BR102017026815B1 - METHOD AND ARRANGEMENT FOR A MARINE SEISMIC SURVEY - Google Patents

Abstract

CROSS LINE SOURCE SEPARATION BASED ON CROSS LINE STREAMER SEPARATION. The present invention relates to a method for a marine seismic survey which may include towing streamers that are spaced apart in a transverse line direction by a streamer separation (L) and towing seismic source elements that are spaced apart in a transverse line direction. by a source separation based on an integer (k), an inverse of a quantity of the seismic source elements (1/S), and the streamer separation as represented by (k+1/S)L. Seismic source elements may be actuated and seismic signals may be detected at each of a plurality of receivers on the streamers.

Description

CROSS REFERENCE TO RELATED ORDERS

[0001] This application claims priority to US Provisional Application 62/434,244, filed on December 14, 2016, which is incorporated herein by reference.

BASIS

[0002] In the past few decades, the petroleum industry has invested heavily in the development of marine seismic survey techniques that generate knowledge of underground formations beneath a body of water in order to find and extract valuable mineral resources, such as oil. High-resolution images of an underground formation are useful for quantitative interpretation and improved reservoir monitoring. During a typical marine seismic survey, a marine survey vessel tows one or more sources below the water's surface and over an underground formation to be surveyed for mineral deposits. The receivers may be located on or near the seabed, on one or more streamers towed by the marine research vessel, or on one or more streamers towed by another vessel. The marine research vessel typically contains marine research equipment, such as navigation control, source control, receiver control, and recording equipment. Source control can cause one or more sources, which may be air guns, marine vibrators, electromagnetic sources, etc., to produce signals at selected times. Each signal is essentially a wave called a wave field that travels downward through the water and into the underground formation. At each interface between different rock types, a portion of the wave field may be retracted, and another portion may be reflected, which may include some scattering, back into the water body to propagate toward the water surface. The receivers, in this way, measure a wave field that was initiated by the action of the source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Figure 1 illustrates a front or back view (xz plane) of marine seismic survey in which acoustic signals are emitted by a source to record receivers.

[0004] Figure 2 illustrates a plan view (yx plane) of marine seismic survey with two seismic source elements positioned outside the two internal streamers.

[0005] Figure 3 illustrates a front or back view (yz plane) of a previous configuration of an arrangement of seismic source elements and streamers where two seismic source elements are positioned between the two inner streamers.

[0006] Figure 4 illustrates a front or back view (yz plane) of a configuration of an arrangement of seismic source elements and streamers where two seismic source elements are positioned outside the two inner streamers.

[0007] Figure 5 illustrates a front or back view (yz plane) of a configuration of an arrangement of seismic source elements and streamers where two seismic source elements are positioned outside the two inner streamers.

[0008] Figure 6 illustrates a front or back view (yz plane) of a configuration of an arrangement of seismic source elements and streamers where two seismic source elements are positioned outside the two inner streamers.

[0009] Figure 7 illustrates a front or back view (yz plane) of an arrangement of seismic source elements and streamers where two seismic source elements are positioned outside the four inner streamers.

[00010] Figure 8 illustrates a front or back view (yz plane) of a configuration of an arrangement of seismic source elements and streamers where two seismic source elements are positioned outside the four inner streamers.

[00011] Figure 9 illustrates a front or back view (yz plane) of a configuration of an arrangement of seismic source elements and streamers where two seismic source elements are positioned outside the four inner streamers.

[00012] Figure 10 illustrates a plan view (yx plane) of marine seismic survey with two of three seismic source elements positioned outside the two inner streamers.

[00013] Figure 11 illustrates a front or back view (yz plane) of a previous configuration of an arrangement of seismic source elements and streamers where three seismic source elements are positioned between the two inner streamers.

[00014] Figure 12 illustrates a front or back view (yz plane) of a configuration of an arrangement of seismic source elements and streamers where two of three seismic source elements are positioned outside the two inner streamers.

[00015] Figure 13A illustrates a front or back view (yz plane) of a configuration of an arrangement of seismic source elements and streamers where two seismic source elements are positioned outside the four inner streamers.

[00016] Figure 13B illustrates a plan view (yx plane) of sublines for consecutive actuations of seismic source elements associated with a configuration of an arrangement of seismic source elements and streamers for a navigation line.

[00017] Figure 14 illustrates a plan view (yz plane) of sublines for two adjacent navigation lines where the separation of navigation line from transverse line is such that there is no overlap of the sublines.

[00018] Figure 15A illustrates a plan view (yz plane) of sublines for two adjacent navigation lines where the separation of navigation line from transverse line is such that there is overlap of the sublines.

[00019] Figure 15B illustrates a plan view (yz plane) of sublines for two adjacent navigation lines where the separation of navigation line from transverse line is such that there is overlap of the sublines.

[00020] Figure 16 illustrates a method for a marine seismic survey.

[00021] Figure 17 illustrates a method for a marine seismic survey.

DETAILED DESCRIPTION

[00022] This disclosure generally relates to the field of marine research. Marine research may include, for example, seismic research, among others. For example, this disclosure may have applications in marine seismic research, in which one or more sources are used to generate wave fields, and receivers (towed and/or ocean floor) receive energy generated by the sources and affected by interaction with a subsurface formation. The receivers, in this way, collect marine seismic survey data, which can be useful in the discovery and/or extraction of hydrocarbons from subsurface formations.

[00023] Marine seismic surveys can cover a large area; for example, hundreds or thousands of square kilometers of seabed. However, only a portion of the area can be searched at one time. A marine seismic survey may be performed with a marine survey vessel towing an array of seismic source elements and one or more streamers, which may limit subline coverage to a shipping line. As used herein, "underline" refers to a line of receiver-source midpoints in the in-line direction for a particular seismic source element and all receivers in a particular streamer. As used herein, "receiver-source midpoint" refers to a planar surface coordinate in the xy-plane that is midway between the location of a particular seismic source element and the location of a particular receiver where it occurs. the reflection of a wave field. The planar surface coordinate can be expressed as (x,y). The x-coordinate can correspond to an in-line position and the y-coordinate can correspond to a cross-line position. As used herein, "in line" refers to the ship's direction of travel, and "transverse line" is perpendicular to the ship's direction of travel. For reasons of efficiency, illustrations and subline descriptions in this document are drawn assuming that all streamers in an array are straight and parallel. However, sublines can be curved when pennants are curved such as in a spiral navigation line. As used herein, "doubling" refers to the number of times there are contributions to a subline from any combination of seismic source and receiver element. As used herein, "subline coverage" refers to the distance between the two outer sublines. As a result of limits on subline coverage, it can take several days to several months to complete a marine seismic survey. The size of the area that can be surveyed at once may depend on the configuration of the arrangement of streamers and seismic source elements. For example, as the marine seismic survey vessel tows the arrangement of streamers and seismic source elements in a particular configuration, the spacing of the cross-line streamer and the cross-line separation may determine the width of a subline cover. researched by the configuration of streamers and seismic source elements. Crossline subline coverage is generally smaller than the streamer diffusion width. As used herein, "streamer spread width" refers to the transverse line distance between the outer streamers of a streamer array.

[00024] A marine seismic survey may include a single navigation line, such as a spiral navigation line, or multiple navigation lines to survey a survey area. As transverse line source separation increases, subline coverage increases for a corresponding navigation line. Thus, it may be beneficial to increase transverse line source separation to increase subline coverage so that a larger portion of an area can be searched at once and the total search completion time can be reduced by using fewer lines. navigation. As the width of each pass increases, a larger portion of the search area can be searched at once. Therefore, fewer navigation lines may be required to complete the marine seismic survey. As a result, marine seismic survey can be completed in less time.

[00025] Increasing transverse line source separation can improve subsurface sampling. Increasing the transverse line source separation can give short near deviations for a large portion of streamers. The number of receivers with short near offsets can be increased by increasing the transverse line source separation. As used herein, "offset" refers to the distance between a seismic source element and any receiver on a streamer. In contrast, "near offset" for a particular streamer refers to the distance between a seismic source element and the receiver that is located closest to the seismic source element. In processing, marine seismic survey data, such as reflection information, only from receivers with short near offsets can contribute to subsurface imaging. When a seismic source element and a receiver are located closely together, the ray path from the seismic source element to the subsurface and back to the receiver is generally vertical. In contrast, the ray path through the subsurface is generally at a high angle when the offset is long. The physics of elastic solids is such that the amplitude of a reflected wave field varies with the offset for reflections from the same interface, even when the material properties on either side of the interface are the same at each reflection. Reflection information from reflections at nearby offsets can be used to infer properties and composition of the subsurface and to examine reflection amplitudes at other offsets. Near-offset reflection information, such as amplitude, can be used in Amplitude versus Offset (AVO) analysis to infer subsurface composition. When processing reflection information for shallow geology, only reflection information corresponding to shorter offsets can be used. Thus, if the nearby offsets are large such that the streamers are a long distance behind seismic source elements or some of the streamers are far from the seismic source elements in the transverse line direction then there may be reflection information that contributes for shallow seismic imaging. A three-dimensional seismic volume may then contain weak shallow reflection types of information at the boundaries between adjacent navigation lines. The resolution of a subsurface image at navigation line boundaries can be improved by increasing transverse line source separation.

[00026] Short near offsets can help predict multiples in marine seismic survey data by increasing the number of receivers with short near offsets relative to some previous approaches. With a wider transverse line source separation, the near offset for streamers near the center of a streamer array and the edges of the streamer array may be short. The predicted multiples can be subtracted from marine survey seismic data otherwise known to one of skill in the art. As used herein, "multiple" refers to wave fields that have undergone more than one reflection. For example, a manifold may be a wave field that reflects off the sea floor, such as a solid surface 104 illustrated in Figure 1, then reflects off the sea surface, such as the water surface 109, then reflects off the surface. subsurface, so that the first layer of rock is elevated 112, and is then received by one of the receivers 122. The high resolution of the reflection information from receivers with short near deviations improves the ability of multiple predictions.

[00027] It should be understood that the present disclosure is not limited to particular methods or devices, which may, in fact, vary. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an", and "the" include singular and plural referents unless the content clearly dictates otherwise. Furthermore, the word "may" is used throughout this order in a permissive sense (having the potential to, being able to), not in an obligatory sense (ought). The term "include," and derivations thereof, mean "including, but not limited to." The term "coupled" means directly or indirectly connected.

[00028] The figures in this document follow a numbering convention in which the first digit or digits correspond to the number of the figure in the drawing and the remaining digits identify an element or component in the drawing. Similar components or elements between different figures can be identified by using similar digits. For example, 226 may reference the element "26" in figure 2, and a similar element may be referenced as 326 in figure 3. Analogous elements within a figure may be referenced with a hyphen and extra number or letter. See, for example, elements 320-1, . . . , 320-14 in figure 3. Such analogous elements can generally be referenced without the hyphen and extra number or letter. For example, elements 320-1, . . . , 320-14 may be collectively referred to as 320. As will be appreciated, elements shown in the various embodiments herein may be added, exchanged and/or deleted in order to provide a number of additional embodiments of the present disclosure. Furthermore, as will be appreciated, the proportion and relative scale of the elements provided in the figures are intended to illustrate certain embodiments of the present invention, and cannot be taken in a limiting sense.

[00029] Figure 1 illustrates a front or study view (xz plane 130) of marine seismic survey in which acoustic signals are emitted by a seismic source 126, such as a seismic source element, for recording by receivers 122 for processing and analysis in order to help characterize the structures and distributions of resources and materials underlying the earth's solid surface. Figure 1 shows a domain volume 102 of the earth's surface comprising a solid volume 106 of sediment and rock beneath the solid surface 104 of the earth which, in turn, underlies the fluid volume 108 of water having a water surface 109 such as in an ocean, an inlet or bay, or a large freshwater lake. The 102 domain volume shown in Figure 1 represents an exemplary experimental domain for a class of marine seismic surveys. Figure 1 illustrates a first sediment layer 110, a raised rock layer 112, second underlying rock layer 114, and saturated hydrocarbon layer 116. One or more solid volume elements 106, such as the first sediment layer 110 and the first layer of elevated rock 112, may be an overburden for the saturated hydrocarbon layer 116. In some cases, the overburden may include salt.

[00030] Figure 1 shows an example of a marine research vessel 118 equipped to carry out marine seismic research. In particular, the marine research vessel 118 may tow one or more streamers 120 (shown as a streamer for ease of illustration) generally located below the surface of the water 109. The streamers 120 may be long cables containing power and transmission lines. data (fiber optics, etc.) to which receivers can be connected. In one type of marine seismic survey, each receiver, such as receiver 122 represented by the shaded disk in Figure 1, comprises one or more sensors including a motion sensor that detects displacement of particles within the water by detecting variation in particle movement. , such as velocities or accelerations, and/or a hydrophone that detects changes in pressure. In another type of marine seismic survey, each receiver may include one or more hydrophones and two or more motion sensors. Streamers 120 and marine research vessel 118 may include sophisticated detection electronics and data processing facilities that allow receiver readings to be correlated with absolute positions on the water surface and absolute three-dimensional positions with respect to a coordinate system. three-dimensional. In Figure 1, the receivers along the streamers are shown to be below the surface of the water 109, with the receiver positions correlating with overlapping surface positions, such as a surface position 124 correlating with the receiver position 122. Marine research vessel 118 may also tow one or more seismic source elements 126 that produce acoustic signals as the marine research vessel 118 and streamers 120 move across the water surface 109. A seismic source element 126 it is a single seismic source just like a single air gun. The seismic source elements 126 may be grouped together and be the components of one or more seismic source subarrays. As used herein, "seismic source subarray" refers to seismic source elements that can be actuated separately or simultaneously. For example, seismic source elements of a seismic source subarray may be actuated separately and sequentially, but without any overlap in recording time between the actuations of the seismic source elements. Alternatively, the seismic source elements of a seismic source subarray may be actuated simultaneously with an overlap in recording time between the actuations of the seismic source elements. A seismic source subarray may be seismic source elements that are coupled to a common towline. A seismic source subarray may have a common feed line coupled to the seismic source elements of the seismic source subarray.

[00031] The streamers 120 may be spaced apart (away from an adjacent streamer) by a transverse line streamer separation. The direction of the transverse line is in the y direction (not illustrated in figure 1), which is inside and outside the page. Adjacent seismic source elements 126 may be spaced apart by a transverse line source separation. Crossline source separation may be greater than crossline streamer separation. Cross-line source separation can be based on cross-line streamer separation. Cross-line source separation and cross-line streamer separation are illustrated and discussed further below in association with Figures 2 through 16.

[00032] Seismic source elements 126 and/or streamers 120 may also be towed by other independent vessels, or may otherwise be disposed in fluid volume 108. For example, receivers may be located on cables or bottom nodes of the ocean fixed on or near the solid surface 104, and seismic source elements 126 may also be arranged in a fixed or near-fixed configuration. The streamers 120 may be towed by a marine research vessel 118, and the seismic source elements 126 may be towed by one or more independent vessels. For reasons of effectiveness, illustrations and descriptions in this document showing seismic receivers located on a "streamer" or "cable" should be read to refer equally to seismic receivers located on a towed streamer, an ocean floor receiver cable, and/or an arrangement of nodes.

[00033] Figure 1 shows an expanding, spherical acoustic signal illustrated as semicircles of increasing radius centered on the seismic source element 126, representing a downward wavefield 128, following an acoustic signal emitted by the seismic source element 126. The downward-going wavefield 128 is, in effect, shown in a vertical plane cross-section in Figure 1. The downward-going wavefield 128 expanding outward and inward may eventually reach the solid surface 104, on which point the downward-going wavefield 128 expanding outward and downward may partially diffuse, may partially reflect back to the streamers 120, and may partially retract downward into the solid volume 106, making the acoustic signals elastic within the solid volume 106.

[00034] One or more depth and lateral force (LFD) control devices (not shown in Figure 1) may be components of or coupled to streamers 120. Each LFD control device may include one or more rotating control surfaces that when moved to a selected rotary orientation with respect to the direction of movement of such surfaces through the fluid volume 108 creates a hydrodynamic lift in a selected direction to excite the streamer 120 in an up and down direction in the fluid volume 108 or sideways along the water surface 109 with respect to the direction of movement of the marine research vessel 118. Thus, LFD control devices can be used to maintain the streamers in a particular geometric arrangement. For example, the streamers 120 may be substantially straight and parallel to each other. LFD control devices can be used to induce a streamer diffusion angle. As used herein, "streamer diffusion angle" refers to an angle between a navigation line of the marine research vessel 118 and one of the streamers 120. Inducing a streamer diffusion angle that is greater than zero degrees may cause the crossline streamer separation at the forward end of the streamers 120 to be less than the crossline streamer separation at the rear end, or aft, end of the streamers 120. This gradual increase in streamer separation from transverse line from the front end to the rear end of the streamers 120 can "disperse" the streamers 120. By dispersing the streamers one can increase the uniformity of bending in the sublines near the edges of each navigation line, thereby reducing the probability Streamer plumage may cause distant ends of streamers not to contribute to all sublines. Streamer plumage can be caused by prevailing conditions such as currents.

[00035] Figure 2 illustrates a plan view (yx plane 232) of marine seismic survey with two seismic source elements 226-1 and 226-2. Figure 2 shows an example of a marine survey vessel 218, which may be analogous to the marine seismic survey vessel 118 illustrated in Figure 1, equipped to perform marine seismic surveys. The marine seismic survey vessel 218 may tow one or more streamers, such as streamers 220-1, 220-2, 220-3, and 2204, which may be analogous to the streamer 120 illustrated in Figure 1. The streamers 220- 1, 220-2, 220-3, and 220-4 may include one or more receivers (represented by small rectangles), such as receivers 222-1, 222-2, 222-3, and 222-4, which may be analogous to the receivers 122 illustrated in Figure 1. The streamers 220-1, 220-2, 220-3, and 220-4 are collectively referred to as the streamers 220, the receivers 222-1, 222-2, 222-3, and 222-4 and the unnumbered receivers in figure 2 are collectively referred to as the receivers 222, and the seismic source elements 226-1 and 226-2 are collectively referred to as the sources 226. The marine seismic survey vessel may tow a or more seismic source elements, such as seismic source elements 226-1 and 226-2, which may be analogous to the seismic source elements 126 illustrated in Figure 1. The recorded data may be three-dimensional in that it includes field data. wave traveling in both a line (x) direction and a transverse line (y) direction, more depth. Although Figure 2 illustrates two seismic source elements 226-1 and 226-2, four streamers 220, and thirty-two receivers 222, the embodiments are not so limited.

[00036] Marine research vessel 218 may include a control system and a recording system, which may be separate systems that communicate data between one another, or they may be subsystems of an integrated system. The control system may be configured to selectively actuate seismic source elements 226, while the recording system may be configured to record signals generated by receivers 222 in response to energy transmitted into the water and thereby into rock formations. underground material below the solid surface. The recording system can be configured to determine and record the geodetic positions of the seismic source elements and the receivers 222 at any time. The actuation of the seismic source element and the signal recording by the receivers 222 may be repeated a plurality of times as the marine research vessel 218 moves through the water. Each actuation register may include, for each of the receivers 222, signals corresponding to the energy produced by the seismic source elements 226.

[00037] Cross line pennant separation 231 illustrates the spacing of pennant 220-2 from pennant 220-3. The direction of the transverse line is in the y-direction illustrated in Figure 2. Although only indicated for streamers 220-2 and 220-3, streamer 220-1 can be spaced apart from streamer 220-2 by separating the streamer from transverse line 231 and the streamer 220-3 may be spaced from the streamer 220-4 by the transverse line pennant separation 231. The transverse line pennant separation 231 may be a nominal transverse line pennant separation. As used herein, a "nominal crossline streamer separation" refers to the crossline distance between the front ends of adjacent streamers. The cross-line pennant separation 231 may be a mid-cross-line pennant separation. When the streamers 220 are spaced irregularly apart from each other, the transverse line separation 231 may be the average of the transverse line separation between each of the streamers 220. For example, the transverse line pennant separation 231 may be the average of the spacing of the 220-1 pennant from the 220-2 pennant, the spacing of the 220-2 pennant from the 220-3 pennant, and the spacing of the 220-3 pennant from the 220-4 pennant. In at least one embodiment, the streamers 220 may be towed in a curved path.

[00038] As illustrated in Figure 2, the seismic source element 2261 is spaced from the seismic source element 226-2 by a transverse line source separation 250. In at least one embodiment, the transverse line source separation 250 may be directly proportional to the transverse line pennant separation 231, which is a distance identified as length (L). In at least one embodiment, the proportionality constant may be a more appropriate fraction than a total number as represented by the expression k + 1/S. In at least one embodiment, the transverse line source separation 250 may be based on an integer (k), an inverse of the quantity of the seismic source elements 226 (1/S), and the transverse line streamer separation 231 for a particular marine seismic survey. The transverse line source separation 250 may be based on a dome of the integer (k) and the inverse of the quantity of the seismic source elements (1/S) multiplied by the transverse line streamer separation (L) as represented by the expression (k + 1/S)L. As an example, when the crossline source separation 250 is an odd or even multiple of the crossline streamer separation 231 plus one-half of the crossline streamer separation 231, the crossline subline separation is one-quarter of the cross line streamer separation 231. In at least one embodiment, the integer (k) may be between one and one less than a streamer quantity (N-1), inclusive. As in the example in Figure 2 where there are four streamers 220, the integer number (k) can be 1, 2 or 3. In at least one embodiment, the integer (k) can be between one and half the number of streamers (N /2), inclusive. As in the example of Figure 2 where there are four streamers 220, the integer (k) can be 1 or 2. In at least one embodiment, the integer (k) can be between one and half of a smaller than the quantity of the streamers. pennants ((N- 1)/2), inclusive. As in the example in figure 2 where there are four streamers 220, the integer (k) can be 1 or 2. For example, if N is 8, then the range of the integer (k) is linked by 1 and 7/2 ( 3.5). The integer (k) may be 1, 2, or 3. In at least one embodiment, the transverse line source separation 250 may be based on an integer (k), a multiple (a) of an inverse of the quantity of the seismic source elements 226 (a/S), and the transverse line pennant separation 231 for a particular marine seismic survey. Additional examples of various transverse line source separations based on various values of the integer (k), various transverse line streamer separations, and various amounts of seismic source elements are discussed further below in association with Figures 3 through 13A. .

[00039] In at least one embodiment, the cross-line source separation 250 may be based on an integer (ke) and the cross-line streamer separation (L) 231. The cross-line source separation 250 may be based on even integer multiplication (ke) and cross line pennant separation (L) 231 as represented by the expression keL. The even integer (ke) ensures that the seismic source elements 226 are nominally positioned between a pair of adjacent streamers as opposed to being positioned in line with a streamer. As used herein, "nominally positioned between a pair of adjacent streamers" refers to situations where external factors, such as waves and turbulence caused by one or more ships, temporarily cause a seismic source element to not be positioned between a pair of adjacent streamers. In some prior approaches, seismic source elements can be positioned in line with a streamer when the transverse line source separation is based on multiplying an odd integer and the transverse line pennant separation. If a seismic source element, such as the 226-1 seismic source element, was in line with a streamer, such as the 220-2 streamer, then there may be physical interference with the respective connections of the 226-1 seismic source element. and pennant 220-2, signal interference in the form of noise in marine seismic survey data, or both physical and signal interference. Positioning a seismic source element between a pair of streamers can improve transverse line spatial resolution relative to that when a seismic source element is positioned in line with a streamer. Figures 5 and 8 illustrate example configurations of an array of seismic source elements and streamers where the transverse line source separation is based on the multiplication of an odd integer (ke) and the transverse line streamer separation (L). .

[00040] For reasons of efficiency, illustrations and descriptions in this document include individual seismic source elements. However, in at least one embodiment the transverse line source separation 250 may be the distance between an adjacent subarray of seismic sources. As used herein, a "seismic source subarray" refers to a plurality of seismic source elements. For example, a first seismic source subarray may be positioned where the seismic source element 226-1 is positioned in Figure 2 and a second seismic source subarray may be positioned where the seismic source element 226-2. If the seismic source elements of a seismic source subarray are actuated together then the location of the seismic source subarray can be grouped together and represented by a single point at the geometric center of the seismic source subarray. The transverse line source separation 250 may then be the distance between the geometric centers of the first and second seismic source subarrays. In contrast, if the seismic source elements of a seismic source subarray are actuated individually then the transverse line source separation 250 may be the distance between corresponding seismic source elements of the first and second seismic source subarrays. . The first seismic source subarray may include the same amount or a different amount of seismic source elements as the second seismic source subarray. The transverse line source separation 250 may be based on a sum of the integer (k) and the inverse of the seismic source subarray quantity (1/SA) multiplied by the transverse line streamer separation (L) as depicted by the expression (k + 1/SA)L.

[00041] As discussed above, a benefit of increasing transverse line source separation may be shorter near deviations over a large portion of the streamers. A wider transverse line source separation may yield shorter near offsets to the outer streamers in a streamer array than for a narrower source separation. For example, in Figure 2, the near offset for the seismic source element 226-1 and the streamer 2201 is the distance from the seismic source element 226-1 and the receiver 222-1. The near offset for the seismic source element 226-1 and the streamer 220-2 is the distance from the seismic source element 226-1 and the receiver 222-2. Figure 2 illustrates the seismic source elements 226 being positioned outside the streamers 220. However, the seismic source elements 226 may be positioned above the streamers 220 such that the seismic source elements 226 are aft of the front end of the streamers. 220. Therefore, the near deviation of a pennant cannot be the receiver located at the front end of the pennant. The seismic source elements 226 can be positioned above the streamers 220 by using longer lines for the seismic source elements 226 or by having the seismic source elements be towed by another ship.

[00042] With a wider transverse line source separation, the near offset for streamers near the center of the streamer array, such as streamers 220-2 and 220-3, and the near offset for streamers near the edges of the array of streamers, such as streamers 220-1 and 220-4, may be short. Short near offsets can help in predicting multiples in marine seismic survey data. The predicted multiples can be subtracted from marine survey seismic data. Subtraction of multiples from marine seismic survey data can be performed in any manner known to one of skill in the art.

[00043] Figure 3 illustrates a front or back view (yz plane 334) of a previous configuration of seismic source elements 326-1 and 326-2 and streamers 320-1, 320-2, 320-3, 320-4 , 320-5, 320-6, 320-7, 3208, 320-9, 320-10, 320-11, 320-12, 320-13, and 320-14 where two seismic source elements 326-1 and 326 -2 positioned between the two internal streamers 320-7 and 320-8. Each of the circles illustrated in Figures 3 to 9 and 11 to 13A represents a receiver, such as the receiver 122 illustrated in Figure 1, in each of the pennants. Figures 3 through 9 and 11 through 13A show fourteen streamers and two (or three) seismic source elements configured to be towed by a marine research vessel, such as the marine research vessel 218 illustrated in Figure 2.

[00044] In Figure 3, the transverse line source separation 351 between seismic source elements 326-1 and 326-2 is half of the transverse line streamer separation 331 (L/2). The direction of the transverse line is in the y direction illustrated in Figures 3-15B. Although the cross-line streamer separation 331 is shown to be between streamers 320-1 and 320-2, the cross-line streamer separation 331 may be the distance between any two adjacent streamers of streamers 320 or the average of the distances between the adjacent streamers of the streamers 320. This also applies to the transverse line streamer separation illustrated in Figures 4 through 9 and 11 through 13A. Although in Figures 3 through 9 and 11 through 13A the streamers and seismic source elements are illustrated to be on the surface of the water, the streamers, seismic source elements, or streamers and seismic source elements may be a depth below the surface of the water.

[00045] In figures 3 to 9 and 11 to 13A, ray paths are shown from each of the seismic source elements down the solid surface at a respective source-receiver midpoint back above one of the streamers. For example, the source-receiver midpoint 378 corresponds to the streamer 320-7 and the seismic source element 326-1 illustrated in Figure 3. A ray path may represent a trajectory from a point on an acoustic wavefront propagating from a seismic source element, to the subsurface and then back above a receiver. For example, from the seismic source element 326-1 to the solid surface 304 and then back above the streamer 320-7 illustrated in Figure 3. The nominal transverse line subline separation is a fraction of the line streamer separation transverse for a particular configuration of an arrangement of seismic source elements and streamers. For example, the nominal crossline subline separation 333 illustrated in Figure 3 is one-quarter of the crossline streamer separation 331 (L/4). As used herein, "nominal crossline subline separation" refers to a distance in the crossline direction between adjacent sublines that depends on the crossline pennant separation. A smaller nominal transverse line subline separation in the transverse line direction can increase the transverse line resolution of marine seismic survey data and an image generated from the marine seismic survey data. Subline coverage can be the distance between the external source-receiver midpoints. For example, subline coverage 340 shows the length of the subline coverage for the particular configuration illustrated in Figure 3. As discussed further below in association with Figures 13B through 15, a source-receiver midpoint has a fold subline corresponding complete. Thus, the nominal transverse line subline separation may be analogous to a transverse line subline separation between adjacent full ply sublines.

[00046] In the example of figure 3, the transverse line streamer separation 331 is 100 meters (m) so that the transverse line source separation 351 is 50 m. The seismic source element 326-1 is positioned 25 m to the right of the streamer 320-7 and the seismic source element 326-2 is positioned 25 m to the left of the streamer 320-8. The 333 nominal transverse line subline separation is 25 m. The coverage of Subline 340 is 675 m.

[00047] Figure 4 illustrates a front or back view (yz plane 434) of a configuration of seismic source elements 426-1 and 426-2 and streamers 420-1, 420-2, 420-3, 420-4, 420-5, 420-6, 420-7, 420-8, 420-9, 420-10, 420-11, 420-12, 420-13, and 420-14 where two seismic source elements 426-1 and 426-2 are positioned on the outside of the two inner pennants 420-7 and 420-8. In contrast to the example of Figure 3, the transverse line source separation 450 is greater than the transverse line source separation 351 so that seismic source elements 426-1 and 426-2 are positioned outside the streamers. 420-7 and 420-8. The cross-line source separation 450 may be analogous to the cross-line source separation 250 illustrated in Figure 2. In Figure 4, the cross-line source separation 450 is based on the cross-line streamer separation 431 (L).

[00048] The transverse line source separation 450 is based on the sum of the integer (k) and the inverse of the quantity of the seismic source elements (1/S) multiplied by the transverse line pennant separation 431 (L) as depicted by the expression (k + 1/S)L. As in the example in figure 3, the cross line pennant separation 431 is 100 m. In the example of Figure 4, the integer (k) is one and there are two seismic source elements 426. Thus, the transverse line source separation 450 is (1+1/2)*100 m, or 150 m. The seismic source element 426-1 is positioned 25 m to the left of the streamer 420-7 and the seismic source element 426-2 is positioned 25 m to the right of the streamer 420-8.

[00049] Even though the cross-line source separation 450 is wider than the cross-line source separation 351, the nominal cross-line subline separation 433 is still one-quarter of the cross-line streamer separation 431 (L /4), or 25 m, as in the example in figure 3, without having to increase the number of pennants (N) or decrease the transverse line pennant separation (L) 431. The subline coverage 441 is 725 m, 50 m larger than the subline cover 340 in the example of Figure 3. However, the subline cover 441 includes two fold sublines as indicated by the open vertical arrows.

[00050] The sublines and their corresponding coordinates can be described using a uniform rectangular grid independent of the geometry of the streamers. For example, if prevailing conditions cause the geometry of the streamers to be curved, the sublines are still described using the same uniform rectangular grid. Sublines can be spaced apart from each other by nominal crossline subline separation. However, for some crossline source separations, such as crossline source separation 450, there may be an irregularity in the crossline subline separations within a particular subline cover, such as subline cover 441. The irregularity in the crossline subline separations may be a different crossline subline separation than the nominal crossline subline separation for certain outer portions of the subline cover. Irregularity in transverse line subline separations can be represented by a "zero bend subline", which refers to a location where a finite bend subline (non-zero bend subline) can be if the transverse line subline separation nominal continued, but for irregularity in the transverse line subline separations. A zero-fold subline may correspond to downscaling marine seismic survey data or contributions to a subsurface image. Zero-fold sublines are discussed further below in association with Figures 13 to 15.

[00051] Figure 5 illustrates a front or back view (yz plane 534) of a configuration of seismic source elements 526-1 and 526-2 and streamers 520-1, 520-2, 520-3, 520-4, 520-5, 520-6, 520-7, 520-8, 520-9, 520-10, 520-11, 520-12, 520-13, and 520-14 where two seismic source elements 526-1 and 526-2 are on the outside of the two inner pennants 520-7 and 520-8. In contrast to the example of Figure 3, the transverse line source separation 552 is wider than the transverse line source separation 351 so that the seismic source elements 526-1 and 526-2 are positioned outside the streamers 5207 and 520-8. The cross-line source separation 552 may be analogous to the cross-line source separation 250 illustrated in Figure 2. In Figure 5, the cross-line source separation 552 is based on the cross-line streamer separation 531 (L).

[00052] Crossline source separation 552 is based on the even integer (ke) multiplied by crossline streamer separation 531 (L) as represented by the expression keL. As in the example in Figure 4, the cross line pennant separation 531 is 100 m. However, in contrast to the example in figure 4, in the example in figure 5 the even integer (ke) is two. Thus, the 552 transverse line source separation is 2*100 m, or 200 m. The seismic source element 526-1 is positioned 50 m to the left of the streamer 520-7 and the seismic source element 526-2 is positioned 50 m to the right of the streamer 520-8. The nominal 533 crossline subline separation is half the 531 crossline pennant separation (L/2), or 50 m. The subline coverage 543 is 750 m, 25 m larger than the subline coverage 441 in the example of Figure 4. The subline coverage 543 does not include zero-ply sublines, but it does include double-ply sublines, as indicated by the thick vertical arrows. Double fold sublines correspond to two coincident, or nearly coincident, source-receiver midpoints.

[00053] Figure 6 illustrates a front or back view (yz plane 634) of a configuration of seismic source elements 626-1 and 626-2 and streamers 620-1, 620-2, 620-3, 620-4, 620-5, 620-6, 620-7, 620-8, 620-9, 620-10, 620-11, 620-12, 620-13, and 620-14 where two seismic source elements 626-1 and 626-2 are positioned on the outside of the two inner pennants 620-7 and 620-8. In contrast to the example of Figure 3, the transverse line source separation 654 is wider than the transverse line source separation 351 so that the seismic source elements 626-1 and 626-2 are positioned outside the pennants 620-7 and 620-8. The cross-line source separation 654 may be analogous to the cross-line source separation 250 illustrated in FIG. 2. In FIG. 6, the cross-line source separation 654 is based on the cross-line streamer separation 631 (L).

[00054] The transverse line source separation 654 is based on the sum of the integer (k) and the inverse of the quantity of the seismic source elements (1/S) multiplied by the transverse line streamer separation 631 (L) as depicted by the expression (k + 1/S)L. As in the example of Figure 4, the transverse line streamer separation 631 is 100 m and there are two seismic source elements 626. However, in the example of Figure 6, the integer (k) is two. Thus, the 654 transverse line source separation is (2+1/2)*100 m, or 250 m. The seismic source element 626-1 is positioned 75 m to the left of the streamer 6207 and the seismic source element 626-2 is positioned 75 m to the right of the streamer 620-8.

[00055] Although the transverse line source separation 654 is wider than the transverse line source separation 351 of the example of Figure 3 and even wider than the transverse line source separation 450 of the example of Figure 4 , the nominal transverse line subline separation 633 is still one-quarter of the transverse line pennant separation 631 (L/4), or 25 m. The nominal crossline subline separation 633 remains one-quarter of the crossline pennant separation 631 (L/4) without having to increase the number of streamers (N) or decrease the crossline pennant separation (L) 631. By increasing the integer (k) from one as in the example in figure 4 to two, subline coverage 644 is increased from 725 to 775 m. However, the subline cover 644 includes four zero-fold sublines as indicated by the open vertical arrows.

[00056] Figure 7 illustrates a front or back view (yz plane 734) of a configuration of seismic source elements 726-1 and 726-2 and streamers 720-1, 720-2, 720-3, 720-4, 720 -5, 720-6, 720-7, 720-8, 720-9, 720-10, 720-11, 720-12, 720-13, and 720-14 where two seismic source elements 726-1 and 726 -2 are positioned on the exterior of the four inner pennants 720-6, 720-7, 720-8, and 720-9. In contrast to the example of Figure 3, the transverse line source separation 756 is wider than the transverse line source separation 351 so that the seismic source elements 726-1 and 726-2 are positioned outside the pennants 720-7 and 720-8 and outside pennants 720-6 and 720-9. The cross-line source separation 756 may be analogous to a cross-line source separation 250 illustrated in FIG. 2. In FIG. 7, the cross-line source separation 756 is based on a cross-line pennant separation 731 (L ).

[00057] The transverse line source separation 756 is based on the sum of the integer (k) and the inverse of the quantity of the seismic source elements (1/S) multiplied by a transverse line pennant separation 731 (L) as represented by the expression (k + 1/S)L. As in the example of Figure 4, the transverse line streamer separation 731 is 100 m and there are two seismic source elements 726. However, in the example of Figure 7, the integer (k) is three. Thus, the transverse line source separation 756 is (3+1/2)*100 m, or 350 m. The 726-1 seismic source element is positioned 25 m to the left of the 720-6 streamer (125 m to the left of the 720-7 streamer) and the 726-2 seismic source element is positioned 25 m to the right of the 720-9 streamer (125 m to the right of pennant 720-8).

[00058] Although the transverse line source separation 756 is wider than the transverse line source separation 351 of the example of figure 3 and even wider than the transverse line source separation 450 of the example of figure 4 , the nominal transverse line subline separation 733 is still one-quarter of the transverse line pennant separation 731 (L/4), or 25 m. The nominal crossline subline separation remains one-quarter of the 731 crossline pennant separation (L/4) without having to increase the number of streamers (N) or decrease the 731 crossline pennant separation (L). increasing the integer (k) from one as in the example in figure 4 to three increases subline coverage 745 from 725 to 825 m. However, subline coverage 745 includes six zero-fold sublines as indicated by open vertical arrows.

[00059] Figure 8 illustrates a front or back view (yz plane 834) of a configuration of seismic source elements 826-1 and 826-2 and streamers 820-1, 820-2, 820-3, 820-4, 820-5, 820-6, 820-7, 820-8, 820-9, 820-10, 820-11, 820-12, 820-13, and 820-14 where two seismic source elements 826-1 and 826-2 positioned outside the four outer pennants 820-6, 820-7, 820-8, and 820-9. In contrast to the example of Figure 3, the transverse line source separation 858 is wider than the transverse line source separation 351 so that the seismic source elements 826-1 and 826-2 are positioned outside the pennants 820-7 and 820-8 and outside pennants 820-6 and 820-9. The cross-line source separation 858 may be analogous to a cross-line source separation 250 illustrated in FIG. 2. In FIG. 8, the cross-line source separation 858 is based on a cross-line pennant separation 831 (L ).

[00060] The crossline source separation 856 is based on the even integer (ke) multiplied by a crossline streamer separation 831 (L) as represented by the expression keL. As in the example in figure 4, the cross line pennant separation 831 is 100 m. However, in contrast to the example in figure 4, in the example in figure 8 the even integer (ke) is four. Thus, the 856 transverse line source separation is 4*100 m, or 400 m. The 826-1 seismic source element is positioned 50 m to the left of the 820-6 streamer (150 m to the left of the 820-7 streamer) and the 826-2 seismic source element is positioned 50 m to the right of the 820-9 streamer (150 m to the right of pennant 820-8). The nominal 833 transverse line subline separation is half the 831 transverse line pennant separation (L/2), or 50 m. Subline coverage 846 is 850 m, 125 m larger than subline coverage 441 in the example of Figure 4. Subline coverage 846 does not include zero-ply sublines, but does include double-ply sublines as indicated by the thick vertical arrows. Double fold sublines correspond to two coincident or nearly coincident source-receiver midpoints.

[00061] Figure 9 illustrates a front or back view (yz plane 934) of a configuration of seismic source elements 926-1 and 926-2 and streamers 920-1, 920-2, 920-3, 920-4, 920-5, 920-6, 920-7, 920-8, 920-9, 920-10, 920-11, 920-12, 920-13, and 920-14 where two seismic source elements 926-1 and 926-2 positioned outside the four inner pennants 920-6, 920-7, 920-8, and 920-9. In contrast to the example of Figure 3, the transverse line source separation 960 is wider than the transverse line source separation 351 so that seismic source elements 926-1 and 926-2 are positioned outside the pennants 920-7 and 920-8 and outside pennants 920-6 and 920-9. The transverse line source separation 960 may be analogous to a transverse line source separation 250 illustrated in Figure 2.

[00062] In Figure 9, the transverse line source separation 960 is based on a transverse line streamer separation 931 (L). The 960 transverse line source separation is based on the sum of the integer (k) and the inverse of the quantity of seismic source elements (1/S) multiplied by a 931 transverse line pennant separation (L) as represented by the expression (k + 1/S)L. As in the example of Figure 4, the transverse line streamer separation 931 is 100 m and there are two seismic source elements 926. However, in the example of Figure 9, the integer (k) is four. Thus, the 960 transverse line source separation is (4+1/2)*100 m, or 450 m. The 926-1 seismic source element is positioned 75 m to the left of the 920-6 streamer (175 m to the left of the 920-7 streamer) and the 926-2 seismic source element is positioned 75 m to the right of the 920-9 streamer (175 m to the right of pennant 920-8).

[00063] Although the transverse line source separation 956 is wider than the transverse line source separation 351 in the example of Figure 3 and even wider than the transverse line source separation 450 in the example of Figure 4 , the nominal transverse line subline separation 933 is still a quarter of the transverse line pennant separation 931 (L/4), or 25 m, without having to increase the quantity of streamers (N) or decrease the streamer separation of transversal line (L) 931. By increasing the integer (k) from one as in the example in figure 4 to four, the subline coverage 947 increases from 725 to 875 m. However, the subline coverage 947 includes eight zero-fold sublines as indicated by the open vertical arrows. The nominal transverse line subline separation 833 of the example of Figure 8 is L/2. In contrast, the 933 nominal transverse line subline separation is L/4. In Figure 8, there is a full fold subline (indicated by the thin vertical arrows) or a double fold subline (indicated by the thick vertical arrows) every L/2 of the subline cover 846. However, in Figure 9 there is a subline of full fold (indicated by the thin vertical arrows) every L/4 only in the center of the subline cover 947, but at the ends of the subline cover 947 there is a full fold subline every L/2. Full fold sublines correspond to a source-receptor half point.

[00064] Figure 10 illustrates a plan view (yx\ 1032 plane) of marine seismic survey with three seismic source elements 1026-1, 1026-2, and 1026-3. Figure 10 is analogous to Figure 2 except that there are three seismic source elements 1026-1, 1026-2, and 1026-3. The marine seismic survey vessel 1018 may tow one or more seismic source elements, such as seismic source elements 1026-1, 10262, and 1026-3, which may be analogous to the seismic source elements 126 illustrated in Figure 1. The 1026-1, 1026-2, and 1026-3 seismic source elements are collectively referred to as the 1026 seismic source elements.

[00065] Cross line pennant separation 1031 illustrates the spacing of pennant 1020-2 from pennant 1020-3. Although only indicated for streamers 1020-2 and 1020-3, streamer 1020-1 may be spaced apart from streamer 1020-2 by a cross-line streamer separation 1031 and streamer 1020-3 may be spaced apart from streamer 1020-2. streamer 1020-4 by a cross-line pennant separation 1031. The cross-line pennant separation 1031 may be a nominal cross-line pennant separation. The cross-line pennant separation 1031 may be a mid-cross-line pennant separation. When the streamers 1020 are spaced irregularly apart from each other, the transverse line separation 1031 may be the average of the transverse line separation between each of the streamers 1020. For example, the transverse line streamer separation 1031 may be the average of the streamer spacing. pennant 1020-2 from pennant 1020-3, and the spacing of pennant 1020-3 from pennant 1020-4. In at least one embodiment, the streamers 1020 may be towed in a curved path.

[00066] As illustrated in Figure 10, the seismic source element 1026-1 is spaced from the seismic source element 1026-2 by a transverse line source separation 1062 and the seismic source element 1026-2 is spaced apart from the seismic source element 1026-3 by a transverse line source separation 1062. In at least one embodiment, the transverse line source separation 1062 may be directly proportional to a transverse line streamer separation 1031 (L). In at least one embodiment, the transverse line source separation 1062 may be based on an integer (k), an inverse of the quantity of the seismic source elements 1026 (1/S), and the transverse line streamer separation 1031 for private marine research. The transverse line source separation 1062 may be based on a sum of the integer (k) and the inverse of the quantity of the seismic source elements (1/S) multiplied by a transverse line pennant separation (L) as represented by expression (k + 1/S)L. The integer number (k) can be between one and one smaller than the number of pennants (N-1), inclusive. As in the example in figure 10 where there are four streamers 1020, the integer (k) can be 1, 2 or 3.

[00067] In at least one embodiment, the integer (k) can be between one and half the number of pennants (N/2), inclusive. As in the example of Figure 10 where there are four streamers 1020, the integer (k) can be 1 or 2. In at least one embodiment, the integer (k) can be between one and half of a smaller than the number of streamers. streamers ((N-1)/2), inclusive. As in the example in figure 10 where there are four streamers 1020 (N = 4), then the integer range (k) is linked by 1 and 3/2 (1.5). Thus, the integer (k) can be 1.

[00068] Although not illustrated in Figure 10, in at least one embodiment the transverse line source separation 1062 may be the distance between adjacent seismic source subarrays. A first seismic source sub-array, including a plurality of seismic source elements, may be positioned where the seismic source element 1026-1 is positioned in Figure 10. Similarly, a second seismic source sub-array, including a plurality other than seismic source elements, may be positioned where seismic source element 1026-2 is positioned in Figure 10, and a third seismic source subarray, including yet another plurality of different seismic source elements, may be positioned where the 1026-3 seismic source element is positioned in figure 10. If the seismic source elements of a seismic source subarray are actuated together then the location of the seismic source subarray can be grouped together and represented by a point single at the geometric center of the seismic source subarray. The transverse line source separation 1062 may then be the distance between the geometric centers of the first and second seismic source subarrays and the distance between the geometric centers of the second and third seismic source subarrays. In contrast, if the seismic source elements of a seismic source subarray are actuated individually then the transverse line source separation 1062 may be the distance between corresponding seismic source elements of the first and second seismic source subarrays. The first seismic source subarray may include the same or a different amount of seismic source elements as the second or third seismic source subarrays. The second seismic source subarray may include the same amount or a different amount of seismic source elements as the first or third seismic source subarray. The transverse line source separation 1062 may be based on a sum of the integer (k) and the inverse of the quantity of the seismic source subarrays (1/SA) multiplied by a transverse line streamer separation (L) as represented by the expression (k + 1/SA)L.

[00069] As discussed above, a benefit of increasing transverse line source separation may be shorter near-shifts over a large portion of streamers. A wider transverse line source separation may yield shorter near offsets to the outer streamers in a streamer array than for a narrower source separation. For example, in Figure 10 the near offset for the seismic source element 1026-1 and the streamer 1020-1 is the distance from the seismic source element 1026-1 and the receiver 1022-1. The near offset for the seismic source element 1026-1 and the streamer 1020-2 is the distance from the seismic source element 10261 and the receiver 1022-2. 10 illustrates the seismic source elements 1026 being positioned forward of the streamers 1020. However, the seismic source elements 1026 may be positioned above the streamers 1020 such that the seismic source elements 1026 are aft of the front end of the streamer 1020. Therefore, the near deviation of a streamer cannot be the receiver located at the front end of the streamer. The seismic source elements 1026 may be positioned above the streamers 1020 by using longer lines for the seismic source elements 1026 or by having the seismic source elements be towed by another vessel.

[00070] With a wider transverse line source separation, the near offset for streamers near the center of the streamer array, such as streamers 1020-2 and 1020-3, and the near offset for streamers near the edges of the array Streamers such as streamers 1020-1 and 1020-4 can be relatively short (as compared to the near offset distance if the transverse line source separation were smaller). Short near offsets can help in predicting multiples in marine seismic survey data. The predicted multiples can be subtracted from marine seismic survey data. Subtraction of multiples from marine seismic survey data can be performed in any manner known to one of skill in the art.

[00071] Figure 11 illustrates a front or back view (yz plane 1134) of a previous configuration of seismic source elements 1126-1, 1126-2, and 1126-3 and streamers 1120-1, 1120-2, 1120- 3, 1120-4, 1120-5, 1120-6, 1120-7, 1120-8, 1120-9, 1120-10, 1120-11, 1120-12, 1120-13, and 1120-14 where three elements of Seismic sources 1126-1, 1126-2, and 1126-3 are positioned between the two inner streamers 1120-7 and 1120-8. In some prior approaches to marine seismic survey, seismic source elements may be positioned between two internal streamers as illustrated in Figure 11. In Figure 11, the transverse line source separation 1161 between seismic source elements 1126-1 and 1126 -2 and seismic source elements 1126-2 and 1126-3 is a third of the transverse line pennant separation 1131 (L/3). The nominal crossline subline separation 1133 is one-sixth of the crossline pennant separation 1131 (L/6). Subline coverage 1148 shows the length of the subline for this configuration.

[00072] In the example of figure 11, the transverse line streamer separation 1131 is 150 m so that the transverse line source separation 1161 is 50 m. Seismic source element 1126-1 is positioned 25 m to the right of streamer 1120-7, seismic source element 1126-2 is positioned 75 m to the right of seismic source element 1126-1 (midway between streamers 1120 -7 and 1120-8), and the seismic source element 1126-3 is positioned 25 m to the left of the streamer 1120-8. The 1133 nominal transverse line subline separation is 25 m. The coverage of subline 1148 is 1.025 m.

[00073] Figure 12 illustrates a front or back view (yz plane 1234) of a configuration of seismic source elements 12261, 1226-2, and 1226-3 and streamers 1220-1, 1220-2, 1220-3, 1220 -4, 1220-5, 1220-6, 1220-7, 1220-8, 1220-9, 1220-10, 1220-11, 1220-12, 1220-13, and 1220-14 where two of three font elements Seismic beams 1226-1, 1226-2, and 1226-3 are positioned outside the two inner pennants 1220-7 and 1220-8. In contrast to the example of Figure 11, the transverse line source separation 1262 is wider than the transverse line source separation 1161 so that the seismic source elements 1226-1 and 1226-3 are positioned outside the pennants 1220-7 and 1220-8. The transverse line source separation 1262 may be analogous to a transverse line source separation 1062 illustrated in FIG. 10.

[00074] In Figure 12, the transverse line source separation 1262 is based on a transverse line pennant separation 1231 (L). The 1262 transverse line source separation is based on the sum of the integer (k) and the inverse of the quantity of the seismic source elements (1/S) multiplied by a 1231 transverse line pennant separation (L) as represented by the expression (k + 1/S)L. As in the example in figure 11, the cross line pennant separation 1231 is 150 m. In the example of Figure 12, the integer (k) is one and there are three seismic source elements 1226. Thus, the transverse line source separation 1262 is (1+1/3)*150 m, or 200 m. Seismic source element 1226-1 is positioned 25 m to the right of streamer 1220-6, seismic source element 1226-2 is positioned 75 m to the right of streamer 1220-7 (midway between streamers 12207 and 1220- 8) and the seismic source element 1226-3 is positioned 25 m to the left of the pennant 1220-9.

[00075] Although the cross-line source separation 1262 is wider than the cross-line source separation 1161, the nominal cross-line subline separation 1233 is still one-sixth of the cross-line streamer separation 1231 (L /6), or 25 m, as in the example in figure 11 without having to increase the number of pennants (N) or decrease the transverse line pennant separation (L) 1231. The subline coverage 1249 is 1,175 m, 150 m larger than the subline cover 1148 in the example of Figure 11. However, the subline cover 1249 includes six zero-ply sublines as indicated by the open vertical arrows.

[00076] Figure 13A illustrates a front or back view (yz plane 1334) of a configuration of seismic source elements 1326-1 and 1326-2 and streamers 1320-1, 1320-2, 1320-3, 1320-4, 1320-5, 1320-6, 1320-7, 1320-8, 1320-9, 1320-10, 1320-11, 1320-12, 1320-13, and 132014 with two seismic source elements 1326-1 and 1326- 2 positioned on the outside of the four inner streamers 1320-6, 1320-7, 1320-8, and 13209. Figure 13A is the same as Figure 7 and illustrates the same configuration of the fourteen streamers 1320-1 to 1320-14 and two seismic source elements 1326-1 and 1326-2. As in the example in Figure 7, the transverse line streamer separation 1331 is 100 m, there are two seismic source elements 1326, and the integer (k) is three. Thus, the transverse line source separation 1356 is (3+1/2)*100 m, or 350 m. The nominal 1333 transverse line subline separation is one-quarter of a 1331 transverse line pennant separation, or 25 m. The coverage of subline 1345 is 825 m; however, subline coverage 1345 includes six zero-fold sublines as indicated by open vertical arrows.

[00077] Figure 13B illustrates a plan view (yx plane 1332) of sublines for consecutive actuations of seismic source elements 1326-1 and 1326-2 associated with the configuration of an arrangement of seismic source elements 1326-1 and 1326- 2 and pennants 1320 for a navigation line. In Figure 13B, the zero bend sublines 1370 are dashed and correspond to the vertical arrows illustrated in Figure 13A. Full fold sublines, such as full fold subline 1372, are solid and correspond to nominally recorded data corresponding to source-receiver midpoints illustrated in Figure 13A. As used herein, "nominally recorded data" refers to situations where the recorded data corresponds to points other than the source-receiver midpoints.

[00078] Figure 13B illustrates the gaps in the subline coverage 1345, represented by the zero-fold sublines 1370, and indicated by the vertical arrows in Figure 13A. A zero fold does not necessarily imply a complete lack of marine seismic survey data corresponding to the 1370 zero fold sublines. The zero fold sublines can perfectly assume uniform source and receiver geometry with parallel streamers. However, in practice, seismic source elements, receivers, and streamers move around so that there may be some recorded data that correspond to the zero-fold sublines. Zero or very low bend sublines can affect the transverse line resolution of marine seismic survey data because zero or very low bend sublines can become negligible or no contribution to a total seismic image at locations corresponding to zero or very low bend sublines. lows. As a result, a marine seismic image generated from marine seismic survey data may have a lower resolution at the edges of a sail than the transverse line resolution at the center of the navigation line as illustrated in Figure 13B.

[00079] Figure 14 illustrates a plan view or yx plane 1432 of a cross-line navigation line separation 1480 between two adjacent navigation lines 1482-1 and 1482-2 so that there is no overlap of the sublines. As used herein, "separation of navigation line from transverse line" refers to the distance in the transverse direction between two adjacent navigation lines. As used herein, "nominal crossline navigation line separation" refers to a crossline navigation line separation such that there is no overlap of the sublines corresponding to adjacent navigation lines. The sublines illustrated in Figure 14 correspond to the configuration of the streamers and seismic source elements illustrated in Figures 7 and 13A and two sets of the sublines illustrated in Figure 13B placed side by side. However, Figure 14 shows sublines corresponding to the configuration of the streamers and seismic source elements illustrated in Figures 7 and 13A along two adjacent navigation lines 1482-1 and 1482-2. Arrows on navigation lines 1482-1 and 14822 do not limit the direction of navigation. Navigation lines 1482-1 and 1482-2 can be oriented in opposite directions. Sublines corresponding to navigation line 1482-1 are identified by square bracket 1484-1 and sublines corresponding to navigation line 1482-2 are identified by square bracket 1484-2. Vertical dashed line 1477 represents a midline midway between navigation line separation and transverse line 1480. In Figure 14, zero bend sublines 1470-1 and 1470-2 are dashed while full bend sublines, such as the complete fold sublines 1472-1 and 1472-2 are solid. Zero-fold sublines 1470-1 and full fold 1472-1 correspond to navigation line 1482-1 while zero-fold sublines 1470-2 and full fold 1472-2 correspond to navigation line 1482-2.

[00080] As illustrated in Figure 14, performing a marine seismic survey may include cross-line navigation line separation 1480 being a nominal cross-line navigation line separation. The rightmost subline corresponding to navigation line 1482-1 is adjacent to the leftmost subline corresponding to navigation line 1482-2. The rightmost subline corresponding to navigation line 1482-1 may be spaced apart from the leftmost subline corresponding to navigation line 1482-2 by nominal transverse line subline separation 1433. Separation of navigation line from transverse line nominal can be the number of sublines multiplied by a transverse line subline separation for a navigation line. Based on the configuration of the arrangement of the streamers and seismic source elements illustrated in Figures 7 and 13A, in the example of Figure 15 there are thirty-four fold sublines and the transverse line subline separation is 25 m so that the bend line separation transverse line navigation 1480 is 850 m.

[00081] Although a zero bend does not necessarily imply a complete lack of marine seismic survey data corresponding to zero bend sublines 1470-1 and 1470-2 as discussed above, zero or very low bend sublines may affect line resolution cross-sectional view of marine seismic survey data because zero or very low fold sublines may become insignificant and make no contribution to a total seismic image at locations corresponding to zero or very low fold sublines. As a result, a marine seismic image generated from marine seismic survey data from two adjacent shipping lines, such as shipping lines 1482-1 and 1482-2, may have a lower resolution at the edges of a combined surveyed area. additional navigation lines (not illustrated in figure 14) can cause an alternate pattern in the higher resolution and lower resolution marine seismic survey image as well as alternate image quality in the direction of the transverse line.

[00082] Figure 15A illustrates a plan view (yz plane 1532) of sublines for two adjacent navigation lines 1582-1 and 1582-2 where a navigation line separation from transverse line 1581 is such that there is an overlap of the sublines . If nominal transverse line navigation line separation is used such that sublines corresponding to one navigation line do not overlap sublines corresponding to an adjacent navigation line as illustrated in FIG. 14. At least one embodiment may include separation Due to the cross-line navigation line separation 1581 which is less than the nominal cross-line navigation line separation 1480 as illustrated in Figure 14. Due to the cross-line navigation line separation 1581 which is less than the line separation nominal transverse line navigation, some of the sublines corresponding to navigation line 1582-1 (identified by bracket 1584-1) overlap with some of the sublines corresponding to navigation line 1582-2 (identified by bracket 1584-2). Zero warp sublines corresponding to navigation line 1582-1 are spatially coincident with full warp sublines corresponding to navigation line 1582-2 and vice versa.

[00083] Figure 15A shows the corresponding sublines along two adjacent navigation lines 1582-1 and 1582-2 for the configuration of the streamer array and seismic source elements illustrated in Figures 7 and 13A. The arrows on navigation lines 1582-1 and 1582-2 do not limit the navigation direction. Navigation lines 1582-1 and 1582-2 can be oriented in opposite directions. Vertical dashed line 1577 represents a halfway line between navigation line separation and transverse line 1581. In Figure 15A, zero fold sublines 1570 are dashed while full fold sublines, such as fold sublines complete 1572, are solid. No zero-fold sublines, such as the zero-fold sublines 1470-1 and 1470-2 illustrated in Figure 14, are evident in the overlap zone between adjacent navigation lines 1582-1 and 1582-2.

[00084] Cross-line navigation line separation 1581 may be based on the configuration of streamers and seismic source elements. A particular configuration of streamers and seismic source elements, such as those illustrated in Figures 7 and 13A, may cause a particular pattern of full bend sublines and zero bend sublines in the outer areas of each navigation line. Thus, the separation of navigation line from transverse line 1581 may be such that some of the full fold sublines of one navigation line complement some of the zero fold sublines of an adjacent navigation line, and vice versa.

[00085] As illustrated by the example of Figure 15A, the full fold sublines corresponding to navigation line 1582-1 complement, or "fill in", the zero fold sublines corresponding to navigation line 1582-2. Similarly, the full fold sublines corresponding to the navigation line of navigation line 1581-2 complement or "fill in" the zero fold sublines corresponding to navigation line 1582-1. Thus, transverse line resolution and seismic image quality can be maintained across the overlap zone between adjacent navigation lines 1582-1 and 1582-2. However, the leftmost zero-fold sublines corresponding to navigation line 1582-1 and the rightmost zero-fold sublines corresponding to navigation line 1582-2 may be complemented, or "filled in," by the leftmost zero-fold sublines corresponding to navigation line 1582-1. complete corresponding to additional adjacent navigation lines (not illustrated in Figure 15A).

[00086] To have the full fold sublines corresponding to the navigation line, the navigation line 1581-2 complements or "fills in" the zero fold sublines corresponding to the navigation line 1581-1 and vice versa, the line separation crossline navigation 1581 may be the number of complete fold sublines between adjacent navigation lines 1582-1 and 1582-2 multiplied by a crossline subline separation. In the example of Figure 15, there are twenty-eight full warp sublines between adjacent navigation lines 1582-1 and 1582-2 and the transverse subline separation is 25 m so that a transverse navigation line separation 1581 is 700 m. The cross-line navigation line separation 1581 may be the same as the nominal cross-line navigation line separation for the configuration of streamers and seismic source elements as in the example of Figure 3 along adjacent navigation lines as in example in figure 14.

[00087] Figure 15B illustrates a plan view (yx plane 1532) of sublines for two adjacent navigation lines 1582-1 and 1582-2 where the separation of navigation line from transverse line 1581 is such that there is an overlap of the sublines . Figure 15B shows the same navigation line separation 1581 as Figure 15A, but the sublines corresponding to the navigation line 1582-1 (identified by the bracket 1584-1) are illustrated above the sublines corresponding to the navigation line 1582-2 ( identified by bracket 1584-2). Zero-fold sublines 1570-1 and full-fold sublines 1572-1 correspond to navigation line 1582-1 while zero-fold sublines 1570-2 and full-fold sublines 1572-2 correspond to navigation line 1582- two. 15B illustrates that the full fold sublines 1572-1 complement or "fill in" the zero fold sublines 1570-2 and the full fold sublines 1572-2 complement or "fill in" the zero fold sublines 1570-1.

[00088] At least one embodiment may include inducing a streamer diffusion angle that is greater than zero degrees to move the streamers. Moving the streamers can ensure that receivers located at the rear ends of the streamers contribute to all sublines corresponding to a particular navigation line regardless of any prevailing conditions. When a streamer diffusion angle is induced, the cross-line source separation can be based on the nominal cross-line streamer separation.

[00089] Figure 16 illustrates a method for a marine seismic survey. The method may comprise, in block 1690, towing streamers that are spaced in one direction from the transverse line by a streamer separation (L). In block 1692, the method may include towing seismic source elements that are spaced apart in the direction of the transverse line by a source separation based on an integer (k), an inverse of a quantity of the seismic source elements (1/S). , and the streamer separation as represented by (k + 1/S)L.

[00090] Although not illustrated in Figure 16, the method may include determining a value of the integer (k) based on a quantity of streamers (N). The method may include determining a value of the integer (k) between one and one less than a quantity of the plurality of streamers (N-1), inclusive, between one and one-half of the quantity of the plurality of streamers (N/2), inclusive, or between one and half of one less than the quantity of the plurality of pennants ((N-1)/2), inclusive.

[00091] Although not illustrated in Figure 16, the streamers and seismic source elements can be towed by a marine research vessel. The streamers can be towed by a first marine research vessel and the seismic source elements can be towed by a second marine research vessel. The streamers may be towed by a first marine research vessel, a first of the seismic source elements may be towed by a second marine research vessel, and a second of the seismic source elements may be towed by a third marine research vessel.

[00092] In block 1694, the method may include actuating the seismic source elements. In block 1696, the method may include detecting seismic signals at each of a plurality of receivers on the streamers.

[00093] Figure 17 illustrates a method for a marine seismic survey. The method may include, in block 1791, determining a number of streamers of an array. In block 1793, the method may include determining a number of seismic source elements of the array. In block 1795, the method may include performing a marine seismic survey with a plurality of seismic source elements and a plurality of streamers, wherein a transverse line source separation between each of the seismic source elements is directly proportional to a cross line pennant separation (L) between each of the pennants. The cross-line source separation may be directly proportional to a cross-line streamer separation (L) by a sum of an integer (k) less than or equal to a quantity (N) of the plurality of streamers and an inverse of a quantity of seismic source elements (1/S).

[00094] Although not illustrated in Figure 17, the method may include determining an integer value (k) for a particular subline coverage. The value of the integer (k) can be increased to increase subline coverage. The method may include maintaining a marine seismic survey resolution while increasing transverse line source separation, without increasing the quantity (N) of the plurality of streamers.

[00095] Although not illustrated in figure 17, marine seismic survey can be carried out together with two or more adjacent navigation lines. A cross-line navigation line separation between the two adjacent navigation lines may be such that a subline of one of the two adjacent navigation lines complements a subline of another of the two adjacent navigation lines. The cross-line navigation line separation between the two adjacent navigation lines may be such that a full warp subline of one of the two adjacent navigation lines complements a zero-fold subline of the other of the two adjacent navigation lines. A transverse line subline separation between the complement sublines of one of the two adjacent navigation lines and the complement sublines of the other of the two adjacent navigation lines may be maintained. The method may include subtracting a predicted multiple from the marine seismic survey data.

[00096] According to a number of embodiments of the present disclosure, a geophysical data product can be produced. Geophysical data can be obtained and stored in a tangible, non-transitory, computer-readable medium. The processed data can be recorded on a non-transitory machine-readable medium, thereby creating the geophysical data product. The geophysical data product may include, for example, field data recorded during a survey using the techniques described above. In some cases, geophysical analysis may be performed on the marine geophysical data product in accordance with techniques described herein or known in the art, and stored on a computer-readable medium to produce an improved geophysical data product.

[00097] Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the present disclosure, even where only a single embodiment is described with respect to a particular resource. The examples of features provided in the disclosure are intended to be illustrative rather than restrictive unless otherwise described. The above description is intended to cover such alternatives, modifications and equivalents as may be apparent to one skilled in the art having the benefit of this disclosure.

[00098] The scope of the present disclosure includes any feature or combination of features disclosed herein (whether explicitly or implicitly), or any generalization thereof, whether or not it alleviates any or all of the problems addressed herein. Various advantages of the present disclosure have been described herein, but embodiments may provide some, all, or none of such advantages, or may provide other advantages.

[00099] In the Detailed Description above, some resources are grouped together in a single modality for the purpose of optimizing dissemination. This method of disclosure should not be construed as reflecting an intention that the disclosed embodiments of the present disclosure have to use more features than are expressly described in each claim. Preferably, as the following claims reflect, the subject matter of the invention lies in less than all of the features of a single disclosed embodiment of a disclosed embodiment. Accordingly, the following claims are incorporated herein in the Detailed Description, with each claim standing by itself as a separate embodiment.

Claims (23)

1. Method for a marine seismic survey, comprising: towing streamers (1690) that are spaced apart in a transverse line direction by a streamer separation (L); tow seismic source elements (1692) that are spaced apart in the transverse line direction by a source separation, characterized in that the source separation is based on an integer (k), an inverse of a quantity of the source elements seismic (1/S), and the separation of streamers as represented by (k+1/S)L; actuate seismic source elements (1694); and detecting seismic signals (1696) at each of a plurality of receivers on the streamers. 2. Method, according to claim 1, characterized by the fact that it further comprises determining a value of the integer (k) based on a quantity of streamers (N). 3. Method, according to claim 1, characterized by the fact that it further comprises determining a value of the integer (k) between one and one less than a quantity of the plurality of streamers (N-1), inclusive. 4. Method, according to claim 1, characterized by the fact that it further comprises determining a value of the integer (k) between one and half of the quantity of the plurality of streamers (N/2), inclusive. 5. Method according to claim 1, characterized by the fact that it further comprises determining a value of the integer (k) between one and half of one less than the quantity of the plurality of streamers (N-1)/2) , including. 6. The method of claim 1, wherein towing the streamers and towing the seismic source elements includes towing the streamers and the seismic source elements by a marine research vessel. 7. The method of claim 1, wherein towing the streamers includes towing the streamers by a first marine seismic survey vessel, and towing the seismic source elements includes towing the seismic source elements by a second marine research vessel. 8. The method of claim 1, wherein towing the streamers includes towing the streamers by a first marine seismic survey vessel, and towing the seismic source elements includes: towing a first of the seismic source elements by a second marine research vessel; and towing a second of the seismic source elements by a third marine research vessel. 9. Method according to claim 1, characterized by the fact that the integer (k) is less than or equal to the quantity (N) of the plurality of streamers. 10. The method of claim 9, further comprising determining an integer value (k) for a particular subline coverage. 11. Method, according to claim 9, characterized by the fact that it further comprises increasing a subline coverage by increasing an integer value (k). 12. The method of claim 9, further comprising maintaining a marine seismic survey resolution while increasing transverse line source separation; without increasing the quantity (N) of the plurality of streamers. 13. The method of claim 9, further comprising performing the marine seismic survey together with two adjacent navigation lines using a cross-line navigation line separation between the two adjacent navigation lines so that a subline of one of the two adjacent navigation lines complements a subline of another of the two adjacent navigation lines. 14. The method of claim 9, further comprising performing the marine seismic survey together with two adjacent navigation lines using a cross-line navigation line separation between the two adjacent navigation lines so that a full warp subline of one of the two adjacent navigation lines complements a zero warp subline of another of the two adjacent navigation lines. 15. The method of claim 14, further comprising maintaining a crossline subline separation between the complement sublines of one of the two adjacent navigation lines and the complement sublines of the other of the two navigation lines. adjacent navigation. 16. Method according to claim 9, characterized by the fact that it further comprises subtracting a predicted multiple from marine seismic survey data. 17. Method according to claim 1, characterized by the fact that the method further comprises: recording the detected seismic signals on a non-transitory machine-readable medium, thereby completing the manufacture of a geophysical data product. 18. Method, according to claim 17, characterized by the fact that it further comprises processing the seismic signals detected offshore before the recording step. 19. Arrangement comprises: a plurality of seismic source elements configured to be towed by a marine research vessel, characterized by the fact that a transverse line source separation between adjacent seismic source elements (1795) is at least based on: an integer (k); a separation of transverse line streamers (L) between each of a plurality of streamers to be towed by the marine survey vessel for a particular marine seismic survey; and an inverse of a quantity of the plurality of seismic source elements (1/S). 20. Arrangement according to claim 19, characterized by the fact that the transverse line source separation is a sum of the integer (k) and the inverse of the quantity of the plurality of seismic source elements (1/S) that are adjacent in a crossline direction multiplied by the crossline streamer separation (L). 21. Arrangement according to claim 19, characterized by the fact that the transverse line pennant separation (L) is a mid-transverse line pennant separation. 22. The arrangement of claim 19, wherein the plurality of seismic source elements comprises a first seismic source sub-array, wherein the arrangement further comprises a second seismic source sub-array comprising a plurality other than seismic source elements, wherein the first seismic source subarray is adjacent to the second seismic source subarray, and wherein the transverse line source separation is a distance between the first seismic source subarray and the second seismic source sub-array and is based on: the integer (k); in the separation of the transverse line pennant (L); and in an inverse of a number of seismic source subarrays (1/SA). 23. Arrangement according to claim 19, characterized by the fact that the transverse line source separation is greater than the transverse line streamer separation (L).