun source bubble.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] 1. The relative movement speed of the bubble excited by the air gun source can be obtained by using the present invention;

[0049] 2. Through actual tests, it is shown that the relative movement speed of the air gun source bubble measured by the present invention can be used for far-field wavelet simulation, and the accuracy and reliability of far-field wavelet simulation are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The block diagram of the steps of the method of the present invention;

[0051] Figure 2 The floating time and floating speed of the air gun bubbles with different capacities;

[0052] Figure 3 The curve fitting diagram of the floating speed of the air gun bubbles with different capacities;

[0053] Figure 4 The relative movement speed of the bubbles with different capacity hydrophones;

[0054] Figure 5-1 The far-field wavelet waveform diagram;

[0055] Figure 5-2 The frequency spectrum diagram of the far-field wavelet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] The present invention will be further described in detail below with reference to the drawings:

[0057] Aiming at the problem that "when simulating the far-field wavelet through the near-field wavelet recorded by the near-field hydrophone of the air gun source in marine seismic exploration, the oscillating bubbles generated after the air gun excitation are not considered to float, and at the same time, during the ship's movement, the position of the hydrophone recording the near field moves with the ship, resulting in the change of the bubble center position and the hydrophone position over time, which brings errors to the accuracy of the far-field wavelet simulation", the present invention proposes a method for measuring the movement speed of the air gun source excited bubble relative to the hydrophone to improve the accuracy of near-field simulation of the far-field wavelet.

[0058] The embodiments of the method of the present invention are as follows:

[0059]

Embodiment 1

[0060] As Figure 1As shown in the figure, the method of the present invention includes:

[0061] (1) Obtain the heading and speed of the seismic source vessel from the navigation record of the seismic source vessel, specifically including:

[0062] (11) Obtain the heading φ of the seismic source vessel from the navigation system of the seismic source vessel nav and the speed v nav ;

[0063] (12) Calculate the horizontal motion speed components v x and v y :

[0064] v x = v nav cosφ

[0065] v y = v nav sinφ

[0066] wherein, v x and v y are the speed components in the x-axis and y-axis directions respectively.

[0067] (2) Measure the floating-up time of air gun bubbles with different volumes, specifically including:

[0068] (21) The surveyor stands at the stern of the ship to observe and record the generation time t 1,i of the bubbles below the sea surface when a single gun with a certain volume is fired ((the generation of bubbles several meters underwater can be observed with the naked eye, and the surveyor can obtain this time by observing and timing with a timer), and the time t 2,i when the bubbles float to the sea surface and disappear. Using t i = t 2,i - t 1,i the floating-up time t i of the air gun bubbles of this volume can be obtained, where i represents the serial number of the air gun;

[0069] (22) Repeat step (21) for all air guns with different volumes in the seismic source array (each air gun with a certain volume is equivalent to a seismic source), and measure the floating-up time of the air gun bubbles of each volume.

[0070] (3) Calculate the floating-up speed of air gun bubbles with different volumes, specifically including:

[0071] (31) Obtain the sinking depth h i of an air gun with a certain volume (this depth is a known quantity and remains fixed);

[0072] (32) Calculate the floating-up speed v z,i of the air gun bubbles: v z,i = h i / t i ;

[0073] (33) Repeat steps (31) and (32) to calculate the upward floating velocities of air gun bubbles of all capacities. Measure the upward floating times of bubbles of different capacities of air guns, and the corresponding upward floating velocities calculated are as Figure 2 shown.

[0074] (34) Draw a scatter plot of capacity vs. velocity based on the upward floating velocities of air gun bubbles of all capacities;

[0075] (35) Perform logarithmic fitting on the scatter plot of capacity vs. velocity to obtain a capacity-velocity fitting expression v z = aln(c) + b, where c is the air gun capacity, and a and b are known coefficients obtained through fitting. Figure 3 is a fitting diagram of the upward floating velocity curve of air gun bubbles of different capacities, and the fitting curve equation is vz = 0.3095ln(c) - 0.0309.

[0076] (4) Obtain the movement velocity of the bubble relative to the hydrophone, specifically including:

[0077] (41) For each capacity of air gun, obtain the known capacity c of the air gun and substitute it into the capacity-velocity fitting expression to obtain the corresponding upward floating velocity v z,i ;

[0078] (42) Combine the movement velocity v x and v y of the hydrophone with v z,i to obtain the movement velocity (v x,i , v y,i , v z,i ) of the air gun bubble relative to the hydrophone. Figure 4 is the horizontal velocity component of the hydrophone recorded in one shot obtained from the navigation data, and is combined with the upward floating velocity of the bubble to form the three components of the movement velocity of the bubble relative to the hydrophone.

[0079]

Embodiment 2

[0080] As Figure 1 shown, the method of the present invention includes:

[0081] (1), Obtain the course and speed of the source ship from the navigation record of the source ship, specifically including:

[0082] (11) Obtain the course φ nav and speed v nav of the source ship from the navigation system of the source ship;

[0083] (12) Calculate the horizontal movement velocity components v x and vy :

[0084] v x = v nav cosφ

[0085] v y = v nav sinφ

[0086] where v x and v y are the velocity components in the x-axis and y-axis directions, respectively.

[0087] (2) Measure the rising time of the bubbles of air guns with different capacities, specifically including:

[0088] (21) The surveyor stands at the stern of the ship to observe and record the generation time t of the bubbles below the sea surface when a single gun of a certain capacity is fired 1,i ((The bubbles generated several meters underwater can be observed with the naked eye. The surveyor can obtain this time by observing and timing with a timer), and the time t when the bubbles disappear after rising to the sea surface 2,i , t i = t 2,i - t 1,i is the rising time of the bubbles of the air gun of this capacity, and i represents the serial number of the air gun;

[0089] (22) Repeat step (21) for all air guns with different capacities in the seismic source array (each air gun with a certain capacity is equivalent to a seismic source), and measure the rising time of the bubbles of each air gun with different capacities. To reduce measurement errors, in this embodiment, step (21) is repeated multiple times for the same air gun, and the average value of the multiple rising times of this air gun is taken as the rising time of the bubbles of this air gun.

[0090] (3) Calculate the rising speed of the bubbles of air guns with different capacities, specifically including:

[0091] (31) Obtain the sinking depth h of an air gun with a certain capacity i (This depth is a known quantity and remains fixed);

[0092] (32) Calculate the rising speed v of the bubbles of this air gun z,i : v z,i = h i / t i ;

[0093] (33) Repeat steps (31) and (32) to calculate the rising speeds of the bubbles of all air guns with different capacities. The measured rising times of the bubbles of air guns with different capacities and the corresponding rising speeds calculated are as Figure 2 shown.

[0094] (34) Plot a scatter diagram of volume - velocity by the upward floating velocity of air - gun bubbles of all volumes: Plot the upward floating velocities of air - gun bubbles of all volumes in a coordinate diagram with volume as the abscissa and upward floating velocity as the ordinate to obtain a volume - velocity scatter diagram.

[0095] (35) Conduct logarithmic fitting on the volume - velocity scatter diagram to obtain a volume - velocity fitting expression \(v\) z \(= a\ln(c)+b\), where \(c\) is the air - gun volume, and \(a\) and \(b\) are known coefficients obtained through fitting. Figure 3 It is the fitting diagram of the upward floating velocity curves of air - guns with different volumes. The fitting curve equation is \(v_z = 0.3095\ln(c)-0.0309\).

[0096] (4) Obtain the moving velocity of the bubble relative to the hydrophone, specifically including:

[0097] (41) For each volume of air - gun, obtain the known volume \(c\) of this air - gun and substitute it into the volume - velocity fitting expression to obtain the corresponding upward floating velocity \(v\) z,i ;

[0098] (42) Combine the moving velocity \(v\) x and \(v\) y of the hydrophone with \(v\) z,i to obtain the moving velocity of the air - gun bubble relative to the hydrophone for this volume \((v\) x,i , \(v\) y,i , \(v\) z,i ). Figure 4 It is the horizontal velocity component of the hydrophone recorded in one shot obtained from navigation data, which is combined with the upward floating velocity of the bubble to form three components of the moving velocity of the bubble relative to the hydrophone.

[0099] Figure 5-1 and Figure 5-2 are the comparison diagrams of the far - field sub - wave calculated with the data of Figure 4 considering the relative moving velocity of the bubble and the far - field sub - wave calculated without considering the moving velocity of the bubble. Among them, Figure 5-1 , the gray curves in Figure 5 - 2 are the waveforms and spectrograms without considering the relative moving velocity of the bubble, and the black curves are the waveforms and spectrograms considering the relative moving velocity of the bubble. From Figure 5-1 , Figure 5-2 it can be seen that after considering the relative moving velocity of the bubble, the shape of the far - field sub - wave is significantly different from that without considering the relative moving velocity of the bubble. At the same time, in the spectrogram shown in Figure 5-2 , after considering the relative moving velocity of the bubble, the low - frequency oscillation amplitude of the spectrum of the far - field sub - wave is larger, which is more in line with the shape of the far - field sub - wave in the actual situation. Specifically, as Figure 5-1 and Figure 5-2As shown by the ellipse in [the figure], the jitter of the sub-wave considering bubble motion at the position marked by the ellipse in the waveform and spectrogram is more severe than that of the sub-wave without considering bubble motion. This jitter is caused by bubble motion. Therefore, the sub-wave considering bubble motion simulates the actual sub-wave form and is more in line with the real situation.

[0100] The present invention also provides a measurement system for the relative motion speed of the air gun source bubble. The embodiments of the system are as follows:

[0101]

Embodiment III

[0102] The system includes:

[0103] Horizontal velocity component acquisition unit: used to acquire the course and speed of the source ship and calculate the horizontal motion speed component of the hydrophone; specifically, the horizontal velocity component acquisition unit obtains the course φ of the source ship from the navigation system of the source ship nav and the speed v nav , and calculates the horizontal motion speed components v x and v y of the hydrophone by using the following formula:

[0104] v x = v nav cosφ

[0105] v y = v nav sinφ

[0106] where v x and v y are the speed components in the x-axis and y-axis directions respectively.

[0107] Bubble parameter acquisition unit: used to record the rising time of the bubble; specifically, the bubble parameter acquisition unit records the generation time t 1,i of the bubble below the sea surface when each capacity single gun is fired and the disappearance time t 2,i of the bubble after it rises to the sea surface, and calculates the rising time t i of the bubble by using the following formula: t i = t 2,i - t 1,i where i represents the serial number of the air gun.

[0108] Bubble rising speed calculation unit: connected to the bubble parameter acquisition unit and used to calculate the rising speed of the bubble. Specifically, the bubble rising speed calculation unit first records the sinking depth h i of each capacity air gun, and then calculates the rising speed v z,i of the bubble of this air gun by using the following formula: v i = h iMeanwhile, the bubble rising velocity calculation unit plots a scatter diagram of volume and velocity based on the rising velocities of the air gun bubbles of all volumes, and performs logarithmic fitting on the scatter diagram of volume and velocity to obtain a fitting expression of volume and velocity.

[0109] Relative velocity calculation unit: connected to the horizontal velocity component acquisition unit and the bubble rising velocity calculation unit respectively, for obtaining the moving velocity of the bubble relative to the hydrophone. Specifically, the relative velocity calculation unit substitutes the volume c of each air gun into the volume-velocity fitting expression to obtain the corresponding bubble rising velocity v z,i , and then combines the moving velocity v x of the hydrophone and v y with v z,i to obtain the moving velocity (v x,i , v y,i , v z,i ) of the air gun bubble relative to the hydrophone for this volume.

[0110] The present invention also provides a computer-readable storage medium, which stores at least one computer-executable program. When the at least one program is executed by the computer, the computer executes the steps in the method for measuring the relative moving velocity of the air gun source bubble as described above.

[0111] The purpose of far-field wavelet simulation is to more realistically simulate the far-field wavelets excited by the actual source array. To simulate the real far-field wavelets, it is necessary to consider the real environment and factors of air gun excitation, and the movement of the bubble is an important factor affecting the air gun wavelet. Therefore, when simulating the far-field wavelets, considering this factor makes the simulated far-field wavelets more real, with higher accuracy and reliability.

[0112] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0113] In the description of the present invention, unless otherwise stated, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0114] Finally, it should be noted that the above technical solutions are only one implementation mode of the present invention. For those skilled in the art, based on the disclosed application methods and principles of the present invention, it is very easy to make various types of improvements or deformations, not limited to the methods described in the above specific implementation modes of the present invention. Therefore, the above-described mode is only preferred and does not have a restrictive meaning.

Claims

1. A method for measuring the relative movement speed of an air gun seismic source bubble, characterized in that: The method obtains the movement speed of the bubble relative to the hydrophone according to the heading and speed of the seismic source vessel and the measured rising time of the bubbles of air guns with different capacities. The method includes: (1) obtaining the heading and speed of the seismic source vessel to obtain the horizontal movement speed component of the hydrophone. (2) Measuring the rising time of the bubbles. (3) Calculating the rising speed of the bubbles, including: (31) Obtain the sinking depth h of the air gun i ; (32) The bubble rising velocity v of this air gun is calculated using the following formula z,i : v z,i = h i / t i where t i is the rising time of the bubble; (33) Repeating steps (31) and (32) to obtain the rising speeds of the bubbles of air guns with all capacities. (34) Plotting a scatter diagram of capacity-rising speed. (35) Performing logarithmic fitting on the scatter diagram of capacity-rising speed to obtain a capacity-speed fitting expression to obtain the rising speed of the bubbles. (4) Obtaining the movement speed of the bubble relative to the hydrophone for far-field wavelet simulation.

2. The method for measuring the relative movement speed of the air gun source bubble according to claim 1, wherein: The operation of step (1) includes: (11) Obtain the heading φ of the seismic source vessel from the navigation system of the seismic source vessel nav and the speed v nav ; (12) Calculating and obtaining the horizontal movement speed component of the hydrophone using the following formula: v x = v nav cosφ nav v y = v nav sin φ nav Among them, v x and v y are the velocity components in the x-axis and y-axis directions respectively.

3. The method for measuring the relative movement speed of the air gun source bubble according to claim 2, wherein: The operation of step (2) includes: (21) Record the generation time \(t\) of the underwater bubbles when the single air gun is fired 1,i , and the disappearance time \(t\) of the bubbles after they float to the sea surface 2,i , and calculate the rising time \(t\) of the bubbles using the following formula i : \(t\) i = \(t\) 2,i - \(t\) 1,i where \(i\) represents the serial number of the air gun; (22) Repeating step (21) for air guns with all capacities to obtain the rising time of the bubbles of each capacity air gun.

4. The method for measuring the relative movement speed of the air gun source bubble according to claim 3, wherein: The operation of step (22) further includes: Repeating the operation of step (21) multiple times for air guns of the same capacity to obtain the rising times of multiple bubbles, and taking the average of the obtained rising times of multiple bubbles as the rising time of the bubbles of this air gun.

5. The method for measuring the relative movement speed of the air gun source bubble according to claim 1, characterized in that: The operation of step (34) includes: Plotting the rising speeds of the bubbles of air guns with all capacities in a coordinate diagram with capacity as the abscissa and rising speed as the ordinate to obtain a scatter diagram of capacity-rising speed.

6. The method for measuring the relative movement speed of the air gun source bubble according to claim 5, characterized in that: The operation of step (4) includes: (41) For each capacity air gun, substituting the capacity of this air gun into the capacity-speed fitting expression to obtain the rising speed of the bubbles. (42) Combining the horizontal movement speed component of the hydrophone with the rising speed of the bubbles to obtain the movement speed of the bubbles of this capacity air gun relative to the hydrophone.

7. A measurement system for the relative movement speed of an air gun seismic source bubble, characterized in that: The system includes: A horizontal speed component acquisition unit: used to obtain the heading and speed of the seismic source vessel to obtain the horizontal movement speed component of the hydrophone. A bubble parameter acquisition unit: used to record the rising time of the bubbles. A bubble rising speed calculation unit: connected to the bubble parameter acquisition unit, used to calculate the rising speed of the bubbles, including: (31) Obtain the sinking depth h of the air gun i ; (32) The bubble rising velocity v of the air gun is calculated using the following formula z,i : v z,i = h i / t i where t i is the rising time of the bubble; (33) Repeating steps (31) and (32) to obtain the rising speeds of the bubbles of air guns with all capacities. (34) Plotting a scatter diagram of capacity-rising speed. (35) Performing logarithmic fitting on the scatter diagram of capacity-rising speed to obtain a capacity-speed fitting expression to obtain the rising speed of the bubbles. A relative speed calculation unit: respectively connected to the horizontal speed component acquisition unit and the bubble rising speed calculation unit, used to obtain the movement speed of the bubble relative to the hydrophone for far-field wavelet simulation.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores at least one computer-executable program, and when the at least one program is executed by the computer, the computer executes the steps in the method for measuring the relative movement speed of the air gun seismic source bubble according to any one of claims 1-6.

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