Modular foil system for towed marine array

A marine array having various embodiments of a modular foil system is disclosed. The modular foil system may be configured to generate lift when towed in a marine environment, and thus used to move, position, and/or depress instrument of the array. The modular foil system may include multiple groups of foil sections, each having an angle of attack that is adjustable relative to other groups of foil sections. For example, each group may be supported by a pair of through cables, and an actuator may adjust a tension in one or both of through cables, thereby alerting the angle of attack. The pair of through cables may converge toward one another at connection points adjacent opposing ends of a given group of foil sections of the modular system. The connection points thus establishing a modular framework to couple the given group to other groups of foils of the system.

FIELD

The described embodiments relate generally to towed marine arrays. More particularly, the present embodiments relate to system and techniques for controlling hydrodynamic foil orientation in the marine array.

BACKGROUND

In towed marine seismic exploration, a hydrophone array is typically towed behind a marine vessel near the sea surface. The hydrophones are mounted to multiple sensor cables, commonly referred to as streamers. The streamers serve as platforms or carriers for the hydrophones, which are distributed along the length of each streamer in the array.

A set of seismic sources, also towed near the sea surface, are operated to periodically emit acoustic energy. The acoustic energy of interest propagates downward through the seawater (or other water column), penetrates the ocean floor, reflects from the subsea strata and other underlying structures, and returns upward through the water column to the hydrophone array.

The reflected seismic energy (or acoustic wave energy) arrives at receiver points in the towed hydrophone array. The array includes many such receiver points, distributed along each of the streamer cables, with sensors configured to generate data records characterizing the upward-traveling acoustic wavelets (or seismic waves) received from the subsurface structures beneath the seabed, at each of the receiver points. The hydrophone data recordings are later processed to generate seismic images of the underlying structure.

In the field of subsea seismic exploration, there has recently been a demand for seismic equipment operators to conduct their surveys with the seismic equipment submerged below the depths at which most seismic surveys have been conducted in the past. These new, deeper operating targets can now lie well below the depth of the surface-referenced equipment (i.e., the vessel and the paravanes) that is used to tow and laterally spread the seismic sensors.

Typical marine depressors for maintaining equipment at a substantially constant submerged depth tend to be fairly small with very poor aspect ratios, thus resulting in low lift. Aspect ratio is defined as the span of the depressor divided by its chord line length. Wings with high aspect ratios generate high downward lift forces for minimal drag (such that lift-to-drag ratios as high as 10:1 or more are possible), whereas wings with aspect ratios as low as 1 or 2 (i.e., where span and chord are roughly the same scale) will typically have lift-to-drag ratios as low as 2:1, or even lower. Conventional depressors can often also provide payload bays which can be used to hold additional ballast to supplement the downforce generated by the depressor.

The problem with using deadweight to generate downforce is that it does not scale with tow speed—it provides a constant downforce regardless of how fast the depressor is moving through the water. This is often disadvantageous for those applications where a range of operational speeds is expected, with the requirement that the towed equipment maintain a stable depth over that speed range. Consequently, there is no easy, economical, or ideal way to submerge and operate seismic equipment, such as towed streamer cables, at the desired lower depths.

SUMMARY

Embodiments described in the present disclosure are directed to controlling an angle of attack for submerged foils of a marine array. Foil sections may be coupled to one another by a pair of cables that converge toward one another at connection points adjacent to opposing ends of the foils. An actuator may be coupled to the cables and configured to adjust tension in the cables, thereby altering an angle of attack of the foils.

In an embodiment, a marine array is disclosed. The marine array includes a cable configured to be towed by a vessel and carry a payload through a marine environment. The marine array further includes a modular foil system coupled with the cable and configured to bias the payload toward a target position. The modular foil system includes a group of foil sections collectively defining an angle of attack. The modular foil system further includes a pair of through cables supporting the group of foil sections within the modular foil system and converging toward a connection point.

In another embodiment, the marine array may further include an actuator configured to alter a tension in one or both of the pair of through cables, thereby altering the angle of attack. In some cases, the group of foil sections is a first group of foil sections defining a first angle of attack. The pair of through cables is a first pair of through cables. In this regard, the modular foil system may further include a second group of foil sections collectively defining a second angle of attack. The modular foil system may further include a second pair of through cables supporting the second group of foil sections within the modular foil system and converging toward the connection point.

In another embodiment, the second angle of attack is distinct from the first angle of attack. The marine array may further include an actuator configured to alter a tension in one or both of the first pair of through cables, thereby altering the first angle of attack relative to the second angle of attack.

In another embodiment, the payload is an instrument configured to at least one of either collect data or transmit data. The target position may include at least one of a lateral position or a depth position.

In another embodiment, the cable may be a first cable towed by the vessel. The marine array may further include a second cable towed by the vessel. The modular foil system may be arranged substantially between submerged portions of the first cable and the second cable.

In another embodiment, the cable is a cross-cable. The marine array may further include streamer cables configured to be towed behind the cross-cables. The payload may include seismic receivers carried by the streamer cables. The angle of attack may be configured to maintain the seismic receivers at a desired depth.

In another embodiment, the cable is a lateral cable of the marine array under tension. The lateral cable includes an end portion positioned along an edge of the marine array. As such, the modular foil system may be coupled with the lateral cable adjacent the end portion.

In another embodiment, the marine array may further include a spur line connected to the end portion of the lateral cable. The modular foil system may be connected to the spur line opposite the lateral cable.

In another embodiment, the cable is an upper cable. The marine array may further include a lower cable. In some cases, the upper cable and the lower cable cooperate to form a mouth of a fishing trawl. The modular foil system may be configured to increase a separation between the upper cable and the lower cable at the mouth of the fishing trawl. Additionally or alternatively, the modular foil system may be configured to laterally spread the upper cable and the lower cable.

In another embodiment, a modular foil system for biasing a cable of a marine array is disclosed. The modular foil system includes a group of foil sections defining a foil shape having a leading edge and a trailing edge. The modular foil system further includes a first through cable extending through the group of foil sections along the leading edge. The modular foil system further includes a second through cable extending through the group of foil sections along the trailing edge. The modular foil system further includes an actuator configured to adjust a tension in one or both of the first through cable or the second through cable. The first through cable and the second through cable converge at connection points adjacent opposing ends of the group of foil sections.

In another embodiment, the actuator may be a dynamic actuator configured to alter the tension in one or both of the first pair of through cables while submerged in a marine environment. Each of the connection points may be configured to couple a pair of through cables from another modular foil system of the marine array to the first through cable and the second through cable. In some cases, at least one of the connection points is defined by a ring and at least one of the pair of through cables extends through the ring.

In another embodiment, the group of foil sections defines a first duct along the leading edge of the foil shape and a second duct along the trailing edge of the foil shape. The first through cable extends through the first duct. The second through cable extends through the second duct. The group of foil sections may be configured to move within the foil system along the first through cable and the second through cable.

In another embodiment, the actuator is coupled to the first through cable. The actuator is a first actuator. The foil system further comprises a second actuator coupled to the second through cable. The first through cable and the second through cable are integral portions of a continuous cable.

In another embodiment, a method of positioning a modular foil system in a marine array is disclosed. The method includes launching an array into a marine environment, the array comprising a cable configured to carry a payload and a modular foil system coupled to the cable. The method includes acquiring submerged positional data associated with the modular foil system. The method includes determining an adjustment parameter for the modular foil system by comparing the submerged positional data with an operational target. The method includes adjusting an angle of attack of a first group of foil sections of the modular foil system using the adjustment parameter.

In another embodiment, the group of foil sections is supported within the modular foil system by a pair of through cables that converge toward a connection point. The method may further include controlling a tension in one or both of the first pair of through cables using a dynamic actuator. The dynamic actuator may be responsive to the adjustment parameter.

In another embodiment, a marine array is disclosed. The marine array includes a cable configured to be towed by a vessel and a submerged payload through a marine environment. The marine array includes a modular foil system coupled with the cable and configured to bias the submerged payload toward a target position. The modular foil system includes a first group of foil sections having a first angle of attack. The modular foil system further includes a second group of foil sections having a second angle of attack. The first angle of attack is adjustable relative to the second angle of attack.

In another embodiment, the modular foil system further comprises a first pair of through cables. The first group of foil sections is supported in the modular foil system by the first pair of through cables. The first pair of through cables converge toward a connection point, and the connection point couples the first group of foil sections to a discrete assembly of the marine array.

In another embodiment, the marine array includes an actuator configured to alter a tension in one or both of the first pair of through cables, thereby altering the first angle of attack. The actuator may be a dynamic actuator configured to alter the tension in one or both of the first pair of through cables while submerged in the marine environment. In some cases, the actuator is a turnbuckle coupled to one of the first pair of through cables.

In another embodiment, the modular foil system further comprises a second pair of through cables. The second group of foil sections is supported in the modular foil system by the second pair of through cables. The second pair of through cables converge toward the connection point. The second group of foil sections is the discrete assembly coupled to the first group of foil sections at the connection point.

In another embodiment, the cable is a cross-cable. The marine seismic array further includes streamer cables configured to be towed behind the cross-cables. The payload includes seismic instruments carried by the streamer cables. Both of the first angle of attack and the second angle of attack are configured to maintain the seismic receivers at a desired depth.

In another embodiment, the marine array includes a pair of diverters positioned at opposing ends of the cross-cable and configured to laterally spread the cross-cable when towed in the marine environment. The pair of diverters may be configured to provide a positive lift to the cross-cables along a substantially vertical direction. The modular foil system may be configured to provide a negative lift to the cross-cable along the substantially vertical direction, the negative lift operating to counteract the positive lift provided by the pair of diverters.

DETAILED DESCRIPTION

The description that follows includes sample systems, methods, and apparatuses that embody various elements of the present disclosure. However, it should be understood that the described disclosure may be practiced in a variety of forms in addition to those described herein.

The following disclosure describes systems, devices, and techniques related to controlling an orientation of foil systems of a marine array. The foil systems may be used to control movements and/or maintain a position of various instruments, devices, assemblies and so forth of the marine array. For example, a foil system may include a group of foil sections that cooperate to define a foil shape having a leading edge and a trailing edge. The group of foil sections may be coupled to instruments of the array. When towed, the group of foil sections may generate lift (e.g., including a lateral lift, a perpendicular lift and so on), due in part to an orientation or “angle of attack” of the foil shape. In turn, this lift may be used to correspondingly move instruments coupled to the foil system. The foil sections defining the foil shape may be coupled together by a through cable and/or other mechanism allowing the foil sections to move relative to one another in a dynamic marine environment. However, such movement may limit the orientation of the foil shape and/or other otherwise distort the shape due to hydrodynamic forces.

The foil system of the present disclosure may mitigate such hindrances, thereby allowing the group of foil sections to be arranged at a variety of orientations (e.g., a variety of attack angles). The foil system may be configured to generate different lifts for each orientation or angle of attack. For example, at a first angle of attack the foil system may generate a first lift, whereas at a second angle of attack the foil system may generate a second lift, distinct from the first lift. The foil system may be coupled with instruments of the marine array, as described herein, and thus each of the first lift, the second lift, or other lift may cause the coupled instruments to be steered or positioned in a desired manner. The orientation or angle of attack may be adjusted while the foil system is towed. Accordingly, the foil system may be adaptable to dynamic conditions of a marine environment and/or to particular instruments and requirements of the marine array.

To facilitate the foregoing, the foil system of the present disclosure may be configured to adjust a tension in one or more cables that support the foil sections within the marine array. For the sake of non-limiting illustration, the foil system may include a group of foil sections that are arranged adjacent one another to define the foil shape. A pair of through cables may extend through one or more of, or each of, the group of foil sections, thereby coupling the foil sections to one another and allowing for relative movement between adjacent foil sections.

When deployed, the pair of through cables may have a tension that generally allows the foil sections to orientate at an equilibrium position. The tension in one or both of the through cables may be adjusted in order to modify the orientation or angle of attack, and therefore modify a lift generated by the foil system. For example, one or more actuators may be coupled with the pair of through cables. The actuator may be configured to increase a tension in one or both of the pair of through cables. As the tension is increased, movement of foil sections relative to one another may be diminished, and the group of adjacent foil sections may collectively orientate toward, for example, an enhanced attack. The enhanced angle of attack may generate greater lift, and thus the foil system may exert a greater force on coupled instruments of the array, which may help steer or depress the instruments toward a desired position.

In turn, the foil system may also operate to diminish the angle of attack by reducing tension in the pair of through cables. For example, the actuator may operate to reduce the tension in one or both of the pair of through cables. The reduced tension may allow the foil sections to return toward the equilibrium position, thereby resulting in a diminished angle of attack. The diminished angle of attack may generate less lift, and thus the foil system, may exert a lesser force on the coupled instruments of the array. This may help steer or depress the instruments toward a desired position.

The actuator, as described herein, may be substantially any appropriate component that is used to adjust a tension in a cable. In one embodiment, the actuator may be a mechanical component, such as a turnbuckle. The turnbuckle may be manually adjusted, for example, prior to deployment of array, in order to set a desired angle of attack of the foils. Additionally or alternatively, the foil system may include various dynamic actuator, such as a pneumatic, hydraulic, or electromechanical controller that is used to modify a tension in the pair of through cables. It will be appreciated, however, that other actuators are possible and contemplated with the scope of the present disclosure.

In some cases, the actuator may be configured to adjust a tension of the cable while the array is deployed in a marine environment. For example, the actuator may be configured to receive a signal from another source, such as a vessel towing the array, or another remote source. The actuator may use the signal to adjust a tension in the cable. For example, in a first configuration, the signal may be indicative of a first desired orientation and the actuator may adjust a tension in the through cable in order for the foil section to match the first desired orientation. Likewise, in another configuration, the signal may be indicative of a second desired orientation and the actuator may adjust a tension in the through cable in order for the foil section to match the second desired orientation.

The actuator may therefore be used for dynamic or real-time, “on-the-fly” positioning of instrument of the marine array. Continuing the non-limiting illustration, the first desired orientation of the group of foil sections may correspond to a target lift generated by the foil section in order to position instruments of the array in a desired location (or submerged depth). Conditions may change in the marine environment, for example, due to unpredictable hydrodynamic forces, marine debris or obstacles, and so forth, including changes in course for the vessel itself. It may thus be desirable to reposition instruments of the array. Stated differently, it may be desirable to exert different forces on the instrument in order to account for the changing conditions.

The second desired orientation of the above illustration may correspond to such different force, and thus the actuator may help account for the changing condition. In some cases, the array may employ various sensors to detect the changing conditions. The actuator may be coupled with these sensors, and thus automatically compensate for the changing condition by altering the tension in the coupled through cables.

The foil systems of the present disclosure may serve a variety of functions in a marine array, as describe herein. For example, in one configuration, the foil sections may define a foil shape that extends substantially laterally through a marine environment. When orientated at a negative angle of attack, the foil sections may generate negative lift that biases the foil sections deeper into a marine environment. The foil section in such configuration may therefore function as a depressor that operates to maintain coupled instruments at a desired depth. As another example, in a second configuration, the foil sections may define a foil shape that extends substantially perpendicularly through the marine environment. When orientated at an angle of attack, the foil section may generate a lift that biases the foil sections laterally in the marine environment. The foil section in such configuration may therefore function as a steering or positioning device that operates to cause coupled instruments to move toward a desired position. In other configurations, other lifts may be possible, including a configurations in which the foil sections generate combination of perpendicular and lateral lifts.

In order to facilitate coupling of the foil systems described herein to various instruments of that array, the through cables may converge toward a connection point. For example, the group of foil sections may be arranged adjacent to one another to define a foil shape having a first end (e.g., a first longitudinal end) and a second end (e.g., a second longitudinal end). The through cables may extend through ducts defined in one or more of, or each of, the foil sections and converge toward one another at each of the first end and the second end. In particular, the pair of through cables may convergence toward one another at a first connection adjacent the first end of the foil shape. Likewise, the pair of through cables may converge toward one another at second connection adjacent the second end of the foil shape. The convergence of the cables may help regulate tension in the through cables, and therefore allow for more accurate or precise control of foil shape angle of attack.

The pair of through cables may converge toward a connection point adjacent an end of a foil section groups, and as such, define a triangular shape with an endmost one of the foil sections. As described herein, the triangular shape may change according to a magnitude of the tension in one or both of the through cables of the foil system. For example, the actuator may be associated with a through cable adjacent a leading edge of the foil sections, and when in a neutral or unactuated state, the through cables may form a triangle shape with the endmost foil section that substantially resembles a right triangle (e.g., with a substantially ninety degree angle formed between the leading edge through cable and the endmost foil section). As the actuator operates to decrease the tension in the leading edge cable, thereby increasing tension in the trailing edge cable (e.g., to adjust the angle of attack), the triangular shape will change, such as changing into a shape substantially resembling an isosceles triangle. Yet further, the actuator may operate to increase or decrease the tension, and further manipulate the angle defined by the leading edge through cable and the endmost foil section. This dynamic triangular shape may help facilitate fine control of the angle of attack, while also allowing the foil section angle of attack to be modified relative to other modules of a modular foil array.

For example, the convergence of the through cable may allow the foil system to be an assembly of a modular foil system. For example, as described herein, a first group of foil sections may define a first foil shape and a second, distinct group of foil sections may define a second foil shape. The first group of foil sections may be coupled to the second group of foil sections by one or more pairs of through cables that converge at a connection point positioned substantially between the distinct groups of foils. In this manner, distinct groups of foil sections may be “daisy-chained” to one another across a span of the marine array. This may also allow for more accurate or precise control of a tension in the through cables as the tension may be adjusted in each individual “module” (e.g., adjacent each distinct group of foil sections).

Adjusting the tension in through cables adjacent individual groups of foil sections may allow for distinct angles of attack of foil sections along the modular system. For example, a first group of foil sections may have a first angle of attack based on a first tension in the through cable supporting the first foil sections in the array. Further, a second group of foil sections may have a second angle of attack based on a second, distinct tension in the through cable supporting the second foil section in the array. As such, a first portion of the modular foil system (e.g., the first group of foil sections) may generate a first lift, whereas a second portion of the modular foil system (e.g., the second group of foil section) may generate a second, distinct lift. This may allow, in some embodiments, the modular foil system to extend over a substantial span of the array, and generate specific or targeted lifts at particular areas of the array. And as described herein, the tension may be dynamically adjusted on-the-fly, and thus each portion of the modular foil system may be configured to compensate for dynamic conditions for an associated area within the array.

According to embodiments described herein, the foil systems, modular foil systems, and so on may be implemented with a marine array. A marine array may be towed through a marine environment by a vessel. In some embodiments, the marine array may be a seismic array. Broadly, a seismic array may include various sources and streamers used to study rock strata and other structures below the surface of the ocean or other bodies of water. One or more marine vessels are typically used to tow the source and/or receiver arrays in order to obtain relevant geological data covering a desired surface area of the ocean floor. For example, a single surface vessel may simultaneously tow both a source array and an array of seismic streamers, or different vessels can be used to tow separate source and receiver arrays. Alternatively, a towed source array can be used in conjunction with stationary receivers, for example, an array of ocean-bottom nodes, or with ocean-bottom cables deployed on the seabed.

It will be appreciated that a seismic array is one application of a marine array. In other embodiments, a marine array may be, or refer to, substantially any collection of components that are towed by a vessel through a body of water. As seen in the example ofFIG. 14, a marine array may include a fishing trawl1400that includes cables, nets, and/or other components configured to capture fish in the marine environment. The modular foil system of the present disclosure may be coupled with cables of the fishing trawl1400(e.g., upper cable1402and lower cables1404to widen the vertical opening of the trawl mouth, and port and starboard cables to widen the lateral opening of the trawl mouth) in order to facilitate its operation. This may include using the lift generated by the modular foil system to increase (or otherwise manipulate) a size of the mouth of the fishing trawl1400. One or more dynamic actuators may control one or more modular foil system attached to the cables1402,1404forming the mouth of the fishing trawl1400and steer the fishing trawl1400up or down and side to side. The modular foil systems can also be used to change the rate of descent and ascent of the trawl1400through the marine environment to increase or decrease deployment and retrieval times.

Other marine arrays are contemplated herein. In some cases, the marine array may be a towed payload used in a military application. As another example, the marine array may be a towed instrument or other payload used in oceanographic studies and the like. Accordingly, while the following figures may describe the modular foil systems in the context of a particular embodiment of a marine seismic array, this is for purposes of illustration. As such, any discussion of a modular foil system, foil section, and so on with respect to a particular embodiment of a marine array, may apply to other embodiments of marine arrays, and should not be construed as limiting.

Reference will now be made to the accompanying drawings, which assist in illustrating various features of the present disclosure. The following description is presented for purposes of illustration and description. Furthermore, the description is not intended to limit the inventive aspects to the forms disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art, are within the scope of the present inventive aspects.

One embodiment of a towed three-dimensional, high-resolution, marine seismic array100is depicted inFIGS. 1A and 1B. The array100is towed by a marine vessel102. A number of cables, ropes, or other lines may be attached to the marine vessel102. For example, an umbilical cable104with acoustic signal source generators (e.g., air guns) may trail directly behind the marine vessel102. A pair of tow ropes106or cables may splay out to port and starboard from the rear of the marine vessel102. A cross-cable108may extend between and connect to the tow ropes106adjacent to the aft ends of the tow ropes106. A number of streamer cables110may be connected to the cross-cable108at a number of locations along the length of the cross-cable108between the tow ropes106. In some embodiments, the streamer cables110may be evenly spaced apart from adjacent streamer cables110along the length of the cross-cable108. In a typical embodiment, there may be up to 18 streamer cables110and they may be spaced anywhere between 10 m and 100 m or more apart. Respective tail buoys111may be affixed to the ends of each of the streamer cables110which may help aid in maintaining a position of the streamer cables110, providing a visual marker for the array, and so on.

The cross-cable108may extend beyond the port-most and starboard-most streamer cables110to attach to the tow ropes106. These lateral sections of the cross-cable108may be referred to as spur lines114. In some embodiments, the spur lines114may be separate ropes or cables that connect to and extend between the lateral ends of the cross-cable108and the tow ropes106.

Paravanes112may further be attached to the tow ropes106at or adjacent to the connection between the tow ropes106and the spur lines114on each of the port and starboard sides. The paravanes112are winged hydrofoils that move outward in the water in an oblique direction to the direction of travel of the marine vessel102, thus providing lateral spread to the cross-cable106and the streamer cables110attached thereto. In other configurations, alternative spreading devices may be employed to maintain separation of the streamer cables110, including foil wings as described in U.S. Patent Application Publication No. US20170299747A1.

A signal cable116may extend from the marine vessel102on one side of the array100to connect to the cross-cable108and return signals received by the sensors111on the streamer cables110. On an opposite side of the array100, a recovery rope118may extend from the marine vessel102and connect with the cross-cable108adjacent to the last streamer110. Surface floats117may be attached to the cross-cable108at or adjacent to the lateral ends thereof via a cable with a length corresponding to a desired depth of the streamer cables110. The surface floats117act to ensure that the cross-cable108, and thus the streamer cables110, do not submerge too deeply when the array100is towed.

Unfortunately, the port and starboard ends of the cross-cable108, and thus the streamer cables110attached thereto, may not achieve a desired depth beneath the surface due to the pull of the paravanes112on the spur lines114. The paravanes118remain at the surface of the water and thus pull the lateral ends of the cross-cable upward as well as laterally outward.

To counteract the effect of the paravanes212on the cross cable208, a positioning device or depressor220designed to provide downward lift may be attached to the cross-cable208, the spur line214, or both, as shown inFIG. 2. The depressor220may be composed of a number of foils222pivotably attached to the cross-cable208or the spur line214. The collection of foils222forming depressor220are referred to herein as a “modular foil depressor.” As shown inFIG. 2, the modular foil depressors220may fill the entire length of the spur line214. Alternatively, the modular foil depressor220may only fill a portion of the spur line214and may be situated either laterally outward closer to the paravanes212or more inward closer to the streamer cables210. As noted above, the modular foil depressor220may also be positioned on the cross-cable208, inside the port-most and starboard-most streamer cables210. The location of the modular foil depressor220may be selected based upon a number of factors including the amount of downward lift generated by the modular foil depressor220, the separation distance of the streamer cables210, the mass of the sensors211, streamer cables210, and cross-cable208, and the lift force generated by the paravanes212among other factors.

In addition to the depth control discussed, as shown inFIG. 3, a modular foil depressor320deployed on the spur line314also provides “lift assist” to the paravanes312attached by a bridle313to the intersection of the tow lines304and spur lines314. That is, since the modular foil depressor320induces a downward catenary to the spur line314, as shown inFIG. 3, a first component362of the lift force360acts downward as discussed above, but a second component364of the lift force360also acts horizontally (i.e. outboard). This horizontal “lift assist” of the second component364provided by the modular foil depressor320means that the existing standard paravanes312will now be able to spread the seismic array300wider than previously possible. Alternatively, the configuration including the modular foil depressor320on the spur line314may achieve the same spread but at a shorter offset behind the marine vessel towing the array300. In another implementation, the same spread and offset may be achieved, but a more efficient setting for the bridle313attaching the paravanes312may be used and hence reduce fuel consumption of the marine vessel.

In addition to the use of a series of depressor sections on spur lines to achieve depression forces to submerge streamer heads down to desired depths for seismic arrays, the modular foil depressor may provide a number of other features and advantages.

The modular foil depressor can readily be installed on existing in-water equipment, such as, for example, by threading the individual depressor sections onto existing spur lines between paravanes and outboard streamer cable heads. Modular foil depressors may also be installed on numerous other existing ropes.

The modular foil depressor can be deployed over the side of the marine vessel, or down the gun chute, and will then self-orient and generate lift without operator intervention. Handling, deployment, and recovery operations are essentially hands-free with no special davits or dedicated winches or cranes required. It is also compact and can be easily and efficiently stowed on the vessel when onboard.

In other embodiments, a foil system may be used to generate a lift along a lateral direction. This may allow a foil system to steer or position a component of the marine array. For purposes of illustration, a schematic illustration of a dynamic wing foil system420, composed of a number of adjacent foil sections430, is shown inFIG. 4. The dynamic wing foil system420may generally extend perpendicularly into a marine environment and generate lift that is used to steer components of the array.

To facilitate the foregoing, the dynamic wing foil system420is shown inFIG. 4as including a representative the adjustment mechanism450. The adjustment mechanism450may include various components that may be used to manipulate the wing foil system420, such as manipulate an orientation of the wing foil system420to generate a target lift when towed through the marine environment. In an embodiment, the adjustment mechanism may include a turnbuckle452and a pulley454, ratchet, winch, or similar cable guide and feed mechanism may be mounted to the floatation apparatus418, e.g., between a control cable438and an aft anchor point458on the back or rear section of the floatation apparatus418(in the trailing edge direction of the foil sections430). The forward cable436and through cable434extending through the foil sections430are mounted to a forward anchor456attached to the front section of the floatation apparatus418(in the leading edge direction of the foil sections430).

The adjustment mechanism450can be configured for adjusting either the forward cable436or the aft cable438; both embodiments are encompassed. Another option is to use an adjustment mechanism450that provides differential adjustments to both forward and aft cabled436,438; e.g., by shortening one cable while lengthening the other at the same time. In some designs a single control cable may be used, extending from the forward cable anchor456down along a forward cable section436, then passing through a cable return or wrapping or inflecting around a cable connector429attached to a submerged cable444, and back up along an aft cable section438to the forward anchor458through the pulley454. Alternatively, separate forward and aft control cables436,438may be provided, e.g., individually attached at the submerged cable connector429. The submerged cable444can be provided either as a tow line for a streamer cable448or as an umbilical for a source gun array.

A control device459for the adjustment mechanism450may be located at either the top or bottom end of the foil wing system420, for example, inside the floatation apparatus418. Suitable control devices459include processor, memory, and software components configured to direct the adjustment mechanism450to selectively vary the length and/or tension in the forward and aft cables436,438, in order to regulate the lift and steering forces generated by the foil wing system420by changing the angle of attack along individual foil sections430. For example, the control device459may be configured to control an electric motor or similar drive in order to actuate the adjustment mechanism450, providing for automated steering by adjustment of the relative length and tension in the forward and aft control cables436,438. Other control options include, but are not limited to, hydraulic and pneumatically controlled ram or piston mechanisms, electric winch drives, and motor-driven rack and pinion arrangements. For example, in some cases, control systems and configurations such as those described in U.S. Patent Application Publication No. US20170106946A1 may be employed to facilitate tensioning of the cables described with respect toFIG. 4.

In the context of a seismic survey as described above, a number of seismic energy source devices and/or a number of sensor nodes may be attached along the length of cables deployed and towed behind the marine vessel. Each of the cables, or the seismic equipment attached to the cables, may have a steering device associated therewith in order to adjust the position of the cable or seismic devices within the water. In some implementations, it may be very important that the towed marine equipment such as the cables with seismic equipment closely follow a predetermined course (e.g., in order to accurately map a subsurface formation). In addition, if multiple cables are deployed behind a marine vessel it may be important to maintain a constant separation distance between the cables. To meet these needs, steering mechanisms may be attached to each cable and further or alternatively attached to the equipment towed by the cable.

The foil wing systems420are just one exemplary implementation of a steering mechanism that may be employed to steer and position cables, seismic energy sources, sensor nodes, buoys and floats in the seismic array, etc. Other steering mechanisms for attachment to such sensor array components exist. These may include paravanes, hydrofoils, rudders, wings, elevators, and various other devices. The orientations of each of these devices while being towed through the water may be adjusted for steering. Such adjustments may be made by increasing or decreasing tension on control cables (i.e., making them more taught or more slack), engaging actuators to physically move a steering element; engaging motors to drive rotating elements, etc. In each case, the steering mechanisms are controlled by signals calculated to alter their orientation appropriately to maintain a proper course for the seismic array elements within the water. These signals are determined by sophisticated navigation and control systems that work in concert with the navigation of the marine vessel in order to ensure that the elements of the seismic array stay on course and maintain proper separation distances between adjacent elements.

FIGS. 5A-7depict embodiments of foil systems of the present disclosure. In particular,FIGS. 5A-7depict embodiments of foil systems that define a group foil shape configured to have an adjustable angle of attack or orientation. In this regard, the foil system or systems of the present disclosure may generate a variety of distinct lifts based on the adjustable angle of attack of the group foil shape. It will be appreciated that that foil systems and configurations described with respect toFIGS. 5A-7may be used with any of the marine arrays described herein. In this regard, the foil systems described with respect toFIGS. 5A-7may be used as, or define a component or assembly of, a modular foil depressor (e.g., depressor220ofFIG. 2), a wing foil system (e.g., wing foil system420ofFIG. 4), and so forth as may be appropriate for a given application.

With reference toFIG. 5A, a tensioned cable580is shown. The tensioned cable580may be any appropriate cable of a marine array, such as a cable that is in tension and forming a component of a seismic array or fishing trawl assembly, among other applications. The tensioned cable580is shown towed along a direction of tow590. At a first end, the tensioned cable may be tensioned in a first tensioning direction582a. At a second end, opposite the first end, the tensioned cable may be tensioned in a second tensioning direction582b.

FIG. 5Afurther shows a foil system500, which is further depicted in different variations of deployment inFIGS. 5B-5F. The foil system500may be coupled with, or substantially replace, the tensioned cable580. This may allow the foil system to provide lift to the portion of the marine array associated with the tensioned cable580. The foil system500may include a number of foil sections504. Each foil section504has a span, a chord, and a foil cross-section, which may be a standard hydrofoil cross-section, as shown and described further herein with respect toFIGS. 8A and 8B, or may be any other desired foil cross-section, such as NACA, Eppler, Gottingen, or any other custom foil cross-section suitable for the desired application.

The foil sections504may be arranged or stacked adjacent one another. In this regard, the foil sections504may be a group of foil sections that collectively define a foil shape. The foil shape may have a leading edge512and a trailing edge508. The foil shape of the foil system500may be arranged at a variety of orientations or angles of attack relative to a direction of a flow, for example, as described in greater detail below with respect toFIGS. 6A and 6B. This may cause the foil system500to generate lift that is used to manipulate components of a marine array (e.g., seismic cables, receivers, and so on) in order to steer, move, position, and/or depress the components, as may be appropriate for a given application.

In the embodiments ofFIGS. 5A-5F, the foil sections504are coupled to one another using a pair of through cables, such as a first through cable526aand a second through cable526b. The first through cable526aand the second through cable526bmay extend through the foil sections504, thereby supporting the foil sections504within the foil system500. As one example, the foil sections504may define ducts that extend through the foil sections504. The ducts may extend along and just aft of each of the leading edge512and just forward of the trailing edge508of the foil shape. The first through cable526aand the second through cable526bmay therefore be positioned within and threaded through the ducts of the foil section504. In turn, the first through cable526aand the second through cable526bmay be coupled to another component or assembly of a marine array, and thereby help support the foil sections504with the array.

In the embodiment ofFIGS. 5A-5F, the first through cable526aand the second through cable526bmay couple the foil sections504to connection points within a marine array. In a particular embodiment,FIG. 5Ashows a first connection point550and a second connection point552. The first connection point550and/or the second connection point552may be a hook, a tie, a pulley, a fixed connection, and so on of the marine array; however, other configurations are possible. The connection points550,552may generally define a module of a modular foil system (e.g., such as that described in greater detail with respect toFIG. 7) and, as such, other groups of foil sections504may be connected to one another at the connection points550,552.

Each of the connection points550,552may be coupled with distinct connection cables. This may allow the foil system to be coupled to substantially any other cable, rope, assembly and so on of the marine array, including components of seismic array, a fishing trawl, and so on. For example,FIG. 5Ashows a first connection cable554aand a second connection cable554bthat are coupled to respective ones of the connection points550,552. In turn, the first connection cable554aand the second connection cable554bmay be coupled to other components of the marine array, according to embodiment described herein.

In the embodiment shown inFIGS. 5A-5F, the through cables may converge at the connection points adjacent opposing ends of the foil sections. For example, the first through cable526aand the second through cable526bmay converge toward the first connection550. Also, the first through cable526aand the second through cable526bmay converge toward the second connection552. This may allow for more precise or accurate control of an orientation of the foil sections.

For example, the first through cable526amay extend from the first connection point550to the second connection point552. Between the first connection point550and the second connection point552, the first through cable524amay extend through a duct of the foil sections504(e.g., a duct defined along and just aft of the leading edge512). The second through cable526bmay extend from the second connection point550to the second connection point552. Between the first connection point550and the second connection point552, the second through cable526bmay extend through a duct of the foil sections504(e.g., a duct defined along and just forward of the trailing edge508).

Accordingly, a position or orientation of each foil section504may be defined (or constrained by) the through cables526a,526b. For example, each foil section504may be subjected to dynamic hydrodynamic forces and thus move relative to one another. When the through cables526a,526bare substantially slack or otherwise permit movement between each of the foil sections504, each foil section504may migrate apart from one another. However, by applying tension in one or both of the cables526a,526b, the cables526a,526bmay form a triangular shape that may act to constrain the movement of foil sections504relative to one another. The increased tension may also help each foil section504to stack adjacent to one another, for example, in order to define the foil shape having the leading edge512and the trailing edge508. In some cases, one or both of the cables526a,526bmay be tensioned in order to define a catenary of the foil shape.

In certain embodiments, the tension may be increased in one or both of the through cables526a,526bin order to adjust an angle of attack of the foil shape. As one possibility, a tension in one or both of the through cables526a,526bmay be increased, which, in turn, may increase an angle of attack of the foil shape defined by the foil sections504. The increased angle of attack may generally cause the foil system500to generate additional lift. As such, the tension of one or both of the through cables526a,526b(or any other cables or ropes supporting the foil sections504within the array) may be adjusted in order to manipulate lift generated by the foil system500.

To facilitate the foregoing,FIGS. 5B-5Fdepict embodiments in which the first and second through cables524a,524bconverge at the connection points550,552, which are adjacent opposing ends of the foil system500. Converging the through cables524a,524btoward common connection points550,552, may allow an actuator to control the tension in one or both of the through cables524a,524bin a precise, accurate, and potentially dynamic manner.

With particular reference toFIG. 5B, the tensioned cable580is arranged substantially parallel to, and connected with, the foil sections504. In this regard, the foil system may be “piggy-backed” onto an existing high-tensioned cable (e.g., tensioned cable580) for installation into a marine array, including any of the seismic arrays, fishing trawls, military vessels, and so on, described herein.

For example, the tensioned cable580may be a cable of a marine array and the foil system500may be coupled with the tensioned cable580to provide lift at a target region of the array. As shown inFIG. 5B, the first connection cable554amay be coupled with the tensioned cable580at a first end. Further, the second connection cable554bmay be coupled with the tensioned cable580at a second end. In this manner, the foil sections504may generate lift, as described herein, that in turn lifts the tensioned cable580in a specified manner. Lift may therefore be delivered to a particular region of the marine array by attaching the foil system500to existing structures and components of the array, rather than modifying components of the array to accommodate the foil system.

With reference toFIG. 5C, another embodiment of the foil system500is shown in which the foil system500includes an actuator524. The actuator524may be used to adjust a tension in one or both of the first through cable526aor the second through cable526b, which, in turn, may adjust an angle of attack of a foil shape defined by the foil section504. The actuator524is shown inFIG. 5Cas coupled to or positioned on the first through cable524aat a first end516of the foil system500. Positioning the actuator524on the first through cable526amay help orientate the leading edge512in one or more directions in order to generate a target lift for the foil system500. In other cases, actuators may be arranged at various other positions of the foil system500, including being positioned on the second through cable524b, for example, as shown with another actuator524′ (shown in phantom).

The actuator524, may be substantially any appropriate component that is used to adjust a tension in a cable. For example, the actuator may be a mechanical component, such as a turnbuckle. The turnbuckle may be manually adjusted, for example, prior to deployment of the array, in order to set a desired angle of attack of the foils. Additionally or alternatively, the foil system may include various dynamic actuators, such as a pneumatic or electromechanical controller that is used to modify a tension in the pair of through cables, for example, as described in U.S. Patent Application Publication No. 20170106946A1. It will be appreciated, however, that other actuators are possible and contemplated with the scope of the present disclosure.

In some cases, the actuator may be configured to adjust a tension of the cable while the array is deployed in a marine environment. For example, the actuator may be configured to receive a signal from another source, such as a vessel towing the array, or another remote source. The actuator may use the signal to adjust a tension in the cable. For example, in a first configuration, the signal may be indicative of a first desired orientation and the actuator may adjust a tension in the through cable in order for the foil section to match the first desired orientation. Likewise, in another configuration, the signal may be indicative of a second desired orientation and the actuator may adjust a tension in the through cable in order for the foil section to match the second desired orientation. In this regard, the actuator524may, more broadly, be a component of the adjustment mechanism (e.g., adjustment mechanism450ofFIG. 4) or other steering or positioning system described herein.

With reference toFIG. 5D, another embodiment of the foil system500is shown. In the embodiment ofFIG. 5D, the actuator524is shown connected to the second connection cable554b. It will be appreciated that the second connection cable554bis a continuation of one of the first or second through cables526a,526b. By connecting the actuator524to the second connection cable554b, the actuator524may be positioned outside of the triangle formed by the first and second through cables526a,526b. By positioning the actuator outside of the triangle formed by the through cables526a,526b, an angle of attack of the foil section504may be manipulated in a controlled manner, in certain embodiments. For example, in the embodiment ofFIG. 5D, the actuator524functions as an external tensioning member and therefore operates to control an angle of attack of the foil section504in a manner that is different from that of the internal tension member configuration described herein.

To facilitate the foregoing,FIGS. 5E and 5Fprovide further implementation details of the system shown inFIG. 5D. For example,FIG. 5Eshows the foil system500having the external tension member described with respect toFIG. 5Dhaving three anchor points. By way of illustration, a first anchor point594is positioned adjacent to a first end520of the foil system500. A second anchor point596and a third anchor point598are positioned adjacent to a second end516of the foil system500. Each of the anchor points may represent a region or point of a marine array that is “fixed” with respect to the foil system500, for example, such that movement of the cable or other associated component is constrained. At the first end520, the foil system500may be connected to the first anchor point594by cable554a. And at the second end516, the foil system500may be connected to the second anchor point596by cable554band to the third anchor point598by another connecting cable556.

The second anchor point596and the third anchor point598may help arrange the actuator524within the foil system500. For example, the actuator524may be positioned substantially between the second anchor point596and the third anchor point598. This may allow the actuator to be connected with one of the through cables526a,526band define an external tensioning member for the foil system500.

In the embodiment ofFIG. 5E, the actuator524is connected with the first through cable526a. As shown in the detail ofFIG. 5E, the first through cable526aand the second through cable526bmay each converge toward a connection point defined at the second anchor point596. At the second anchor point596, a ring552′ may be positioned for engaging each of the first through cable526aand the second through cable526b. In the embodiment ofFIG. 5E, the second through cable526bmay terminate or be tied off at the ring552′. The first through cable526a, however, may be engaged with the ring552′, such as extending through the ring552′ and continue beyond the second anchor point596for connection with the actuator524. As shown inFIG. 5E, a connection cable554bmay connect the actuator524to the third anchor point596.

FIG. 5Fshows another example implementation of the actuator524as an external tension member. For example,FIG. 5Fshows the foil system500having an external tensioning member described with respect toFIG. 5Dand having two anchor points. In this regard, the embodiment of the foil system500ofFIG. 5Fmay be substantially analogous as that shown with respect toFIG. 5E. Notwithstanding, as shown in the detail ofFIG. 5F, the ring552′ may be uncoupled with a fixed connection, such as the second anchor point596ofFIG. 5E. In this regard, a connection cable528may be employed in order to connect the ring552′ to the actuator524and stabilize a position of the ring552′ along the first through cable526a.

FIGS. 6A and 6Bdepict a perspective view of foil system600. The foil system600may be substantially analogous to any of the foil systems described herein, such as the foil system500ofFIG. 5. In this regard, the foil system600may be configured to generate lift in a marine environment and may include: foil sections604, a leading edge608, a trailing edge612, a first through cable642, a second through cable644, a connection point646, and an actuator624. Redundant explanation of such components is omitted here for clarity.

FIGS. 6A and 6Balso depict the foil section600having a first duct632and a second duct634. The first through cables642may be positioned within and threaded through the first duct632, and the second through cable644may be positioned within and threaded through the second duct634. As shown inFIGS. 6A and 6B, the first through cable642and the second through cable644may converge toward the connection point646. This may facilitate adjusting a tension in one or both of first through cable642,644, as described herein. Extending from the connection point may be an attachment cable648. The attachment cable648may be a component or assembly of a marine array, such as the seismic arrays described herein. In other cases, such as that described with respect toFIG. 7, the cable648may be a connection to, or be used to connect, the foil system600with other foil systems in order to form a modular foil system.

FIGS. 6A and 6Bdepict the foil system600in embodiments in which an angle of attack (a) of the foil system600is adjustable and may be adjusted. For example, as described herein, a tension in one or both of the through cables of642,644may be adjusted by the actuator624. The adjustment in tension may cause the foil section604to alter an angle of attack relative to a flow F.

FIGS. 6A and 6Balso depict a change in a triangular shape formed by the through cables642,644, and an end of the foil section604adjacent the connection point646. As described herein, the triangular shape may change according to a magnitude of tension in one or both of the through cables642,644. In the examples shown inFIGS. 6A and 6B, the actuator624is associated with the first through cable642. In a neutral or unactuated state, the first through cable642may form a substantially ninety degree angle (e.g.,0) with the end of the foil section604, and thus the triangular shape may resemble a right triangle. As the actuator624operates to decrease tension exhibited by the first through cable642, the triangular shape may change, for example, such as by representing an isosceles triangle. As is evidenced by the changing form of the triangular shape, an angle of attack of the foil system600may be modified without reliance on, or substantially unhindered by, adjacent foil systems or other components of the seismic array, and so on.

With reference toFIG. 6A, the foil system600is shown at a first angle of attack α. For example, the actuator624may adjust the tension in one or both of the first through cable642or the second through cable644. The adjustment may be an increase in tension, for example, from a slack or equilibrium tension, which in turn causes individual foil sections604to orientate at the angle α from the direction of the flow F.

When arranged at the first angle of attack α, the foil system600may generate a first lift. For example, the foil sections604may be a standard NACA or other foil shape, as described herein, and as such, when orientated at the angle of attack α, the foil sections604may generate the first lift. The first lift may be a lift that is targeted to steer, position, and/or otherwise maintain or manipulate components or assemblies of a marine array. In this regard, the actuator624may be coupled with either the first through cable642or the second through cable644, and adjust the tension in one or both of the first through cable642, or the second through cable644such that the foil system600generates the required lift.

As shown inFIG. 6A, when the foil system600is arranged at the first angle of attack α, the first through cable642may generally form an angle θ with the adjacent end of the foil section604. While the angle θ is shown inFIG. 6Aas being substantially ninety degrees, it will be appreciated that angles of various magnitudes are possible, for example, based on a tension in the first through cable642.

Accordingly, the actuator624may be a dynamic actuator that is configured to adjust the tension in one or both of the first through cable642and the second through cable644in response to a signal. The signal may be from another source, such as a vessel, that causes the actuator624to adjust the tension in one or both of the through cables642,644to a certain value. Additionally or alternatively, the actuator624may be responsive to dynamic conditions and operate to facilitate maintenance of the foil system600along a desired course or position. For example, various sensors may be integrated with the foil system600, including within the foil sections604, and output various data such as position and speed of the foil system in addition to information concerning, for example, a marine environment, such as pressure, temperature, currents, and so forth. Such data from sensors incorporated with the foil system600may be used by the actuator624(or other associated system) in order to manipulate the foil system600. To illustrate, such sensors may detect that the foil system600is undesirably positioned within a marine array (e.g., due to unanticipated hydrodynamic forces). In turn, a processing element, controller, and so forth (local and/or remote) may determine a new target lift for the foil system600to generate in order to obtain its desirable position. The actuator624may receive information regarding the new target lift and adjust the tension in one or both of the through cables accordingly.

In this regard, with reference toFIG. 6B, the foil system600is shown at a second angle of attack α′. At the second angle of attack α′, the foil system600may generate a second lift. The second lift may be the new target lift, for example, described above with respect to the operation of the actuator624inFIG. 6A. In other cases, the second lift may be desired or predetermined lift for the marine array.

To facilitate the foregoing, the actuator624may be coupled with either the first through cable642or the second through cable644, and adjust the tension in one or both of the first through cable642or the second through cable644. The adjustment may be an increase in tension, for example, from a tension of the cables ofFIG. 6A. In turn, this may cause individual foil sections to orientate at a greater angle relative to the flow F than that shown above with respect toFIG. 6A. Accordingly, the second lift may be greater than the first lift, and thus used to steer, position, and/or otherwise maintain or manipulate components or assemblies of a marine array in a manner distinct from the first lift.

As shown inFIG. 6B, when the foil system600is arranged at the second angle of attack α′, the first through cable642may generally form an angle θ′ with the adjacent end of the foil section604. While the angle θ′ is shown inFIG. 6Bas being an acute angle, it will be appreciated that angles of various magnitudes are possible, for example, based on a tension in the first through cable642.

As described above with respect toFIG. 6A, the actuator624may be a dynamic actuator or otherwise configured to adjust a tension in one or both of the first through cable642or second through cable644when the foil system600is submerged or deployed in the marine array. Accordingly, while the actuator624is described above as increasing a tension in the first through cable642or second through cable644, it will be appreciated that the actuator624may decrease a tension in the cables. For example, the actuator624may decrease a tension in one or both of the first through cable642or the second through cable644in order to decrease a magnitude of the angle of the attack. This may be desirable in order to decrease lift generated by the foil system600. As such, rather than binary configurations,FIGS. 6A and 6Bshow two possible angles of attack along a spectrum of possibilities. The tension in the through cables is varied in order to modify the angle of attack to generate a target lift, and as such, the tension may be varied in any appropriate manner in order to achieve a desired positioning or other manipulation of marine array components using the lift generated by the foil system600.

The foil systems described herein may be used to define modules of a modular foil system, such as the modular foil system700described with respect toFIG. 7. For example, groups of foil sections may be “daisy-chained” or otherwise linked to one another in order to create a modular foil system. Each group of foil sections may be tunable in order to generate a particular lift that may be different than other groups of foil sections of the modular foil system. This construction may enhance the adaptability and precision of the system. For example, as described herein, each group of foil sections may be supported within the modular foil system by through cables and the tension may be distinctly controlled for each respective group of foil sections. In this manner, not only may each group of foil sections (module) have a distinct tension (and therefore distinct angle of attack), the through cables may be more responsive to actuators configured to adjust the tension, for at least because the tension is adjusted over a shorter, more isolated span of cable. The daisy-chaining or linking of the groups of foil sections may allow the modular foil system to generate lift over a larger span within the marine array, thereby enhancing the possibilities for array designs that implement foil systems over a large span.

To illustrate the foregoing,FIG. 7depicts the modular foil system700. The modular foil system700may include modules that are daisy-chained or linked to one another in order to form the modular foil system700. In the example ofFIG. 7, the modular foil system700includes a first module700a, a second module700b, and a third modular700c; however in other embodiments, more or fewer modules may be used. Broadly each of the modules700a,700b,700cmay include a group of foil sections, such as any of the foil sections described herein, that cooperate to form a foil shape and generate lift. In this regard, each of the modules700a,700b,700cmay be configured to have an angle of attack with respect to a direction of flow. The angle of attack for each of the module700a,700b,700cmay be adjustable. This may allow each module700a,700b,700cto have a distinct angle of attack, and subsequently generate a distinct lift. This may allow the modular foil system700to tune the lift generated along specific regions of the system, for example such as increasing the lift generated at a first or second end, without necessarily adjusting the lift in other or adjacent regions of the system. As such, the modular foil system700may more precisely control lift generation along its entire length or span, and also allow for differential lift generation, which may be appropriate, for example, where distinct components or assemblies of the marine array (having different lift or positioning requirements) are attached along different region of the system700.

It will be appreciated that each of the modules700a,700b,700cmay include components substantially analogous to the component described herein with respect to various other foil systems, such as the foil system500and the foil system600ofFIGS. 5 and 6, 6B, respectively. For purposes of illustration, the module700ais shown as having foil sections704, a leading edge708, a trailing edge712, a first pair of through cables726a,726b, an actuator724, and a connection746; redundant explanation of such components is omitted here for clarity. Accordingly, the modules700band700cmay also include such components, such as a second pair of through cables752a,752b, and associated functionality; however, this is not required.

The modules700a,700b,700cmay be daisy-chained or linked to one another, in part, due to the convergence of through cables (that support the groups of foil section) toward connection points. For example, a connection point (e.g., connection point746) may be a ring, a knot, a pulley, or other point situated between adjacent groups of foil sections. The adjacent groups of foil sections may be connected to one another using the connection point.

In the example ofFIG. 7, the modular foil system700includes the first pair of through cables726a,726bthat supports the foil sections of the module700a. The modular foil system700also includes the second pair of through cables752a,752bthat supports the foil sections of the module700b. The first pair of through cables726a,726bmay converge toward the connection point746. This may allow the module700ato attach to a discrete assembly of the marine array at the connection point726. For example, the discrete assembly may be the second module700b, as shown inFIG. 7. As such, the second pair of through cables752a,752bmay also converge toward the connection point746. As described herein, because each of the first pair of through cables726a,726band the second pair of through cables752a,752bconverge toward the connection point746, foils of the module700amay articulate relative to foils of the module700b.

Despite being connected to one another using the connection point746, the first module700amay move (or pivot) generally independent from the adjacent module700b. Further, the connection point746may provide a demarcation between the first pair of through cables726a,726band the second pair of through cables752a,752b, thereby allowing for each of the modules700a,700bto have distinct tensions. For example, an actuator associated with the first module700amay be configured to alter a tension in one or both of the pair of through cables726a,726b, and an actuator associated with second module700bmay be configured to alter a tension in one or both of the second pair of through cables752a,752bgenerally independent of the actuator associated with the first module700a. As described herein, the adjustment of tension in the through cables may influence an angle of attack of the foil sections, and hence the lift generated. Accordingly, because the tension in the first pair of through cables726a,726bmay be adjusted independent of an adjustment in tension of the second pair of through cables752a,752b, an angle of attack (and generated lift) may also be different in each respective module of system700.

It will be appreciated that the adjustable angle of attack of the modules700a,700bis shown and described for purposes of illustration. As shown inFIG. 7, the modular foil system700also includes the third module700c, which may also have an adjustable angle of attack, for example, substantially analogous to that described with respect to the modules700a,700b. In yet other case, the modular foil system700may have a fourth, fifth, sixth, seventh, or any appropriate number of modules, each linked to one another. In such cases, some or all of the individual modules may also have an adjustable angle of attack.

An exemplary form of a single foil section822of a modular wing foil system is depicted inFIGS. 8A and 8B. The foil section822is scalable to suit a wide range of lift requirements, while also offering very high aspect ratios. The foil section822has a body830with a foil shape having a leading edge832and a trailing edge834. The line connecting the leading edge832and the trailing edge834passing through the mid-thickness of the body830is referred to as the “chord line” of the foil shape. When viewed from a top plan perspective, the foil section822may appear rectangular in shape. A first surface836extends between the leading edge832and the trailing edge834and may be cambered. A second surface838of the body830extends between the leading edge832and the trailing edge834and may be relatively flat with respect to the first surface836.

The body830has two lateral sides842,844that extend between the lateral edges of the first surface836the second surface838and between the leading edge832and the trailing edge834. The body830may be made from solid cast polyurethane for near-neutral buoyancy and high abrasion resistance and durability. However, the body830may still be slightly negatively buoyant, such that the body830will influence the equilibrium angle of attack, especially at low tow speeds. Thus, the downforce achieved by the foil section822may be influenced by selecting the composition of the body830.

A first tubular conduit846may be defined within the body830and extend laterally through the body830adjacent to the leading edge832and open to each of the first and second lateral sides842,844. The first tubular conduit846is sized to receive ropes or cables (such as separation ropes and/or spur lines) of a seismic array therethrough.

A second tubular conduit852may be defined within the body830forward of the trailing edge834and extend laterally therein parallel to the first tubular conduit846and open to each of the first and second lateral sides842,844. The first tubular conduit846may be positioned within the aft 50 percent of the of the cord length of the foil section822. The second tubular conduit852may be similarly sized to receive a rope or cable therethrough.

The number of foil sections822in a modular foil depressor120or a wing foil system420is scalable to suit a wide range of lift requirements, while also offering very high aspect ratios. In some cases, this can avoid the need for a supplementary ballast. In other cases, supplementary ballast can be desirable, and integrated with one or more foil sections of the present disclosure, such as those shown below with reference toFIGS. 9-11. The foil sections822may rotate in a flow field. The angle of attack at which the modular foil depressor120or wing foil system420can achieve equilibrium will be a function of the moment coefficient of the particular cross-section of the foil822being used, and the comparative tensions established in the forward through cable642versus the aft through cable644. When the aft through cable is completely slack, the center of rotation for the foil section822will be the forward through hole846. As the tension balance changes between the forward through cable642and the aft through cable644, the center of rotation is transferred to the aft through hole852, at which point the forward through cable642acts to prevent further rotation of the foil822about its center of rotation, thereby setting the new equilibrium angle of attack.

Consequently, the magnitude of downforce generated by a modular foil depressor120or outward force generated by a wing foil system420formed by foil sections822can be controlled by various factors including the following:Adjusting the overall span of the modular foil depressor120or wing foil system420(i.e. the number of depressor sections822threaded onto the rope or rod);Varying the length of the chord of the foil sections822(i.e. customize the size of the foil sections822at time of manufacture to suit the required end application); andChoice of camber for the foil profile of the foil sections822(lesser or greater cambered foil depressor sections822generate lower or higher lift coefficients).

The second rope or cable threaded through the second tubular conduit852in the foil sections822of the modular foil depressor120or wing foil system420allows for adjustment of the lift by controlling the catenary (billow) of the modular foil depressor120wing foil system420. The pair of ropes may be adjusted in length to effect controllable adjustments in lift. The equilibrium angle of attack achieved is a function of the relative lengths of the dual ropes. For example, if the aft rope passing through the second tubular conduit852in the aft half of the foil sections822is shortened with respect to the rope passing through the first tubular conduit846, the trailing edges834of the depressor sections822will be pushed closer together laterally as compared to spacing between the foil sections822at the leading edges832. This causes the modular foil depressor120or wing foil system420to billow and change the angle of attack along the length of the modular foil depressor120or wing foil system420.

The modular foil depressor offers high aspect ratios and high lift-to-drag efficiency. The modular foil depressor offers a high degree of flexibility in terms of the number of choices available, including pivot location, camber, chord length, and tail fin size and angle, to selectively adjust the downforce to suit operational requirements and specifications. Lift is also adjustable by adjusting the tension in the cables running through the foils.

The modular foils of the present disclosure can also be adapted to receive a ballast material and/or to add buoyance to the foil. For example, in particular applications, it can be desirable to selectively increase a weight in the foil section. This can enhance the stability of the foil and/or facilitate orientating the foil in a particular configuration. Additionally or alternatively, it can be desirable to add pockets to the foil section that operate to enhance the buoyance of the foil section. In some cases, the same structure of the foil section can be used to facilitate buoyancy enhancement and ballast adding. For example, a pocket, tube, channel, or the like can be formed in the foil section. This pocket or other like structure can define an enhanced buoyance portion of the foil section. The pocket can also be adapted to receive a ballast material, based on the desired application.

FIGS. 9-11show example cross-sections of a foil section that can include a buoyancy pocket and/or be adapted to receive ballast material. It will be appreciated that the foil sections show inFIGS. 9-11can be used with any of modular foil system described herein. For example, the modular foil systems of the present disclosure can include a plurality of foil sections, and some or all of the plurality of foil sections can include a foil section adapted to include a buoyance pocket and/or to receive a ballast material. In some cases, this can include a combination of foil sections, some of which have a buoyance pocket and/or ballast materials, along with other foil sections that do not necessarily include such features. The example geometries of foil sections ofFIGS. 9-11are therefore presented for purposes of illustration; in other embodiments, other geometries are contemplated herein.

With reference toFIG. 9, a foil section922is shown. The foil section922can be substantially analogous to the foil section822described above, and as such include similar components and/or perform similar functions. In this regard, the foil section922includes a leading edge932, a trailing edge934, a first surface936, a second surface938, a first tubular conduit946, and a second tubular conduit952.FIG. 9also shows the foil section including a first pocket970and a second pocket972. The first and second pockets970,972can be features formed into a body of the foil section922. For example, the first and second pockets970,972can be channels, bores, through-portions, or other like features that extend through some or all of a cross-dimension of the foil section922. The first and second pockets970,972can be adapted to define a buoyancy-enhanced portion of the foil section922, such as may be the case where the pockets970,972are filled with a material having a less density of the fluid within which the foil section922is immersed or partially immersed. In other cases, the first and second pockets970,972can be adapted to receive a ballast material. The ballast material can generally have a density that is similar to or greater than a density of the fluid within which the foil section is immersed or partially immersed.

With reference toFIG. 10, a foil section1022is shown. The foil section1022can be substantially analogous to the foil section1022described above, and as such include similar components and/or perform similar functions. In this regard, the foil section1022includes a leading edge1032, a trailing edge1034, a first surface1036, a second surface1038, a first tubular conduit1046, and a second tubular conduit1052.FIG. 10also shows the foil section1022as including a first pocket1070, a second pocket1072, and a third pocket1074. The pockets1070,1072,1074can be substantially analogous to the pockets970,972described above in relation toFIG. 9. Notwithstanding, the pockets1070,1072,1074can have a different geometry and arrangement on the foil section1022. For example, as shown inFIG. 10, the first and second pockets1070,1072are arranged generally between the first and second tubular conduits1046,1052, and the third pocket1074is arranged generally between the second tubular conduit1052and the trailing edge1034. The pockets1070,1072,1074can generally assume a larger cross-sectional area of the foil section than that of the pockets ofFIG. 9, and thus can be adapted to provide enhanced buoyance or ballast as may be appropriate for a given application.

With reference toFIG. 11, a foil section1122is shown. The foil section1122can be substantially analogous to the foil section1122described above, and as such include similar components and/or perform similar functions. In this regard, the foil section1122includes a leading edge1132, a trailing edge1134, a first surface1136, a second surface1138, a first tubular conduit1146, and a second tubular conduit1152. A third tubular conduit1148and a fourth tubular conduit1149are also shown, which may be adapted to receive one or ropes or cables, as described herein in relation to other forward-most conduits of the foil sections described herein.FIG. 11also shows the foil section1122as including a first pocket1170and a second pocket1172. The pockets1170,1172can be substantially analogous to the pockets970,972described above in relation toFIG. 9. Notwithstanding, the pockets1170,1172can have a different geometry and arrangement on the foil section1122. For example, as shown inFIG. 11, the first pocket1170can have a first shape and be arranged generally between the collection of the tubular conduits1146,1148,1149and the tubular conduit1152. The second pocket1172can have a second shape and be arranged generally between the fourth tubular conduit1152and the trailing edge1134. With the differing shape of the first and second pockets1170,1172the foil section1122can be adapted to exhibit buoyance and ballast properties that can be different from those exhibited, for example, by the foil section922. In other cases, other geometries are possible and contemplated herein.

Modular foil depressors applied to umbilicals or other similar type cables can also be scaled by how many are deployed, for example, by daisy-chaining depressor sections at intervals along the cable. As described herein, modular foil depressors, including various combination of foil sections, shapes, systems, and so forth may be used to generate a negative lift (e.g., along a perpendicular direction) that depresses or maintains components of a marine array at a submerged depth.

To facilitate the reader's understanding of the various functionalities of the embodiments discussed herein, reference is now made to the flow diagram inFIG. 12, which illustrates process1200. While specific steps (and orders of steps) of the methods presented herein have been illustrated and will be discussed, other methods (including more, fewer, or different steps than those illustrated) consistent with the teachings presented herein are also envisioned and encompassed with the present disclosure.

In this regard, with reference toFIG. 12, process1200relates generally to positioning a modular foil system in a marine array. The process1200may be used with any of the foil systems, modular foil systems, and so forth, described herein, such as the foil systems500,600and modular foil system700, and variations and embodiments thereof.

At operation1204, a towed marine, system, array or device is launched. In some cases, the array may include a cable configured to carry a payload and a modular foil system coupled to the cable.

As one example and with reference toFIG. 2the seismic array200may be launched into a marine environment. The seismic array200may include various cables, such as the cross cable208. The seismic array200may also include a modular foil system coupled to the cable, such as the modular foil depressor220.

At operation1208, positional data is acquired for the towed cable, payload, or other towed device. For example and with reference toFIG. 1, one or more sensors of the seismic array100may determine or detect a position of an instrument payload towed by a vessel.

At operation1212, the acquired positional data is compared with an operational target, such as a target position, for the towed cable, payload, or other towed device. For example and with reference toFIG. 1, the seismic array may include one or more processing units, including computer executable instructions, that operate to compare the acquired positional data with a target position. In turn, at operation1216, the processing unit or other associated equipment, may determine the positional data is within operational tolerances. For example, the processing unit and/or other associated component may determine an adjustment parameter for the modular foil system based on the comparing of the acquired positional data and the target position. This adjustment parameter may in turn be used to adjust an angle of attack and control lift of the modular foil system.

For example, at operation1220, an angle of attack may be adjusted for one or more modular foil systems of the array. This may involve adjusting an angle of attack of a foil section relative to other components of the array. For example and with reference toFIG. 7, a group of foil sections of a first module700amay be adjusted relative to an angle of attack of a second group of foil sections700b. To facilitate the foregoing, a tension in through cables supporting the first group of foil sections may be adjusted independent of a tension in a second pair of through cables that supports the second group of foil sections. Accordingly, the first group of foil sections may generate a lift that is distinct from a lift generated by the second group of foil sections. This may be facilitated by an actuator, such as a dynamic actuator, that uses the adjustment parameter to control the tension and adjust the angle of attack.

The method ofFIG. 12may, subsequent to the operation1220, return to the operation1208. At the second iteration of the operation1208, the method1200may proceed by acquiring positional data for the towed payload subsequent to the adjustments to the angle of attack of the operation1220. In this regard, the method1200may continue and determine whether the adjustments to the angle of attack achieved the appropriate or desired position of the towed payload. For example, at the second iteration of the operation1212the acquired positional data (for the payload influenced by the adjusted angle of attack of operation1220) is compared with a target position for the towed cable, payload, or other towed device. In turn, at the second iteration of the operation1216, the subsequently acquired positional data is determined to be within operation tolerance.

In this regard, upon a determination at the operation1216that the acquired positional data is within operation tolerance, the method1200may proceed to operation1224. At the operation1224, towing may be continued (or commenced) for the marine system, array, or device.

FIG. 13depicts another embodiment of a marine array. In particular,FIG. 13shows a marine array1300. The marine array1300, as within any of the marine arrays described herein, may be, or be associated with, a seismic array, a fishing trawl, a military application, an oceanographic study, and/or substantially any other maritime application. The embodiment ofFIG. 13shows the marine array having towed cable and payload that is steered or positioned within a marine environment by a starboard and a port biased foil system.

To facilitate the foregoing, the marine array includes a vessel1302. The vessel1302is shown positioned along a surface of an marine environment1304. Attached to the vessel1302is a tow cable1306. The tow cable1306may be towed through the marine environment1304by the vessel1302. The tow cable1306may carry or pull a towed body or other payload1308through the marine environment1304. In some cases, a streamer cable1314may be pulled by the towed body1308through the marine environment1304.

It may be desirable to steer, position, stabilize, and so on the towed body1308and associated components within the marine environment1304. In this regard,FIG. 13shows the marine array1300including a first foil system1310and a second foil system1312coupled with the towed cable1306. The first foil system1310and the second foil system1312may be substantially analogous to any of the foil systems described herein. As such, the first foil system1310and the second foil system1312may each include a group of foil sections collectively defining an angle of attack and thus be configured to generate lift.

In one embodiment, the first foil system1310may have an angle of attack that causes the first foil system1310to generate lift that biases the towed cable1306toward a starboard direction. Further, the second foil system1312may have an angle of attack that causes the second foil system1321to generate lift that biases the towed cable1306toward a port direction. In this regard, the first foil system1310and the second foil system1312may counteract one another and thus help stabilize or otherwise control a position of the towed body1308in the marine environment1304. In some cases, the angle of attack of one or both of the first foil system1310or the second foil system1312may have an adjustable angle attack, which may be manipulated to help steer the towed body1308, as may be appropriate for a given application.

Other examples and implementations are within the scope and spirit of the disclosure and appended claims. For example, features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, “or” as used in a list of items prefaced by “at least one of” indicates a disjunctive list such that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Further, the term “exemplary” does not mean that the described example is preferred or better than other examples.