CN112180435A - Method and device for monitoring position of seismic source towed by auxiliary ship - Google Patents
Method and device for monitoring position of seismic source towed by auxiliary ship Download PDFInfo
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Abstract
The embodiment of the invention provides a method and a device for monitoring the position of a seismic source towed by an auxiliary ship, and belongs to the field of exploration. The method comprises the following steps: acquiring offset distance, shot point water depth and demodulator probe water depth between the shot point position and the demodulator probe position; judging whether the first arrival wave is a direct wave or a refracted wave according to the offset distance, the shot point water depth and the demodulator probe water depth; if the first-motion wave is a direct-motion wave, correcting the first-motion time of the first-motion wave by using the first-motion time of the direct-motion wave, otherwise, correcting the first-motion time of the first-motion wave by using the first-motion time of the refracted wave; and judging whether the position of the seismic source towed by the auxiliary ship is abnormal or not according to the corrected first arrival time of the first arrival wave. The method can realize accurate correction of the first arrival time of the first arrival wave, thereby providing accurate basis for judging whether the position of the seismic source towed by the auxiliary ship is abnormal.
Description
Technical Field
The invention relates to the field of exploration, in particular to a method and a device for monitoring the position of a seismic source towed by an auxiliary ship.
Background
The multi-ship multi-source wide-azimuth operation is generally mainly controlled by a main ship, real-time navigation information of an auxiliary ship towing a seismic source is displayed on the main ship, the main ship simultaneously controls the auxiliary ship to tow a seismic source gun array and a ship gun array, and data and control instructions need to be transmitted through a wireless communication system between the two ships. The ship navigation state control (including speed control of a main ship and an auxiliary ship, navigation distance, survey line deviation control and the like) is a main factor for restricting whether satisfactory data can be obtained or not in field acquisition of multi-ship earthquake acquisition items, and the importance of authenticity monitoring of multi-ship multi-source earthquake source positions is also reflected, so that the establishment of an effective monitoring method for the wide-azimuth multi-source earthquake acquisition earthquake source positions is particularly important.
The LMO (linear motion out) method is used for monitoring the position of a seismic source, wherein a time correction value is obtained by using offset data measured by a navigation acoustic network system and the sound wave propagation speed in water, and the seismic record data is corrected by using the time correction value. If the time correction value obtained by the offset distance measured by navigation and the propagation speed of the sound wave in the water is consistent with the first arrival time of the seismic record, the corrected first arrivals of the data are all at the zero moment of the time axis. The seismic data are wholly shifted down for some time (for example, the shift-down time can be 300ms) in the actual production process, and the abnormal points can be visually observed. As shown in FIG. 1, the fourth trace per cable of the left source of the seismic source towed by the main ship is corrected by using a linear dynamic correction method, and the data uses the fourth trace single-trace seismic data per cable of an SEQ022 survey line. Wherein: SP _ NB represents the shot number, SP _ MASK represents the source number, 1 is the left source, 2 is the right source, 3 is the auxiliary ship towing source, ACQ _ CABLENB is the cable number, and the offset can be obtained from the heading OFF _ NB. And (3) correcting the corrected first arrival time of the fourth track of every 10 cables to a 300ms time axis, and if the position of the corresponding shot point on the time axis is not described, possibly having an abnormality, needing navigation to process the data again.
When the position of the seismic source towed by the auxiliary ship is monitored by using a conventional linear dynamic correction method, all selected parameters are consistent with those of the main ship. Ideally, the correction result should be consistent with the monitoring result of the source position of the main ship, however, in the case that the auxiliary ship towing source position information is correct, the actual correction effect is the same as the result shown in fig. 2, and some abnormal phenomena such as the following occur:
(1) there is a lot of random jitter in the first arrival time;
(2) the time of first arrival is not corrected to the theoretical 300ms position;
(3) the corrected first arrival time of the fourth pass corresponding to each cable is not on the uniform time axis.
The phenomena do not exist in a measuring line of SEQ022, but exist in the whole work area, so the original linear dynamic correction method is not suitable for monitoring the position of the auxiliary ship towing seismic source in the wide-azimuth multi-source seismic acquisition. A set of convenient, effective and visual monitoring method for the position of an auxiliary ship towing seismic source needs to be researched according to the uniqueness of the auxiliary ship towing seismic source in a wide-azimuth multi-source seismic acquisition.
Disclosure of Invention
The embodiment of the invention aims to provide a method and a device for monitoring the position of a seismic source towed by an auxiliary ship, which can conveniently, effectively and visually monitor the position of the seismic source towed by the auxiliary ship.
In order to achieve the above object, an embodiment of the present invention provides a method for monitoring the position of a seismic source towed by an auxiliary vessel, where the method includes: acquiring offset distance, shot point water depth and demodulator probe water depth between the shot point position and the demodulator probe position; judging whether the first arrival wave is a direct wave or a refracted wave according to the offset distance, the shot point water depth and the demodulator probe water depth; if the first-motion wave is a direct-motion wave, correcting the first-motion time of the first-motion wave by using the first-motion time of the direct-motion wave, otherwise, correcting the first-motion time of the first-motion wave by using the first-motion time of the refracted wave; and judging whether the position of the seismic source towed by the auxiliary ship is abnormal or not according to the corrected first arrival time of the first arrival wave.
Correspondingly, the embodiment of the invention also provides a device for monitoring the position of a seismic source towed by an auxiliary ship, which comprises: the acquisition module is used for acquiring the offset distance between the shot point position and the wave detection point position, the shot point water depth and the wave detection point water depth; the first judgment module is used for judging whether the first arrival wave is a direct wave or a refracted wave according to the offset distance, the shot point water depth and the demodulator probe water depth; the correction module is used for correcting the first-arrival time of the first-arrival wave by using the first-arrival time of the direct wave if the first-arrival wave is the direct wave, and otherwise, correcting the first-arrival time of the first-arrival wave by using the first-arrival time of the refracted wave; and the second judgment module is used for judging whether the position of the seismic source towed by the auxiliary ship is abnormal or not according to the corrected first arrival time of the first arrival wave.
Accordingly, embodiments of the present invention also provide a machine-readable storage medium having stored thereon instructions for causing a machine to perform the method for monitoring the position of a seismic source towed by an auxiliary vessel as described above.
Through the technical scheme, whether the first arrival wave is the direct arrival wave or the refracted wave is judged according to the difference of the offset distances, the first arrival time of the first arrival wave is corrected by using the first arrival time of the direct arrival wave or the refracted wave, accurate correction of the first arrival time of the first arrival wave can be achieved, and therefore accurate basis is provided for judging whether the position of the seismic source towed by the auxiliary ship is abnormal.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:
FIG. 1 is a schematic diagram showing the effect of using a linear dynamic correction method to correct the fourth trace per cable of the left source towing a seismic source by a host vessel;
FIG. 2 is a schematic diagram showing the effect of using a linear dynamic correction method to correct an auxiliary source vessel;
FIG. 3 illustrates a flow diagram of a method for monitoring the position of a seismic source towed by a secondary vessel in accordance with an embodiment of the present invention;
FIG. 4 shows a schematic diagram of the geometric path of refracted waves of a seafloor geological model;
fig. 5 to 8 are schematic diagrams respectively showing time distance curves of refracted waves in different embodiments;
figure 9 shows a schematic representation of the validation of the method provided by embodiments of the invention on the SEQ018 line;
FIGS. 10-12 are schematic diagrams showing the results of the correction of the main ship towing seismic source and the auxiliary ship towing seismic source by the method provided by the embodiment of the invention in SEQ017 survey lines, respectively;
FIGS. 13-15 are schematic diagrams showing the results of the correction of the main ship towing seismic source and the auxiliary ship towing seismic source by the method provided by the embodiment of the invention in SEQ018 line, respectively; and
FIG. 16 is a block diagram of an apparatus for monitoring the position of a seismic source towed by a secondary vessel, according to an embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.
In the marine wide-azimuth multi-source exploration process, an auxiliary ship towing seismic source and a cable detector are often far away (mostly more than 1000m), when the water depth is shallow, direct waves are researched, the direct waves are often found to be incapable of reaching the detector firstly, and corresponding first arrival waves are possibly refracted waves, so that the traditional LMO method cannot meet the production requirement. Based on the method, the embodiment of the invention provides a method for conveniently, effectively and visually monitoring the position of the seismic source of the auxiliary ship towing belt.
FIG. 3 shows a flow diagram of a method for monitoring the position of a seismic source towed by a secondary vessel, in accordance with an embodiment of the present invention. As shown in fig. 3, an embodiment of the present invention provides a method for monitoring the position of a seismic source towed by a secondary vessel, which may include steps S310 to S340.
And S310, acquiring the offset distance between the shot point position and the wave detection point position, the shot point water depth and the wave detection point water depth.
The offset may be obtained from a seismic processing system, which may be, for example, a geovement seismic processing system. The offset may be acquired in real time. The shot depth may be obtained by de-encoding the SEGD data of the geoveation seismic processing system. The depth of the water at the wave detection point can be obtained by calculating the water depth data of the main ship.
And S320, judging whether the first arrival wave is a direct wave or a refracted wave according to the offset distance, the shot point water depth and the demodulator probe water depth.
Step S330, if the first-motion wave is a direct-motion wave, the first-motion time of the first-motion wave is corrected by using the first-motion time of the direct-motion wave, otherwise, the first-motion time of the first-motion wave is corrected by using the first-motion time of the refracted wave.
Step S340, judging whether the position of the seismic source towed by the auxiliary ship is abnormal according to the corrected first arrival time of the first arrival wave.
In the case of different offsets, the types of first arrival waves may be different. According to the difference of the offset distances, whether the first-arrival wave is the direct wave or the refracted wave is judged, and then the first-arrival time of the first-arrival wave is corrected by using the first-arrival time of the direct wave or the refracted wave, so that the first-arrival time of the first-arrival wave can be accurately corrected, and an accurate basis is provided for judging whether the position of the seismic source towed by the auxiliary ship is abnormal. Specifically, in the case where the first arrival time of the first arrival wave is corrected correctly, if the first arrival time of the first arrival wave is jittered, it is possible to determine that the position of the seismic source towed by the auxiliary ship is abnormal.
The principle of the present invention will be described below, which mainly involves analyzing time-distance curves of a direct wave and a refracted wave under different offset distances and different depths, and selecting different quality control modes according to different characteristics of the time-distance curves.
The primary condition for forming a refracted wave is that the layer velocity of the overlying medium of the interface is less than the layer velocity of the underlying medium. During marine exploration, the velocity of the sea bottom is the velocity of seismic waves propagating in a seabed medium (such as seabed sediment) (about 1600-1900 m/s, different seabed medium velocities), and the velocity of the water is the velocity of seismic waves propagating in the water (about 1490-1560 m/s, seawater velocity can float under different temperatures and salinity), so that the formation condition of refracted waves is completely met. The first arrival time of the direct arrival wave at the wave detection point is the propagation speed of the seismic wave in the seawater on the offset ratio, and the first arrival time and the offset are in a linear relation. Next, the first-arrival time of the refracted wave is analyzed with emphasis on which variables are affected, and particularly how changes in the first-arrival time are affected.
For simplicity, a refracted wave is used as an analysis object, and a time distance curve between the first arrival time and the offset distance of the refracted wave is analyzed. Fig. 4 shows a schematic diagram of the geometric path of refracted waves of a seafloor geological model. The seabed may have two conditions of upward inclination excitation and downward inclination excitation (the depth of the water at the wave detection point is greater than that of the water at the shot point), wherein the upward inclination excitation refers to the condition that the depth of the water at the wave detection point is less than that of the water at the shot point, and the downward inclination excitation refers to the condition that the depth of the water at the wave detection point is greater than that of the water at the shot point. The demodulator probe water depth refers to the depth of the sea water at the demodulator probe (the vertical distance from the sea surface to the sea floor), and the shot point water depth refers to the depth of the sea water at the seismic source. The following tilt excitation is described as an example in connection with fig. 4.
From the geometrical relationship shown in fig. 4, it can be seen that when the propagation paths of the refracted wave to the detection point in the down tilt excitation are SA, AB, and BR, the first arrival time t of the refracted wave-Can be expressed as formula (1):
from the geometric relationships in fig. 4, and substituting the known variables into equation (1), equation (1) can be rewritten as equation (2):
formula (2) can be simplified to formula (3) through algebraic operation, and formula (3) can be expressed as a time-distance curve of refracted waves:
in the embodiment of the invention, x is the offset distance, dsDepth of shot point water, dRThe depth of the water at the wave detection point,
for refracting inclination, i.e. inclination of sea floor to horizontal, VbIs the velocity, V, of seismic waves propagating in the seabed mediumwIs the velocity of seismic waves propagating in water, and theta is the critical angle of refracted waves.
According to the refraction principle, the critical angle and the propagation velocity of the upper and lower layers of media of the interface have the following relationship:
replacing the critical angle theta with the water medium velocity and the seabed velocity and using T-、k-The slope and intercept of the time-distance curve expressed by the formula (3) are expressed, and the following relationship can be obtained after simplification:
handle k-The following relationship is obtained by simplification:
substituting the formulas (5) and (7) into the formula (3) can obtain the first arrival time t of the refracted wave when the seismic source is excited in a declination way-The calculation formula of (2):
according to the same principle as the seismic source downdip excitation, the first arrival time t of the refracted wave can be obtained when the seismic source is excited by the upward dip+The calculation formula of (2):
equation (9) may represent the time-distance curve of the refracted wave when the seismic source is excited with an upward inclination. By T+、k+Representing the slope and intercept of the time-distance curve represented by equation (9), the following relationship can be obtained:
substituting equations (10) and (11) into equation (9) yields:
from the geometry of FIG. 4, the refraction tilt angle can be obtained
Depth d from shot pointsDepth d of sum-point waterRThe following relationships exist:
the first arrival time of the refracted wave reaching the detector when the seismic source is excited in a declination mode can be calculated by combining the formulas (8) and (13). The first arrival time of the refracted wave reaching the detector when the seismic source is excited in an upward inclining mode can be calculated by combining the formula (12) and the formula (13).
If the surface geological conditions of the sea bottom do not change greatly, the speed of the seismic waves propagating in the sea bottom medium can be considered to be approximately constant, i.e. VbCan be considered a constant. The speed of seismic wave propagation in water generally varies with salinity and temperature, and does not change much basically in a construction period, namely VwMay also be considered a constant. The depth of water at the shot point and the depth of water at the geophone point tend to change with the shot position, so dsAnd dRThe time-distance curves of the refracted waves are all variables. The distance between the source and the geophone points also tends to vary during production, so x is also a variable in the time-distance curve of the refracted wave. In summary, when the seabed surface geological conditions do not change greatly, the time-distance curve of the refracted wave has three variables, namely the shot point water depth and the demodulator probe water depthDegree, offset. When the bottom layer geological conditions of the seabed surface change, the speed of seismic waves propagating in the seabed medium becomes a variable.
Fig. 5 to 8 are schematic diagrams showing time-distance curves of refracted waves in different embodiments, respectively. Fig. 5 is a time-distance curve of the first arrival time varying with the offset, assuming that the seabed refraction inclination is fixed and the depth of the shot point water is constant, wherein the downward inclination of the seismic source is observed from left to right, and the upward inclination of the seismic source is observed from right to left). Fig. 6 is a time-distance curve of the first arrival time varying with the offset distance under the condition that the seabed refraction inclination angle is 0 and the shot depth is constant when the seismic source is excited in a declination mode, wherein the water depth is 80m, the refraction inclination angle is 0, the seismic wave propagation speed in the seabed medium is 1700m/s, and the seismic wave propagation speed in the water is 1500 m/s. As shown in fig. 7, the time-distance curve is a time-distance curve in which the first arrival time varies with the depth of the shot point water under the assumption that the offset distance and the seabed refraction inclination angle are not changed, wherein the refraction inclination angle is 0, the offset distance is 1000, the seismic wave has a propagation speed of 1700m/s in the seabed medium, and the seismic wave has a propagation speed of 1500m/s in water. As shown in fig. 8, it is assumed that the offset distance is constant, the shot depth is constant, and the time distance curve of the refracted wave corresponding to the variation of the seabed refraction inclination angle is assumed that the seabed depth is 80m, the offset distance is 1000m, the seismic wave propagation speed in the seabed medium is 1700m/s, and the seismic wave propagation speed in water is 1500 m/s.
Velocity of sound V in seawaterwIt can be obtained by a navigated sound velocimeter measurement, which can be considered as a constant. Depth of shot dsMay be obtained by de-compiling SEGD data. Depth d of wave detection point waterRCan be obtained by the water depth data of the main ship. Each source and geophone offset x may be obtained by combining the navigation data with the seismic data and may be recorded in the seismic data trace header. That is, three environmental variables of shot point water depth, demodulator probe water depth and offset distance can be obtained in real time. Velocity V of seismic waves propagating in a seabed mediumbIs an unknown quantity but can be obtained by calculation. In the specific calculation, the refraction inclination angle can be calculated through the bulletin (13)
Reading at least one correct first arrival time on a single shot record on each survey line, calculating a critical angle theta of a refracted wave according to a formula (3) or a formula (9), and finally calculating the propagation speed V of the seismic wave in the seabed medium according to a formula (4)b. Calculate VbLater, it may be considered as a constant in one trip. The three environmental variables of shot point water depth, demodulator probe water depth and offset are simultaneously corrected to obtain accurate refracted wave correction time, and the seismic data are corrected by using the accurate refracted wave correction time. By using the method for correction, accurate correction data can be obtained, and the position information of the seismic source towed by the auxiliary ship can be visually monitored.
Further, as can be seen from fig. 5, the time distance curve of the direct wave and the time distance curve of the refracted wave have an intersection point, if the offset x is before the intersection point, the direct wave is the first-arrival wave, and if the offset x is after the intersection point, the refracted wave is the first-arrival wave. The first arrival time of the direct wave is the propagation speed of the seismic wave in the sea water at the offset ratio. The calculation formula of the intersection point can be obtained by solving the calculation formula of the first arrival time of the direct wave and the calculation formula of the first arrival time of the refracted wave.
Through calculation, for the downdip condition (the depth of the demodulator probe water is greater than that of the shot point water), the offset distance A at the intersection point-The calculation formula of (2) is as follows:
for the tilt-up case (the depth of the probe point water is not greater than that of the shot point water), the offset A is arranged at the intersection point+The calculation formula of (2) is as follows:
the offset A at the intersection can be calculated at any time according to equation (13) or (14)+If, ifAnd if the current offset distance is smaller than the offset distance at the intersection point, the first-motion wave is a direct wave, otherwise, the first-motion wave is a refracted wave. The method can realize accurate correction of the first arrival time of the first arrival wave, thereby providing accurate basis for judging whether the position of the seismic source towed by the auxiliary ship is abnormal.
In actual operation, the method provided by the embodiment of the invention can be applied to a geoveation seismic processing system to solve problems in actual production, and the method can be used for building a model of the method provided by the embodiment of the invention on the system. The depth d of the shot point water is needed in the process of decoding SEGD data by using a processing systemsThe solution is compiled, and in addition, some self-defined track head information needs to be defined, and the corresponding inner track head of the geover seismic processing system in formula (8), formula (12) and formula (13) needs to be known, wherein x corresponds to OFF _ NB track head, d corresponds to OFF _ NB track headSCorresponding to SP _ WDEPTH way header, dRThere is no corresponding data in the seismic data, and it is necessary to estimate by the water depth data of the host vessel and construct corresponding heading information. And (3) constructing function models corresponding to the formula (8), the formula (12) and the formula (13) by utilizing a custom function HMATH module of the geo-seismic processing system (the module can construct a mathematical model for specific data according to the requirements of a processor). The seabed velocity V is changed due to the change of seabed surface layer geological conditions on different measuring linesbThe accuracy of the constructed mathematical model is verified on the seismic record data because the mathematical model can change along with the change of different measuring lines.
Figure 9 shows a schematic representation of the validation of the method provided by embodiments of the invention on line SEQ 018. As shown in fig. 9, the mathematical model constructed on the processing system is verified on the measuring line SEQ018, the selected verification data is the near-path single-channel data of the 5 th cable, the line 91 is the first arrival time of the direct wave to the detector calculated by the mathematical model, the line 92 is the first arrival time of the refracted wave to the detector calculated by the mathematical model, and the uppermost curve is the water depth change curve corresponding to the shot point. The calculation value of the mathematical model of the seismic source towed by the main ship or the seismic source towed by the auxiliary ship is completely matched with the seismic data actually produced, so the constructed mathematical model can be well used in the actual production process.
After one survey line verifies the accuracy of the mathematical model, the next step is to determine whether to use the direct wave model or the refracted wave model to correct the seismic data. The time distance curve of the refracted wave and the direct wave described in fig. 5 can be used to obtain the intersection point of the refracted wave and the direct wave on the time axis, the time of the direct wave and the refracted wave reaching the detection point is calculated according to the established mathematical model and recorded into different self-defined track heads, then the IFTHN module (similar to the programmed judgment statement) in the geo is used to judge which of the first-arrival waves is, and different correction models are executed according to the judgment result.
The survey lines SEQ017 and SEQ018 were monitored using the method for monitoring the position of the seismic source towed by the auxiliary vessel provided by the embodiment of the present invention. The seismic data is first shifted down by 500ms and corrected with the navigation data using the first pass of each cable. FIGS. 10-12 are schematic diagrams showing the results of the correction of the main ship towing seismic source and the auxiliary ship towing seismic source by the method provided by the embodiment of the invention in SEQ017 survey lines, respectively; fig. 13-15 show schematic diagrams of the results of the correction of the main ship towing seismic source, the auxiliary ship towing seismic source by the method provided by the embodiment of the invention in SEQ018 survey lines. The monitoring effect graph of the auxiliary ship towing seismic source is almost consistent with the left and right source monitoring effect graph of the main ship towing seismic source, so that the phenomenon of first arrival jitter of the auxiliary ship towing seismic source is eliminated; correcting the first arrival time of the auxiliary ship towing seismic source excitation record to the theoretical first arrival time; the first arrival time of each cable initial road recorded by the seismic source excitation carried by the auxiliary ship is corrected to a uniform time axis. The accuracy of the auxiliary ship towing seismic source position information can be judged by directly observing whether the corrected data has jitter from the beginning to the top, and if the data has jitter from the beginning (such as zigzag) or some shot points are not on the theoretical time axis, the position of the auxiliary ship towing seismic source can be judged to be wrong. The intuitive judgment of the method for monitoring the position of the seismic source towed by the auxiliary ship provided by the embodiment of the invention is mainly suitable for the situation that the seabed between the position of the seismic source towed by the auxiliary ship and the detector is horizontal and inclined (basically meeting the actual production requirement), the method is not used for the extremely rugged seabed, and if the extremely rugged seabed is met, a processor needs to perform special analysis aiming at special conditions, and the accuracy of the information of the position of the seismic source towed by the auxiliary ship cannot be simply judged through the condition that whether the primary arrival time shakes.
According to the method for monitoring the position of the seismic source towed by the auxiliary ship, provided by the embodiment of the invention, the monitoring effect graph of the seismic source towed by the auxiliary ship is almost consistent with the monitoring effect graphs of the left source and the right source of the seismic source towed by the main ship, so that the phenomenon of first arrival jitter of the seismic source towed by the auxiliary ship is eliminated; correcting the first arrival time of the excitation record of the seismic source towed by the auxiliary ship to the theoretical first arrival time; the first arrival time of each cable initial path recorded by the seismic source excitation towed by the auxiliary ship is corrected to a uniform time axis. The method can directly observe whether the corrected data has jitter from the beginning to the top to judge the accuracy of the auxiliary ship towing seismic source position information, and can judge that the auxiliary ship towing seismic source position is abnormal or wrong if the data has jitter from the beginning to the top or some shot points are not on the theoretical time axis.
FIG. 16 is a block diagram of an apparatus for monitoring the position of a seismic source towed by a secondary vessel, according to an embodiment of the present invention. As shown in fig. 16, an embodiment of the present invention further provides a device for monitoring the position of a seismic source towed by a secondary vessel, which may include: an obtaining module 610, configured to obtain an offset between a shot position and a geophone position, a shot depth of water, and a geophone depth of water; a first judging module 620, configured to judge whether the first arrival wave is a direct arrival wave or a refracted wave according to the offset distance, the shot point water depth, and the demodulator probe water depth; a correcting module 630, configured to correct the first-arrival time of the first-arrival wave using the first-arrival time of the direct wave if the first-arrival wave is the direct wave, and otherwise correct the first-arrival time of the first-arrival wave using the first-arrival time of the refracted wave; and a second judging module 640, configured to judge whether the position of the seismic source towed by the auxiliary vessel is abnormal according to the corrected first arrival time of the first arrival wave. In the case of different offsets, the types of first arrival waves may be different. According to the difference of the offset distances, whether the first-arrival wave is the direct wave or the refracted wave is judged, and then the first-arrival time of the first-arrival wave is corrected by using the first-arrival time of the direct wave or the refracted wave, so that the first-arrival time of the first-arrival wave can be accurately corrected, and an accurate basis is provided for judging whether the position of the seismic source towed by the auxiliary ship is abnormal.
The specific working principle and benefits of the device for monitoring the position of the seismic source towed by the auxiliary ship provided by the embodiment of the invention are similar to those of the method for monitoring the position of the seismic source towed by the auxiliary ship provided by the embodiment of the invention, and are not described again here.
Accordingly, embodiments of the present invention also provide a machine-readable storage medium having stored thereon instructions for causing a machine to perform the method for monitoring the position of a seismic source towed by an auxiliary vessel as described above.
Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the embodiments of the present invention are not limited to the details of the above embodiments, and various simple modifications can be made to the technical solutions of the embodiments of the present invention within the technical idea of the embodiments of the present invention, and the simple modifications all belong to the protection scope of the embodiments of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. In order to avoid unnecessary repetition, the embodiments of the present invention do not describe every possible combination.
Those skilled in the art will understand that all or part of the steps in the method according to the above embodiments may be implemented by a program, which is stored in a storage medium and includes several instructions to enable a single chip, a chip, or a processor (processor) to execute all or part of the steps in the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
In addition, any combination of various different implementation manners of the embodiments of the present invention is also possible, and the embodiments of the present invention should be considered as disclosed in the embodiments of the present invention as long as the combination does not depart from the spirit of the embodiments of the present invention.
Claims (11)
1. A method of monitoring the position of a seismic source towed by a vessel, the method comprising:
acquiring offset distance, shot point water depth and demodulator probe water depth between the shot point position and the demodulator probe position;
judging whether the first arrival wave is a direct wave or a refracted wave according to the offset distance, the shot point water depth and the demodulator probe water depth;
if the first-motion wave is a direct-motion wave, correcting the first-motion time of the first-motion wave by using the first-motion time of the direct-motion wave, otherwise, correcting the first-motion time of the first-motion wave by using the first-motion time of the refracted wave; and
and judging whether the position of the seismic source towed by the auxiliary ship is abnormal or not according to the corrected first arrival time of the first arrival wave.
2. The method of claim 1, wherein the first arrival time of the refracted wave is calculated according to the following:
if the depth of the water at the wave detection point is greater than that of the water at the shot point, calculating the first arrival time t of the refracted wave by using the following formula-：
If the depth of the water at the wave detection point is not greater than the depth of the water at the shot point, calculating the first arrival time t of the refracted wave by using the following formula+：
Wherein the content of the first and second substances,
wherein x isSaid offset distance, dsDepth of shot point water, dRThe depth of the water at the wave detection point,
is a refractive angle of inclination, VbIs the velocity, V, of seismic waves propagating in the seabed mediumwIs the velocity of seismic waves propagating in water.
3. The method of claim 1, wherein the determining whether the first arrival wave is a direct wave or a refracted wave according to the offset distance, the shot point water depth, and the geophone point water depth comprises:
calculating a first distance; and
if the offset distance is smaller than the first distance, the first-arrival wave is a direct arrival wave, otherwise, the first-arrival wave is a refracted wave.
4. The method of claim 3, wherein the first distance is calculated according to the following:
if the depth of the water at the wave detection point is greater than that of the water at the shot point, the first distance A is calculated by using the following formula-：
If the depth of the water at the wave detection point is not greater than the depth of the water at the shot point, the first distance A is calculated by using the following formula+：
Wherein:
wherein x is the offset distance, dsDepth of shot point water, dRThe depth of the water at the wave detection point,
is a refractive inclination angle, VbIs the velocity, V, of seismic waves propagating in the seabed mediumwIs the velocity of seismic waves propagating in water.
5. The method of any one of claims 1 to 4, wherein the determining whether the location of the seismic source towed by the secondary vessel is abnormal according to the corrected first arrival time of the first arrival wave comprises:
and if the first arrival time of the corrected first arrival waves shakes, judging that the position of the seismic source towed by the auxiliary ship is abnormal.
6. An apparatus for monitoring the position of a seismic source towed by a vessel, the apparatus comprising:
the acquisition module is used for acquiring the offset distance between the shot point position and the wave detection point position, the shot point water depth and the wave detection point water depth;
the first judgment module is used for judging whether the first arrival wave is a direct wave or a refracted wave according to the offset distance, the shot point water depth and the demodulator probe water depth;
the correction module is used for correcting the first-arrival time of the first-arrival wave by using the first-arrival time of the direct wave if the first-arrival wave is the direct wave, and otherwise, correcting the first-arrival time of the first-arrival wave by using the first-arrival time of the refracted wave; and
and the second judging module is used for judging whether the position of the seismic source towed by the auxiliary ship is abnormal or not according to the corrected first arrival time of the first arrival wave.
7. The apparatus of claim 6, further comprising a calculation module for calculating the first arrival time of the refracted wave according to:
if the depth of the water at the wave detection point is greater than that of the water at the shot point, calculating the first arrival time t of the refracted wave by using the following formula-：
If the depth of the water at the wave detection point is not greater than the depth of the water at the shot point, calculating the first arrival time t of the refracted wave by using the following formula+：
Wherein the content of the first and second substances,
wherein x is the offset distance, dsDepth of shot point water, dRThe depth of the water at the wave detection point,
is a refractive angle of inclination, VbIs the velocity, V, of seismic waves propagating in the seabed mediumwIs the velocity of seismic waves propagating in water.
8. The apparatus according to claim 6, wherein the first determining module is configured to determine whether the first arrival wave is a direct arrival wave or a refracted wave according to the following:
calculating a first distance; and
if the offset distance is smaller than the first distance, the first-arrival wave is a direct arrival wave, otherwise, the first-arrival wave is a refracted wave.
9. The apparatus of claim 8, wherein the first determining module calculates the first distance according to:
if the depth of the water at the wave detection point is greater than that of the water at the shot point, the first distance A is calculated by using the following formula-：
If the depth of the water at the wave detection point is not greater than the depth of the water at the shot point, the first distance A is calculated by using the following formula+：
Wherein:
wherein x is the offset distance, dsDepth of shot point water, dRThe depth of the water at the wave detection point,
is a refractive inclination angle, VbIs the velocity, V, of seismic waves propagating in the seabed mediumwIs the velocity of seismic waves propagating in water.
10. The apparatus of any of claims 6 to 9, wherein the second determining module is configured to determine whether the location of the seismic source towed by the tender vessel is abnormal according to:
and if the first arrival time of the corrected first arrival waves shakes, judging that the position of the seismic source towed by the auxiliary ship is abnormal.
11. A machine-readable storage medium having stored thereon instructions for causing a machine to perform the method of position monitoring of a seismic source towed by a tender according to any one of claims 1 to 5.
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