Marine geophysical data recording, in particular seismic data recording, may be performed with “nodal” recorders used to acquire seismic or electromagnetic data regarding Earth formations below a body of water such as a lake or ocean. Nodal recorders or ocean-bottom nodes (OBN) are self-contained devices that are disposed at selected positions on the bottom of a body of water such as a lake or the ocean. An energy source deployed in the water is actuated at selected times and signals generated by sensors in the nodes are stored in a recording device associated with each node. Practical applications for node acquisition begin with accuracy of placement. Node placement is typically carried out with a planting frame or remotely operated vehicle (ROV).
Ocean-bottom nodes utilizing built-in navigation and trajectory control systems have also been developed to improve accuracy during placement operations. A node so equipped can be deployed from the surface and is capable of autonomously making lateral corrections to its position as it sinks to the bottom. Yet, such nodes may be more difficult to deploy in shallow water, for example, where the node does not have as much time to make large corrections laterally, given the depth of the water and the shorter time before the node reaches the bottom. Thus, a marine vessel deploying the nodes may need to move closer to the intended position of each node, making the process of deploying the nodes more time-consuming, especially if the nodes are to be deployed over a large area.
For a detailed description of example embodiments, reference will now be made to the accompanying drawings in which:
Various terms are used to refer to particular system components. Different companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to. . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections.
“Cable” shall mean a flexible, load carrying member that also comprises electrical conductors and/or optical conductors for carrying electrical power and/or signals between components.
“Rope” shall mean a flexible, axial load carrying member that does not include electrical and/or optical conductors for carrying electrical power and/or signals between components. Such a rope may be made from fiber, steel, other high strength material, chain, or combinations of such materials.
“Line” shall mean either a rope or a cable.
“Substantially” shall mean, with respect to distance measures, a change of five percent (5%) or less of the distance.
The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.
This disclosure is related generally to the field of marine surveying. Marine surveying can include, for example, seismic and/or electromagnetic (EM) surveying, among others. For example, this disclosure may have applications in marine surveying, in which one or more sources are used to generate wave-fields, and receivers—either towed or ocean bottom—receive energy generated by the sources and affected by interaction with subsurface formations. The receivers can take the form of ocean-bottom nodes (OBN). The present disclosure is related to deployment of ocean-bottom nodes using deflectors. More particularly, various example embodiments are directed to a vessel towing a deflector with a pulley system implemented between the vessel and the deflector. The pulley system is used to suspend a plurality of ocean-bottom nodes between the vessel and the deflector. When the ocean-bottom nodes are in the correct position (e.g., above a desired location on the sea floor) the ocean-bottom nodes are released from the pulley system and are thus allowed to sink to the sea floor. Having multiple ocean-bottom nodes along a pulley system enables simultaneous or near-simultaneous release, and also enables for more efficient placement in shallow water. The specification first turns to a description of an example system for ocean-bottom node deployment.
As shown in
A deflector 36 is connected to the pulley system 24 and configured to position the pulley system 24 relative to the marine vessel 30. In more detail, the deflector 36 is disposed remotely from the marine vessel 30 on a first side 38 of the marine vessel 30 and a second deflector 36′ may be disposed remotely from the marine vessel 30 on a second side 40 of the marine vessel 30 opposite the first side 38. The system 20 can also include a second pulley system 24′ including a second transport line 32′ extending between the second deflector 36′ and the marine vessel 30. The pulleys 26, 26′ are connected to respective deflectors 36, 36′. So as not to unduly complicate the description of the system 20, the system 20 will primarily be described below with reference only to deflector 36; nevertheless, it should be appreciated that the marine vessel 30 can deploy one or more deflectors 36, 36′ and pulley systems 24, 24′.
With reference to
The central control unit 44 further includes a central positioning system 50 (e.g., a navigation system of the marine vessel 30) configured to determine a vessel position and a vessel speed of the marine vessel 30. So, the central processor 46 is further configured to determine a vessel position and a vessel speed of the marine vessel 30 using the central positioning system 50. In addition, the central processor 46 of the central control unit 44 can be further configured to control the traction wheel 28 to move the transport line 32 at a line speed based on the vessel speed of the marine vessel 30. However, it should be appreciated that in some embodiments, the transport line 32 could be moved by another mechanism besides or in addition to the traction wheel 28.
In the embodiment shown in
A release processor 60 is electrically coupled to the release mechanism 54 and is electrically coupled to and powered by the release power supply 52. Each release unit 34 also may include a release positioning system 62 coupled to the release processor 60 and configured to determine the unit position. Thus, the release processor 60 is further configured to monitor the unit position using the release positioning system 62. The release unit 34 can, for example, have global positioning system (GPS) capability to operate out of the water and an acoustic positioning unit to operate during times when the release unit 34 is submerged (e.g., as the release unit 34 approaches the deflector 36 remotely from the marine vessel 30). Furthermore, the release unit 34 could additionally include inertial guidance (e.g., a gyroscope, accelerometers) for determining the unit position during times that the release unit 34 is submerged, for instance.
Still referring to
In operation, the release processor 60 is configured to receive a drop signal from the central control unit 44 using the release communication unit 64 and to release the one of the plurality of ocean-bottom nodes 22 using the release mechanism 54 in response to receiving the drop signal. Therefore, the release unit 34 can be controlled based on communication with the central control unit 44. For example, the release processor 60 can communicate the unit position to the central communication unit 48 using the release communication unit 64. When an ocean-bottom node 22 is in a predefined position along the pulley system 24, for instance, as determined by the central control unit 44 (e.g., based on the release communication unit 64 communicating the unit position to the central communication unit 48 of the central control unit 44), the release unit 34 can release the ocean-bottom node 22. In other embodiments, the central control unit 44 may determine when to send the drop signal using an inferred position of the release unit 34 on the transport line 32. Specifically, if the line speed, position of each particular release unit 34 on the transport line 32, and deflector position of the deflector 36 are known to the central control unit 44, the central control unit 44 could estimate when a particular release unit 34 reaches the predefined location and send the drop signal at that time (e.g., without receiving the unit position from the release unit 34). Alternatively or in addition, an indicator could be affixed to the transport line 32 and the position of such an indicator can be sensed by the central control unit 44 when it reaches a certain point on or near the marine vessel 30. Thus, because the positions of each release unit 34 are fixed on the transport line 32, the position of each ocean-bottom node 22 along the transport line 32 may be inferred by the central control unit 44 based on the position of the indicator and transport line 32 relative to the marine vessel 30.
While the drop signal sent from the central communication unit 48 of the central control unit 44 to the release communication unit 64 may lead to the release unit 34 dropping or releasing the ocean-bottom node 22 immediately after the release communication unit 64 receives the drop signal, it should be appreciated that, in other embodiments, the drop signal may not result in such an immediate release. In more detail, the drop signal could comprise a drop location (e.g., the predefined position at which the ocean-bottom node 22 should be released) and after the release communication unit 64 receives the drop signal, the release processor 60 may store the drop location and release the one of the plurality of ocean-bottom nodes 22 using the release mechanism 54 once the release positioning system 62 identifies that the release unit 34 has reached the drop location, or is within a predetermined drop radius of the drop location. The specification now turns to a detailed description of an example deflector 36 that may be used with at least some embodiments, to enable the central control unit 44 to control positioning of the pulley system 24.
The deflector 36 further comprises an upper frame 74, to which the straps 72A-E are coupled. The illustrative deflector 36 also comprises a middle frame 76 and lower frame 78. Each of the frames 74, 76, 78 defines a long dimension, with the long dimension indicated as Lo in the figure. Coupled between upper frame 74 and the middle frame 76 are a plurality of upper diverter plates 80A-D. The illustrative deflector 36 further comprises a plurality of lower diverter plates 82A-D coupled between middle frame 76 and the lower frame 78. In some cases, the upper diverter plates 80A-D are separate mechanical elements from lower diverter plates 82A-D, and in other cases each diverter plate is a single element that extends through middle frame 76 (e.g., upper diverter plate 80A and lower diverter plate 82A may be a single unit extending through the middle frame 76). Greater or fewer diverter plates 80A-D, 82A-D may be equivalently used. The diverter plates 80A-D, 82A-D are designed in such a way as to re-direct water flow through the plates 80A-D, 82A-D such that a lateral force is developed. The diversion of water by the diverter plates 80A-D, 82A-D to create the force may be based on an angle a of the diverter plates 80A-D, 82A-D relative to the direction of water flow along the axis A. While the diverter plates 80A-D, 82A-D are shown as having a curvature or an airfoil-type cross-section, some or all the plates 80A-D, 82A-D may instead be flat, or the deflector 36 may include some combination of flat and curved diverter plates 80A-D, 82A-D.
It is noted that deflector 36, having three frames 74, 76, 78 and two sets of diverter plates 80A-D, 82A-D extending between the frames 74, 76, 78, is merely illustrative. The various embodiments may be equivalently implemented on deflectors 36 having only a single set of diverter plates 80A-D, 82A-D extending between two frames 74, 76 (e.g., just upper diverter plates 80A-D), as well as deflectors 36 having three or more sets of diverter plates (e.g., diverter plates 80A-D, 82A-D, and other sets below lower diverter plates 82A-D).
Before proceeding, it is noted that deflector 36 moves through the water at an angle a relative to the direction of travel. Consider the axis A of the float 66. The motion of the deflector 36 through the water indicated by arrow m forms an acute angle a with the axis A (e.g., along the long dimension LD of any frame). The precise angle a depends on a variety of factors, such as speed of the deflector 36 relative to the water, bridle geometry, and the amount of resistance to movement the deflector 36 presents. The force created is substantially perpendicular to the illustrative axis A, and also substantially normal to a plane defined by the diverter plates 80A-D, 82A-D, with the approximate direction indicated by arrow F. While the direction of movement of the deflector 36 may be at an acute angle a with respect to the illustrative axis A, the leading vertical geometry (e.g., diverter plates 80A, 82A) shall be considered “forward” for purposes of this specification and claims.
Continuing to refer to
In accordance with the illustrated embodiment, the amount of force developed by the deflector 36 is controllable during use (e.g., as the deflector 36 is towed through the water) by selective control of the location of the tow points 86, 96, 98, 100, 102, 104, 106 relative to the frames 74, 76, 78. For example: the location of the upper forward tow point 96 and the corresponding upper aft tow point 98 relative to the upper frame 74 may be changed (while the distance between the tow points 86, 100, 102, 104, 106 remains unchanged); the location of the location of the middle forward tow point 100 and the corresponding middle aft tow point 102 relative to the middle frame 76 may be changed (while the distance between the tow points 86, 96, 98, 104, 106 remains substantially unchanged); and/or the distance between the lower forward tow point 104 and the corresponding lower aft tow point 106 relative to the lower frame 78 may be changed (while the distance between the tow points 86, 96, 98, 100, 102 remains substantially unchanged). Changes in the location of the upper forward tow point 96, upper aft tow point 98 middle forward tow point 100, middle aft tow point 102, lower forward tow point 104, and lower aft tow point 106 relative to the frames 74, 76, and 78 may result in changes of an angle of attack of the diverter plates 80A-D, 82A-D. Consequently, a magnitude of the lateral force developed by the diverter plates 80A-D, 82A-D changes accordingly. For example, during turns the diverter plate with a short radius (e.g., 80A and 82A) may be adjusted to have its angle of attack increased to compensate for reduced relative velocity between the diverter plate 80A, 82A and the water (e.g., by moving the tow points aft), and the diverter plate with a larger radius (e.g., 80D and 82D) may have its angle of attack decreased to compensate for increased relative velocity between the diverter plate 80D, 82D and the water (e.g., by moving the tow points forward). Similarly, in operational situations where a cross-current exists relative to the intended direction of travel of the marine vessel 30, the angle of attack as between the diverter plates 80A-D, 82A-D may be adjusted to compensate. Now that the external structure of the example deflector 36 has been described, the specification now turns to an example control system for the deflector 36.
In order to know when to operate the linear actuator(s) 110, the deflector control system 108 may couple to a deflector communication unit (com system) 120. The deflector communication unit 120 may take any suitable form, such as a radio-based system communicating by way of antenna 70, or a system configured to communicate over electrical or optical conductors, such as when the tow line 42 coupled to the deflector 36 is a cable as defined herein. Regardless of the precise system implemented by the deflector communication unit 120, the deflector control system 108 may receive signals indicative of instructions to change the distance between respective sets of forward and aft tow points 96, 98, 100, 102, 104, 106 (i.e., respective sets being associated with a particular frame), and/or receive instructions to change the location of the tow points 96, 98, 100, 102, 104, 106). The deflector 36 may also utilize the deflector communication unit 120 to communicate the deflector position of the deflector 36 to the central control unit 44. So, for example, the traction wheel 28 may be controlled by the central processor 46 using input from the acoustic positioning unit 118 (or other deflector positioning system).
In the illustrative case of one or more of the linear actuator(s) 110 on the deflector 36 being a hydraulic cylinder 124, the system may comprise a hydraulic pumping unit 126 disposed at least partially within the float 66. In some cases, the hydraulic pumping unit 126 may draw operational power from the battery system 112, may draw operational power directly from the water flowing past the deflector 36, or some combination thereof. Regardless, the hydraulic pumping unit 126 may provide hydraulic fluid under high pressure to cause the axial length of the illustrative hydraulic cylinder 124 to change responsive to signals from the marine vessel 30 or some other location.
Still referring to
As discussed above, the linear actuator(s) 110 need not be hydraulic cylinders 124. Other devices with controllable lengths may be equivalently used. For example,
Returning to
While the deflector 36 above is discussed as including adjustment of the geometry of the bridle assembly 84 relative to the diverter plates 80A-D, 82A-D, it should be understood that deflectors 36, 36′ with fixed vanes or diverter plates 80A-D, 82A-D and without adjustment of the geometry of the bridle assembly 84 can be utilized instead. Thus, instead of adjusting the diverter plates 80A-D, 82A-D using the deflector control system 108 to move the pulley system 24, 24′ and plurality of release units 34 into the desired position, in such an embodiment, the vessel speed of the marine vessel 30 may be varied to move the pulley system 24, 24′ into a desired position.
The method can proceed with the step of 206 deploying a plurality of ocean-bottom nodes 22 from the marine vessel 30 via a plurality of release units 34 coupled to a transport line 32 of the pulley system 24 (
Still referring to
More specifically, 214 determining a unit position of each of the plurality of release units 34 and the deflector position of the deflector 36 can include the steps of 218 monitoring a unit position of each of the plurality of ocean-bottom nodes 22 using a release positioning system 62 of each of the plurality of release units 34 and 220 communicating the unit position using a release communication unit 64 of each of the plurality of release units 34. The method can continue by 222 receiving the unit position with a central communication unit 48 of the central control unit 44 and 224 sending a drop signal from a central control unit 44. Then, the next steps of the method are 226 receiving a drop signal from a central control unit 44 in communication with a release communication unit 64 of one of the plurality of release units 34 and 228 releasing the one of the plurality of ocean-bottom nodes 22 at the predefined position with one of the plurality of release units 34 in response to receiving the drop signal. The method may also include the step of 230 controlling a line speed of the transport line 32 between a traction wheel 28 and a pulley 26 of the pulley system 24 using input from a central positioning system 50 of the central control unit 44.
Advantages of the the inventive systems and methods can include providing the ability to deploy multiple ocean-bottom nodes 22 on transport lines 32 simultaneously from one marine vessel 30 to quickly and efficiently deploy the plurality of ocean-bottom nodes 22 over a large area (
It is to be understood the present disclosure is not limited to particular devices or methods, which may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used herein, the singular forms “a”, “an”, and “the” include singular and plural referents unless the content clearly dictates otherwise. Furthermore, the words “can” and “may” are used throughout this application in a permissive sense (i.e., having the potential to, being able to), not in a mandatory sense (i.e., must). The term “include,” and derivations thereof, mean “including, but not limited to.” The term “coupled” means directly or indirectly connected.
Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the present disclosure, even where only a single embodiment is described with respect to a particular feature. Examples of features provided in the disclosure are intended to be illustrative rather than restrictive unless stated otherwise. The above description is intended to cover such alternatives, modifications, and equivalents as would be apparent to a person skilled in the art having the benefit of this disclosure.
The scope of the present disclosure includes any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Various advantages of the inventive systems and methods have been described herein, but embodiments may provide some, all, or none of such advantages, or may provide other advantages.
The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/632,543 filed Feb. 20, 2018 titled “Node Deployment Using Deflectors.” The provisional application is incorporated by reference herein as if reproduced in full below.
Number | Date | Country | |
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62632543 | Feb 2018 | US |