WO2017221070A1

WO2017221070A1 - Marine system and method for acquiring seismic data in prohibited areas with infrastructure by steering a beam of energy

Info

Publication number: WO2017221070A1
Application number: PCT/IB2017/000918
Authority: WO
Inventors: Mickael Landais; Risto Siliqi
Original assignee: Cgg Services Sas
Priority date: 2016-06-23
Filing date: 2017-06-12
Publication date: 2017-12-28

Abstract

A marine seismic acquisition system (400) includes a vessel (402) towing an impulsive source array (404), wherein the impulsive source array (404) includes air guns; a vibratory source array (430) including plural vibratory source elements (432); plural seismic receivers (412) configured to receive and record seismic energy emitted by the impulsive source array and the vibratory source array; and a controller (440) configured to steer a beam of energy formed by the plural vibratory source elements (432). The controller (440) drives the plural vibratory source elements (432) to steer the beam of energy to illuminate an area of interest (426) over which the impulsive source array (404) is prohibited to pass.

Description

MARINE SYSTEM AND METHOD FOR ACQUIRING SEISMIC DATA IN PROHIBITED AREAS WITH INFRASTRUCTURE BY STEERING A BEAM OF ENERGY

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of priority under 35 U.S.C. § 1 19(e) to U.S. Provisional Application No. 62/353,636 filed on June 23, 2016. The entire contents of this document is hereby incorporated by reference into the present application.

BACKGROUND

TECHNICAL FIELD

[0002] Embodiments of the subject matter disclosed herein generally relate to methods and systems related to seismic exploration and, more particularly, to mechanisms and techniques for generating seismic waves with a mixture of vibratory elements and impulsive elements.

DISCUSSION OF THE BACKGROUND

[0003] Marine seismic data acquisition and processing generate a profile (image) of a geophysical structure under the seafloor. This image is generated based on recorded seismic data. The recorded seismic data includes pressure and/or particle motion related data associated with the propagation of a seismic wave through the earth. While this profile does not provide an accurate location of oil and gas reservoirs, it suggests, to those trained in the field, the presence or absence of these reservoirs. Thus, providing a high-resolution image of geophysical structures under the seafloor is an ongoing process. The image illustrates various layers that form the surveyed subsurface of the earth.

[0004] During a seismic gathering process, as shown in Figure 1 , a vessel 1 10 tows an array of seismic receivers 1 1 1 provided on streamers 1 12. The streamers may be disposed horizontally, i.e., lying at a constant depth relative to the ocean surface 1 14, or may have spatial arrangements other than horizontal, e.g., variable- depth arrangement. Vessel 1 10 also tows a seismic source array 1 16 configured to generate seismic waves 1 18 (only one is shown for simplicity). The seismic wave 1 18 propagates downward, toward the seafloor 120, and penetrates the seafloor until, eventually, a reflecting structure 122 (reflector) reflects the seismic wave. The reflected seismic wave 124 propagates upward until it is detected by receiver 1 1 1 on streamer 1 12. Based on this data, an image of the subsurface is generated.

[0005] A traditional impulsive source array may include one or more sub- arrays (usually three sub-arrays), and each sub-array may include plural source elements (e.g., an air gun or a cluster, association of several air guns, etc.). This impulsive source array has better characteristics than existing source arrays and it is disclosed in Patent Application No. 13/468,589, filed on May 10, 2012, and assigned to the same assignee as the present application, the entire disclosure of which is incorporated herein by reference. A source element may be an air gun, i.e., a device that compresses air in a given cavity and, when instructed, suddenly releases the compressed air to create seismic waves.

[0006] Figure 2 shows in more detail a sub-array 200 of such impulsive source array. Sub-array 200 includes a float 202 from which multiple plates 204 are suspended at a given depth. Float 202 has a body that extends along a longitudinal axis (X). Cables 206 may be used to suspend the plates 204 from the float 202. Plural source elements 208a to 208e (i.e., air guns) form the given depth sub-array set 208. All these source elements are suspended from the same float 202 via links 212 that substantially extend along a vertical axis (Z). Link 212 may include a chain, a rope and/or a cable. Each source element may have its own cables 214 (electrical, compressed air, data, etc.) for receiving commands or power (note that these cables are not shown for all the sources). The cables are protected by a rigid housing 215. Strength members 210 may be located between the plates 204 for maintaining the source's integrity when towed underwater.

[0007] A front portion of the plate 204 corresponding to the first source element 208e (an air gun in this figure) may also be connected via a connection 218 to an umbilical 220 that may be connected to the vessel (not shown). Optionally, a link 222 may connect the float 202 to the umbilical 220. In one application, three or more such floats 202 and corresponding source elements may form the source array.

[0008] As seen from this description, the traditional impulsive source arrays are bulky, heavy, difficult to control and not flexible, i.e., the various source elements that make up the source array cannot move independent of the others. For this reason, when one or more obstacles are encountered by the towing vessel, some information (coverage) around the targeted area can be missed because the receivers are not at the right position to detect the returning energy, as illustrated in Figure 3A. Figure 3A shows obstacle 300, which is usually man-made, such as drilling rigs or production facilities, the coverage 304 obtained around the obstacle 300 and the lack of coverage 302 in the immediate vicinity of the obstacle. This lack of coverage happens because neither the source array, nor the streamer(s) are allowed to get very close to the obstacle, for safety concerns.

[0009] Undershooting is a technique used to image the sub-surface beneath obstructions, and is one of the techniques used to better the image in areas of complex geology, as illustrated in Figure 3B. During an undershoot acquisition, one vessel acts as the streamer and recording vessel and a second vessel, that tows a second impulsive source array, provides the source energy for covering area 302.

[0010] For obstructions located close to the subsurface, such as production facilities, a reservoir monitoring program is usually put in place and requires a higher data density and good repeatability of source signal than single towed streamer vessel geometry. However, as discussed above, to achieve this kind of data density, it requires an additional vessel source, which is expensive.

[0011] Thus, there is a need for economically conducting a marine seismic survey using a flexible seismic source system that can be configured to meet different geophysical and operational objectives.

SUMMARY

[0012] According to one embodiment, there is a marine seismic acquisition system that includes a vessel towing an impulsive source array, wherein the impulsive source array includes air guns; a vibratory source array including plural vibratory source elements; plural seismic receivers configured to receive and record seismic energy emitted by the impulsive source array and the vibratory source array; and a controller configured to steer a beam of energy formed by the plural vibratory source elements. The controller drives the plural vibratory source elements to steer the beam of energy to illuminate an area of interest over which the impulsive source array is prohibited to pass.

[0013] According to still another embodiment, there is a method for acquiring marine seismic data that includes towing with a vessel an impulsive source array, wherein the impulsive source array includes air guns; firing the impulsive source array; firing a vibratory source array including plural vibratory source elements;

recording, with the plural seismic receivers, the seismic data generated by the firing of the impulsive source array and the vibratory source array; and steering with a controller a beam of energy formed by the plural vibratory source elements. The controller drives the plural vibratory source elements to steer the beam of energy to illuminate an area of interest over which the impulsive source array is prohibited to pass.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:

[0015] Figure 1 is a schematic diagram of a conventional marine seismic survey system;

[0016] Figure 2 is an overall view of an impulsive source sub-array having plural air guns connected to a float;

[0017] Figures 3A and 3B illustrate the coverage area during a seismic survey system when an obstacle is present;

[0018] Figure 4 illustrates a marine seismic acquisition system that uses an impulsive source array and a vibratory source array when an obstacle is present;

[0019] Figure 5 illustrates a distribution of the source elements of a vibratory source array when an obstacle is present;

[0020] Figures 6A and 6B illustrate a vibratory source geometry;

[0021] Figure 7 illustrates various receiver platforms that may be used for recording the seismic data with a vibratory source array;

[0022] Figures 8A to 8C illustrate a seismic survey in which a vibratory source array changes its geometry as a vessel tows streamers or as a swarm of

autonomous underwater vehicles passes by; [0023] Figures 9A to 9C illustrate another seismic survey using ocean bottom nodes or receivers distributed in the well as recording system in which a vibratory source array changes its geometry with the targeted frequency bandwidth of signal and offset;

[0024] Figure 10 shows a distribution of vibratory source elements in a vibratory source array;

[0025] Figure 1 1 illustrates the locations of various controllers that change a geometry of a vibratory source array;

[0026] Figure 12 is a flowchart of a method for acquiring seismic data with an impulsive source array and a vibratory source array; and

[0027] Figure 13 is a schematic diagram of a controller.

DETAILED DESCRIPTION

[0028] The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of a marine seismic acquisition system that uses at least one impulsive source array towed by a vessel and a vibratory source array that is independent of the impulsive source array. However, the embodiments to be discussed next are not limited to one impulsive source array and one vibratory source array, but may be applied to other combination or number of seismic source arrays.

[0029] Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0030] According to an embodiment, there is a marine seismic acquisition system 400 that includes a vessel 402 that tows an impulsive source array 404 and at least a streamer 410. The source array 404 includes impulsive source elements 406, e.g., air-guns, suspended from a float 408. Float 408 may float at the water surface 420, or under the water surface, as illustrated in the figure. Vessel 402 may tow more than one streamer. Each streamer 410 includes plural receivers 412 (only one shown for simplicity). In one embodiment, the vessel tows only the impulsive source array and the receivers are carried by other means, as will be discussed later.

[0031] It is noted that seismic energy 422 generated by the impulsive source array 404, after entering through the water bottom 424, partially gets reflected from the area of interest 426 (e.g., oil reservoir), and the reflected energy 428 is then recorded by receivers 412.

[0032] A vibratory source array 430 is located close to an obstacle 450, e.g., a drilling facility. Vibratory source array 430 may include three or more individual vibratory source elements 432 (see, for example, vibratory source element disclosed in U.S. Patent no. 8,837,259, the entire content of which is incorporated herein by reference). Each source element 432 may be suspended from a corresponding carrier 434, which may be a float, motorized float, unmanned vessel, underwater autonomous vessel, submarine, underwater vehicle, etc. In one embodiment, carriers 434 of the vibratory source elements 432 are independent of each other, i.e., they can move in the water surface plane and/or along gravity, independent of each other. In this way, a configuration of the vibratory source array may be modified during the seismic survey as will be discussed later. Also, this implementation of the vibratory source array allows the operator of the seismic survey to place the vibratory source elements around or next to the obstacle such that acoustic energy 436 emitted by these elements 432 also illuminate the area of interest 426 and the reflected energy 438 is recorded by the receivers 412.

[0033] The vibratory source elements 432 may be controlled by a controller 440, shown in this embodiment located on one carrier 434 (in another embodiment, controller 440 is located on vessel 402), as described, for example, in U.S. Patent Applications Serial No., 14/168,207 and 14/889,194 (the entire content of which is incorporated herein by reference). This means that a beam generated by the vibratory source array 430 is steerable to a desire location along the area of interest 426. The beam of energy emitted by the vibratory source array 430 may be controlled (its angle relative to the gravity) to sweep the area of interest 426 while the streamer 410 is passing by, so that the reflected energy 438 reaches receivers 412 located on the streamer or other platform. In other words, the vibratory source array may steer the beam of energy so that this beam follows the streamer's motion. In this way, this configuration enriches the seismic data collected by the receivers due to the impulsive source array 404, and also improves an illumination of the area of interest (e.g., reservoir production) where there is a lack of conventional seismic data as illustrated in Figure 3A. In one application, the configuration shown in Figure 4 optimizes the overall acquisition duration by replacing a conventional undershoot program, which is illustrated in Figure 3B. [0034] The geometry and location of the vibratory source elements 432 may be adjusted as a function of the shooting acquisition planning of the streamer vessel. For example, as illustrated in Figure 5, each element 432-1 to 432-5 of the marine vibratory source array 430 can be distributed along a line 560, around the

obstruction 450. Line 560 may be a semi-circle, or it may take other shapes, e.g., full circle, parabola, hyperbola, square, rectangle, etc. Not only the shape of line 540 may be controlled with controller 440, but also a distance "d" between each vibratory source element 432-i and the obstacle 450. If line 560 is a part of a circle, then distance d becomes the radius "r" of the circle, and the radius r can be adjusted as the vessel 402 or receivers 412 move relative to the vibratory source array 430. If line 560 is a full circle, then the energy of the source array can be controlled in all directions, e.g., azimuth and elevation. Other geometries may be used that include square, ellipse, pentagon, hexagon, etc. The number of individual vibratory source elements 432-i that are part of the source array 430 can vary between 3 and 100, with a more preferred number of about 4 to 16. Note that in this embodiment, although the source elements 432-i may change their location, a center point CS of the source array is fixed relative to obstacle 450. The center point CS of the source array may be defined as the center of symmetry of the source array, or the center of mass of the source array or by other known methods.

[0035] The elements 432-i of the vibratory source array 430 can be also distributed in space as a function of the depth D of reservoir (signal penetration), the targeted frequency bandwidth and the beam directivity, to optimize the efficiency of the reservoir illumination. For example, with regard to Figures 6A and 6B, a vibratory source array 630 includes plural vibratory source elements 632-i distributed along line 660. Line 660 is shown in the figure as being a circle. Figure 6A is a top view of the vibratory source array 630.

[0036] For this embodiment, the radius r of the vibratory source array 630 may be about 5 to 25 m for a high-frequency (HF) bandwidth of signal, i.e., a depth H1 of the source array at about 3-50 m relative to the water surface, and the radius may be changed to a value of about 10 to 50 m for a low-frequency (LF) bandwidth of signal, i.e., a depth H2 of the source array of about 10 to 100 m. In other words, as illustrated in Figure 6B, a radius r1 of the vibratory source array 630 and a depth H1 relative to the water source 620 (where the depth is measured to the center point CS having a location (x, y) of the source array) may be used for HF acquisition and a radius r2, different from r1 , and a depth H2, different from H1 , may be used for the LF acquisition. More than two depths and two radiuses may be used for seismic data acquisition. The source array 630 may be changed between the HF and LF acquisitions as needed (i.e., dynamically as the vessel is passing by), by controller 440 or a controller located on the passing vessel 402 (not shown in Figures 6A and 6B).

[0037] Note that Figure 6B shows the same source array 630 in two

configurations, the HF and LF configurations. However, in another embodiment, the vibratory source elements 632-i may be distributed at the same time, at both the HF and LF configurations and they may be activated at different times as the receivers closer or farther from the vibratory source array. In other words, while Figure 6B shows the same source array 630 first at a HF configuration and then moved at a LF configuration, the source array 630 may be configured from the beginning to have source elements at both depths H1 and H2 and activate them according to the need. Those skilled in the art would understand that more than two configurations are possible, and these configurations may not necessary be related to the frequency emitted by the energy, but they may be related to the offset relative to the receivers, etc.

[0038] Figure 7 shows the source array 730 having a given configuration (i.e., r and H) and being located next to obstacle 750. Note that in one application, the obstacle 750 may be located inside line 760 on which the vibratory source elements are distributed. In this embodiment, the seismic receivers 712 may be distributed not only on streamers 710, but also on other carriers, for example autonomous underwater vehicles 712A, ocean bottom nodes 712B, or even located on the well 752, as sensors 712C. In one application, only one of these carriers may be used to host the seismic receives. In another application, a combination of two or more of these carriers may be used for hosting the seismic receivers.

[0039] An embodiment in which the geometry and depth of the vibratory source array is changed as the receivers are passing the obstacle is illustrated in Figures 8A and 8B. The term "geometry" is understood herein to include (1 ) a distance of each of the plural vibratory source elements to a center point of the vibratory source array and/or (2) a distance of each of the plural vibratory source elements, or the center point of the source array, relative to the obstacle. Figure 8A show an HF configuration, in which the source array 830-HF has a radius r1 and depth H1 and the streamer 810 and/or AUVs 812A move past obstacle 850. As the vessel 802 is farther away from obstacle 850, as illustrated in Figure 8B (D2 > D1 ), the source array 830 is instructed to sink to a larger depth H2 > H1 , and have a higher radius r2 > r1 , to achieve a LF configuration 830-LF. Figure 8C shows both configurations 830-HF and 830-LF oriented along a same vertical axis V. Note, that for a static source array, vertical axis V, which includes the center point CS of the source array, having coordinates (x,y) in Figure 8C, is fixed, i.e., the center point CS of the source array can change its z (vertical) coordinate, but not the x and y coordinates. For a dynamic source array, the coordinates of the center point CS of source array can change in the horizontal plane, from the HF configuration to the LF configuration. In other words, the center point CS of the source array can move to optimize the illumination of the reservoir 826, to compensate for the movement of the seismic receivers. Figures 8A and 8B also shows that an angle γ between the vertical V and the energy emitted by the vibratory source array increases as the vessel moves away from the obstacle, which means that the beam of energy is controlled to follow the moving receivers.

[0040] The embodiments discussed above with regard to Figures 8A and 8B show the seismic receivers moving with their carrier, i.e., streamers or AUVs.

However, it is possible to use carriers that are stationary, i.e., ocean bottom nodes 912C or well receivers 912D as illustrated in Figures 9A to 9C. Source 930 is located close to obstacle 950 and angle γ between the vertical V and the energy emitted by the vibratory source array 930 is shown changing, which means that the controller controls the beam of energy to sweep the reservoir 926. Figures 9A and 9B show the ocean bottom nodes 912C located on the ocean bottom 924 and the well receivers 912D distributed along the length of the well 952. Figure 9C shows the HF configuration 930-HF having characteristics r1 and H1 and the LF

configuration 930-LF, having characteristics r2 and H2, larger than r1 and H1 , respectively. As for the previous embodiments, it is possible that vibratory source array 930 includes at the same time the configuration 930-HF and the configuration 930-LF and activates them at different times. In one application, more than two configurations of source elements may be included in the same source array. [0041] The embodiments discussed above have illustrated the vibratory source arrays to include plural vibratory source elements distributed in the same horizontal plane (substantially parallel to the water surface). However, it is possible to have the vibratory source elements distributed with different depths, as illustrated in Figure 10. For example, the vibratory source array 1030 may have plural branches 1031 -A to 1031 -B (only two are illustrated for simplicity, but the vibratory source array may include more than two branches), each branch having a curved shape. In this example, branches 1031 -A and 1031 -B have the shape of a parabola, which means that each source element 1032-i has a different depth Hi. In another embodiment, it is possible to have the branches follow a circle or ellipse or hyperbola, or a straight line that makes an angle with the horizontal instead of a parabola. Irrespective of the geometry adopted for this vibratory source array, the emitted beam of energy 1070 follows a direction 1072 that can make various angles with the vertical V, i.e., the beam direction is controlled.

[0042] The vibratory source arrays discussed in the previous embodiments have the vibratory source elements capable of moving independently relative to each other, for example, to increase the radius r or depth H. This can be achieved, for example, if each source element has its own carrier that is able to move to a desired position, as instructed by a global and/or local controller. For example, as illustrated in Figure 1 1 , it is possible that a global controller 1 140 is located on one of the carriers 1 134-i, and all the other carriers (see, for example, 1 134-1 ) have a corresponding local controller (see, for example, 1 135-1 ). The global controller 1 140 coordinates the local controllers 1 135-1 for achieving the desired geometry for the vibratory source array. In one embodiment, it is possible to have a controller 1 151 located on the obstacle and this controller acts as the global controller. In still another embodiment, a controller 1 103 of the vessel acts as the global controller and instructs the local controllers 1 135-1 to move the carriers at the desired locations.

[0043] For all these embodiments, the carrier 1 134-i of the vibratory source element is assumed to have actuation capabilities, i.e., one or more mechanisms for moving in the xy plane and desirably, a mechanism for changing the depth of the source element. Those skilled in the art would understand that other support structures for the source elements may be envisioned, for example, a rigid system of tubes, supported by a surface vessel, to which the vibratory source elements are attached. This system of tubes may have one or more horizontal stages for accommodating vibratory source elements at different depths and the entire system may be lowered or raised relative to the vessel.

[0044] A marine seismic acquisition system, as discussed in any of the above embodiments, may include a vessel towing an impulsive source array and plural seismic receivers, wherein the impulsive source array includes air guns. The system may also include a vibratory source array including plural vibratory source elements and a controller configured to steer a beam of energy formed by the plural vibratory source elements. The controller drives the plural vibratory source elements to steer the beam of energy to illuminate an area of interest, over which the impulsive source array and the plural receivers are prohibited to pass (for example, due to the presence of the obstacle).

[0045] In one application, the plural vibratory source elements are distributed along a line that takes a shape of an arc of a circle. In another application, the plural vibratory source elements are distributed along a line that takes a shape of a parabola, or ellipse, or hyperbola. The plural vibratory source elements are attached to corresponding carriers, each carrier being independent of the other carriers. The carriers are unmanned vessels or autonomous underwater vehicles.

[0046] The controller is configured to change a geometry of the vibratory source array. The geometry may include a distance of the plural vibratory source elements from a center point of the vibratory source array, or a depth of the plural vibratory source elements relative to the water surface, or (1 ) a distance of the plural vibratory source elements from a center point of the vibratory source array and (2) a depth of the plural vibratory source elements relative to the water surface.

[0047] The controller may be further configured to change a radius and/or depth of the plural vibratory source elements relative to a center point of the vibratory source array based on a distance of the plural receivers relative to the vibratory source array. In one application, the plural vibratory source elements are grouped in branches, and at least one branch has a non-linear shape.

[0048] According to an embodiment illustrated in Figure 12, there is a method 1200 for acquiring marine seismic data. The method includes a step 1202 of towing with a vessel an impulsive source array, wherein the impulsive source array includes air guns, a step 1204 of firing the impulsive source array, a step 1206 of firing a vibratory source array including plural vibratory source elements, a step 1208 of recording, with the plural seismic receivers, the seismic data generated by the firing of the impulsive source array and the vibratory source array, and a step 1210 of steering with a controller a beam of energy formed by the plural vibratory source elements. The controller drives the plural vibratory source elements to steer the beam of energy to illuminate an area of interest over which the impulsive source array is prohibited to pass. [0049] The plural vibratory source elements may be distributed along a line that takes a shape of an arc of a circle. In one application, the plural vibratory source elements are distributed along a line that takes a shape of a parabola, or ellipse, or hyperbola. The plural vibratory source elements are attached to corresponding carriers, each carrier being independent of the other carriers. The method may further include a step of changing a geometry of the vibratory source array.

[0050] Various controllers have been discussed above. Such controllers may be implemented as illustrated in Figure 13. Computing device 1300 includes a processor 1302 that is connected through a bus 1304 to a storage device 1306.

Computing device 1300 may also include an input/output interface 1308 through which data can be exchanged with the processor and/or storage device. For example, a keyboard, mouse or other device may be connected to the input/output interface 1308 to send commands to the processor and/or to collect data stored in the storage device or to provide data necessary to the processor. Alternatively, input/output interface 1308 may communicate with a transceiver for receiving positions of other controllers. The processor may be used to process, for example, position data, shooting data, etc. Results of this or another algorithm may be visualized on a screen 1310, which is attached to controller 1300.

[0051] The disclosed embodiments provide a system and a method for acquiring marine seismic data in the presence of obstacles. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a

comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.

[0052] Although the features and elements of the present exemplary

embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.

[0053] This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.

Claims

WHAT IS CLAIMED IS:

1 . A marine seismic acquisition system (400) comprising:

a vessel (402) towing an impulsive source array (404), wherein the impulsive source array (404) includes air guns;

a vibratory source array (430) including plural vibratory source elements

(432);

plural seismic receivers (412) configured to receive and record seismic energy emitted by the impulsive source array and the vibratory source array; and

a controller (440) configured to steer a beam of energy formed by the plural vibratory source elements (432),

wherein the controller (440) drives the plural vibratory source elements (432) to steer the beam of energy to illuminate an area of interest (426) over which the impulsive source array (404) is prohibited to pass.

2. The system of Claim 1 , wherein the plural vibratory source elements are distributed along a line that takes a shape of an arc of a circle.

3. The system of Claim 1 , wherein the plural vibratory source elements are distributed along a line that takes a shape of a parabola, ellipse, or hyperbola.

4. The system of Claim 1 , wherein the plural vibratory source elements are attached to corresponding carriers, each carrier being independent of the other carriers.

5. The system of Claim 4, wherein the carriers are unmanned vessels.

6. The system of Claim 4, wherein the carriers are autonomous underwater vehicles.

7. The system of Claim 1 , wherein the controller is configured to change a geometry of the vibratory source array.

8. The system of Claim 7, wherein the geometry includes a distance of each of the plural vibratory source elements to a center point of the vibratory source array.

9. The system of Claim 7, wherein the geometry includes a distance of each of the plural vibratory source elements relative to an obstacle.

10. The system of Claim 7, wherein the geometry includes (1 ) a distance of each of the plural vibratory source elements to a center point of the vibratory source array and (2) a distance of each of the plural vibratory source elements relative to an obstacle.

1 1 . The system of Claim 1 , wherein the controller is configured to change a radius and/or depth of the plural vibratory source elements relative to a center point of the vibratory source array, based on a distance of the plural receivers relative to the vibratory source array.

12. The system of Claim 1 , wherein the plural vibratory source elements are grouped in branches, and at least one branch has a non-linear shape.

13. The system of Claim 1 , wherein the plural seismic receivers are located on streamers.

14. The system of Claim 1 , wherein the plural seismic receivers are located on autonomous underwater vehicles.

15. The system of Claim 1 , wherein the plural seismic receivers are located on ocean bottom nodes.

16. A method for acquiring marine seismic data, the method comprising:

towing (1202) with a vessel (402) an impulsive source array (404), wherein the impulsive source array (404) includes air guns;

firing (1204) the impulsive source array; firing (1206) a vibratory source array (430) including plural vibratory source elements (432);

recording (1208), with the plural seismic receivers, the seismic data generated by the firing of the impulsive source array and the vibratory source array; and

steering (1210) with a controller (440) a beam of energy formed by the plural vibratory source elements (432),

17. The method of Claim 16, wherein the plural vibratory source elements are distributed along a line that has a shape of an arc of a circle.

18. The method of Claim 16, wherein the plural vibratory source elements are distributed along a line that takes a shape of a parabola, or ellipse, or hyperbola.

19. The method of Claim 16, wherein the plural vibratory source elements are attached to corresponding carriers, each carrier being independent of the other carriers.

20. The method of Claim 16, further comprising:

changing a geometry of the vibratory source array.