Anti-attachment device and method

Method and an anti-attachment device configured to be provided on a streamer. The anti-attachment device includes a body configured to be provided around the streamer and a first end is configured to be rotatably attached to the streamer.

BACKGROUND

1. Technical Field

Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for preventing various marine animals from attaching to seismic equipment.

2. Discussion of the Background

During the past years, the interest in developing new oil and gas production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of fossil fuel. Offshore drilling is an expensive process. Thus, those engaged in such a costly undertaking invest substantially in geophysical surveys in order to more accurately decide where to drill in order to avoid a dry well.

Marine seismic data acquisition and processing generate a profile (image) of the geophysical structure (subsurface) under the seafloor. This profile is used by those trained in the field, to evaluate the presence or absence of oil and/or gas traps. Thus, providing a high resolution image of the subsurface is an ongoing process for the exploration of natural resources, including, among others, oil and/or gas.

During a seismic gathering process, as shown inFIG. 1, a vessel10drags an array of seismic detectors provided on streamers12. The streamers may be disposed horizontally, i.e., lying at a constant depth relative to a surface14of the ocean. The vessel10also drags a sound source assembly16that is configured to generate an acoustic wave18. The acoustic wave18propagates downwards toward the seafloor20and penetrates the seafloor until eventually a reflecting structure22(reflector) reflects the acoustic wave. The reflected acoustic wave24propagates upwardly until is detected by a detector on streamer12.

The above noted arrangement is towed under water for days if not weeks for a given survey. Thus, it was noted that various marine animals, e.g., barnacles, attach to various components of the streamer, e.g., electronic components. The barnacles may change a desired weight of the streamer, may make the streamer deviate from its desired towed position or simply may make it difficult to manipulate the streamer for maintenance or when deployed under water.

Traditional methods employ a cleaning device that is configured to move along the streamer and clean the streamer from the marine animals. However, there are problems with these devices as they are bulky and they need to travel along various elements (e.g., birds, electronic boxes, etc.) connected to the streamer. Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks.

SUMMARY

According to one exemplary embodiment, there is a streamer having plural sections connected to each other. The streamer includes an anti-attachment device provided around one of the plural sections and configured to rotate relative to the one of the plural sections but not to move along the one of the plural sections.

According to another exemplary embodiment, there is an anti-attachment device configured to be provided on a streamer. The anti-attachment device includes a body configured to be provided around the streamer; and a first end configured to be rotatably attached to the streamer.

According to still another exemplary embodiment, there is a method for agitating water around a streamer. The method includes a step of providing an anti-attachment device along the streamer; and a step of rotationally fixing the anti-attachment device on the streamer so that the anti-attachment device rotates but does not moves along the streamer when towed underwater.

DETAILED DESCRIPTION

The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of a streamer having an electronic module. However, the embodiments to be discussed next are not limited to these structures, but may be applied to other structures that are exposed to a marine environment.

According to an exemplary embodiment, there is a section of a streamer that is covered by a anti-attachment device that is configured to rotate in order to prevent the barnacles or other marine animals to attach to the streamer. In one configuration, the anti-attachment device is configured to rotate around the streamer but not travel along the streamer. The anti-attachment device can cover a limited portion of the streamer or an entire section of the streamer. The anti-attachment device may only form turbulences in the water, next to the streamer, in order to prevent the marine animals to attach to the streamer. However, the anti-attachment device may be provided with various devices for scrubbing the streamer, or distributing a chemical around the streamer, or other purposes.

According to an exemplary embodiment shown inFIG. 2, an anti-attachment device30is shown provided over a streamer40. The anti-attachment device is configured to rotate along an axis A but not to move along axis X. Assuming that the streamer is towed along the axis X, a first end32of the anti-attachment device30is rotatably fixed to the streamer40so that the anti-attachment device30is prevented from moving along axis X. In another exemplary embodiment, both ends32and34may be rotatably fixed to the streamer40. The streamer40may include plural sections40A-C. Various devices (e.g., a bird) may be provided between the streamers.

According to an exemplary embodiment illustrated inFIG. 3, the end32of the anti-attachment device30may be rotatably fixed to the streamer40by a ring42. The ring42is fixedly attached to the streamer40but is provided with a groove44in which a flange36of the anti-attachment device30is configure to fit. In this way, the flange36is allowed to rotate relative to the streamer40but not allowed to move along axis X. The other end34of the anti-attachment device30may be free, may have the same structure or the structure shown inFIG. 3. According toFIG. 3, another ring46may be fixedly attached to the streamer40to rotatably support end34but prevent is X movement. According to another embodiment, the anti-attachment device30may have another flange38configured to slide over a side of the ring46. One skilled in the art would understand that these elements may be modified to still achieve the same effects, i.e., rotation and no translation. Regarding the term translation, it is understood that in fact the anti-attachment device30can slightly translate along the X axis but not freely, e.g., between rings42and46. Other stopper structures may also be imagined.

In an exemplary embodiment illustrated inFIG. 4, the anti-attachment device is a spiral50that is provided around the streamer40so that parts40aof the streamer40are not covered by the spiral while parts40bof the spiral are covered. By providing vanes or deflectors or wings52on one or more portions of the spiral50, the spiral50rotates when towed under water, which will determine the portions40aand40bto continuously change so that all or most parts of the streamer are alternately covered and uncovered by the spiral. Thus, the effect of producing a water flow or water disturbances around the streamer is achieved.

The anti-attachment device30may have other shapes that achieve the above noted effect. For example, as shown inFIG. 5, an anti-attachment device60may have a cylindrical shape with various holes62formed in it. One or more wings64may be attached. The wings may be inflatable. The holes62may have a pattern or not, may be more or less, may be big or more, etc. Another shape is shown inFIG. 6in which an anti-attachment device70has no holes but only wings71. The number of wings may vary as a function of the length of the anti-attachment device, towing speed, etc. Other rotating shapes may be imagined.

The anti-attachment device may be formed from a plastic material that is light and resistant. Alternatively, the anti-attachment device may be formed from a metal that does not corrode easily, from a composite material, etc. Alternatively, the anti-attachment device may be provided with a coating layer74(e.g., an anti-fouling coating) to prevent marine animals to attach to the anti-attachment device. In another application, instead of coating the device with the anti-fouling material, a part or all of the anti-attachment device may be formed of a material having anti-fouling properties, e.g., copper. The anti-attachment device may be rigid or allow for a limited deformation as long as the deformation does not impede the rotation of the anti-attachment device. A clearance72between an interior diameter of the anti-attachment device and an exterior diameter of the streamer40may be in the order of millimeters to centimeters or tens of centimeters.

The anti-attachment device may be provided with various tools. For example, as shown inFIG. 7, the anti-attachment device30may be provided with a tool80, attached to the inside of the anti-attachment device and configured to touch the streamer40. The tool80may scrape the exterior of the streamer40or may dispense a chemical on the surface of the streamer40. The tool80is shown to be provided around the streamer40. However, a tool90, similar or different from tool80, may be provided to not enclose the streamer40.

In one exemplary embodiment, the anti-attachment device is provided with an anti-fouling coating to prevent the marine animals to attach to the anti-attachment device. In one application, an anti-sticking coating is provided inside the anti-attachment device to improve the rotation of the anti-attachment device relative to the streamer. In still another application, both ends of the anti-attachment device are rotatably fixed to the streamer. In yet another application, a brush is provided on the inside of the anti-attachment device. In another application the wings or vanes of the anti-attachment device are foldable for easy stowing and deploying while in another application the wings are inflated by the water when towed.

According to another exemplary embodiment illustrated inFIG. 8, a streamer100is provided with an actuating device102configured to rotate relative to the streamer. The actuating device102may include a ring that has a fixed part102A attached to the streamer and a rotatable part1028configured to rotate relative to the fixed part102A. The actuating device102may include wings104attached to the rotatable part1028so that when the streamer is towed underwater, the wings104determine the rotatable part102B to rotate. The anti-attachment device106may also be attached to the rotatable part1028so that the anti-attachment device is actuated by the actuating device102.

In another embodiment illustrated inFIG. 9, the anti-attachment device106is coupled to a motor120that is configured to rotate. The motor120may include a controller122that is configured to rotate the motor120with a desired speed and at desired time intervals. The speed and time intervals may be transmitted from the vessel to the controller along the streamer, or wirelessly from a global control device (not shown). The motor120is coupled to a battery124for receiving its electrical energy. The battery maybe recharged by the actuating device102discussed with regard toFIG. 8.

According to an exemplary embodiment illustrated inFIG. 10, there is a method for agitating water around a streamer. The method includes a step1000of providing an anti-attachment device along the streamer; and a step1002of rotationally fixing the anti-attachment device on the streamer so that the anti-attachment device rotates but does not moves along the streamer when towed underwater.

In addition, there is a method for providing a spiral type anti-attachment device around a streamer when deployed underwater for seismic exploration. The method includes a step of storing the streamer on a spool on a vessel; a step of deploying the streamer from the spool into the water while the vessel is moving; and a step of adding the spiral type anti-attachment device on the streamer as the streamer is unspooled from the spool. The spiral type anti-attachment device is added to the streamer after being unspooled but before being released into the water.