Patent Application
20140314491
Embodiments of the subject matter disclosed herein generally relate to methods and systems associated with seismic surveying and, more particularly, to mechanisms and techniques for performing maintenance on seismic streamers.
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. While this profile does not necessarily provide an accurate location for the oil and gas, it suggests, to those trained in the field, the presence or absence of oil and/or gas. 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 in
The streamers 12 are shown in
An example of a front-end gear 30 is shown in
Considering the above described deployment examples, when deployed, the seismic streamer can be quite long in length, e.g., multiple kilometers, and heavy. Occasionally portions of the seismic streamer can fail in operation and need to be replaced. When a portion of the streamer, e.g., a streamer node/module or interface portion, fails it can be desirable to replace it as efficiently and safely as possible. One method for replacing a failed portion of the streamer is to fully recover the seismic streamer onboard the mother ship (streamer vessel). However, this is a slow procedure, e.g., 12-24 hours of downtime, which is inefficient and costly.
Another method for replacing a failed portion of the streamer is to send out a smaller boat, e.g., a work boat, from the mother ship. The work boat can position itself to retrieve a portion of the streamer in a location near the failed portion of the seismic streamer. As shown in
However, if the portion of the seismic streamer 38 to be worked on is close enough to the spacers 36 which connect the streamers, it can be difficult, unsafe and in some cases not possible to utilize the method shown in
Accordingly, it may be desirable to have systems and methods for improving the ability to perform maintenance on seismic streamers which have been deployed.
According to an exemplary embodiment, there is a maintenance method for raising and lowering a portion of a spread associated with a seismic streamer which is towed by a mother ship, the method including: configuring a device to be movable, wherein the device includes at least two buoyant structures connected by a platform, further wherein the platform includes a winch, a motor and controls associated with the winch and the motor; deploying the device from the mother ship; positioning the device launched from the mother ship overtop of the portion of the spread to be raised; lowering a line from the device via a winch to a position proximate the portion of the spread to be raised; connecting the line to the portion of the spread; raising the line and the portion of the spread via the winch to a surface of a body of water; and returning the device to the mother ship.
According to another exemplary embodiment, there is a method for performing maintenance on a portion of a spread associated with a seismic streamer which is towed by a mother ship, the method including: deploying a device from a mother ship, wherein the device includes at least two buoyant structures connected by a platform, further wherein the platform includes a winch, a motor and controls associated with the winch and the motor; configuring the device to be deployable for temporary situations; configuring the device to support maintenance operations on the portion of the spread; configuring the device to be moved by a work boat; positioning the device overtop of the portion of the spread to be raised for maintenance work; operating the winch to lower a line from the device to a position proximate the portion of the spread to be raised; configuring the line to be connected to the portion of the spread; configuring the motor to interact with the winch to raise the line and the portion of the spread to a surface of a body of water; and performing maintenance on the portion of the spread.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:
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 single seismic streamer. However, the embodiments to be discussed next are not limited to these structures, but may be applied to other structures that are towed, e.g., a plurality of seismic streamers.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
According to exemplary embodiments, it can be desirable to have methods and systems which are more efficient than conventional methods for performing maintenance on deployed seismic streamers, e.g., a towed cable or towed array which can include one or more hydrophones and other environmental sensors for determining environmental conditions such as water salinity and water temperature. Prior to describing these systems and methods, an environment in which these systems and methods can be used will first be described.
As shown in
As described in the Background section, when maintenance work needs to be performed on the front head 50 or other gear associated with the front head 50, the seismic streamer 58 is typically retrieved, i.e., reeled back onto the mother ship 46, due to safety issues of working on the front head 50 from a work boat 51. According to exemplary embodiments, there are systems and methods which can be implemented for performing maintenance on the front head 50, or other portions of the seismic streamer 58, while the seismic streamer 58 is deployed, two initial configurations of which are described below and shown in
According to an exemplary embodiment, two floats 60 can be used in conjunction with a platform 62 to raise a portion of the seismic streamer 58 (or spread) to the surface 54 of the body of water as shown in
The two floats 60 are configured to be sufficiently buoyant enough and structurally sound to counter the high force level generated by lifting this portion of the seismic streamer 58, which required force is magnified by the relative closeness of the spacers between the various seismic streamers (see
The floats 60 can be Dilfloats, each of which is approximately three meters long with a 2000 liter volume, although embodiments are not limited to implementation with such Dilfloats. Once the portion of the seismic streamer 58 is on the surface 54 of the body of water, maintenance can then be performed using the workboat 51 as described in the Background section. Upon completion of the maintenance, the seismic streamer 58 can be lowered back to its original depth, and detached from the line 70. The platform 62 can then be returned to the mother ship 46 by the work boat 51. Additionally, while the connection point 72 is shown near the front head 50, the connection point 72 could be elsewhere on the seismic streamer 58 as desired.
According to another exemplary embodiment, another configuration can also be used as shown in
According to an exemplary embodiment, the float 74 will now be described in more detail. As shown in
The exemplary embodiments described above show raising a portion of the seismic streamer 58 near the front head 50. By using the systems and methods described herein, the down time of the seismic streamer 58 to replace a module in this section can be reduced from the current normal time, e.g., 12-24 hours, to as little as 20-30 minutes. This is a noticeable improvement in efficiency which can also allow for reduced operational costs. These embodiments also describe a device which may either be the float 74 or the platform 62 with multiple floats 64. This equipment may be stored on the mother ship 46 and deployed on an as needed basis.
Utilizing the above described exemplary systems according to exemplary embodiments, a maintenance method for raising and lowering a portion of a seismic streamer is shown in the flowchart of
Utilizing the above described exemplary systems according to exemplary embodiments, a method for performing maintenance on a portion of a seismic streamer is shown in the flowchart of
The disclosed exemplary embodiments provide a system and a method for towing an array of streamers underwater. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.
