1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to techniques for providing a safety mechanism for a blowout preventer.
2. Discussion of the Background
A subsea blowout preventer (“BOP”) stack is used to seal a wellbore during drilling operations, both for safety and environmental reasons. As shown in
In typical configurations, the lower BOP stack 14 may be rigidly affixed atop a subsea wellhead and may include (among other devices) a ram-type blowout preventer (BOP) 28 useful in controlling the well as it is drilled and completed. Similarly, the LMRP 18 may be disposed upon a distal end of a long flexible riser 20 that provides a conduit through which drilling tools and fluids may be deployed to and retrieved from the subsea wellbore. Ordinarily, the LMRP 18 may include (among other things) a ram-type blowout preventer at its distal end such that, when desired, ram-type blowout preventers of the LMRP 18 and the lower BOP stack 14 may be closed and the LMRP 18 may be detached from the lower BOP stack 14 and retrieved to the surface, leaving the lower BOP stack 14 atop the wellhead.
During the operation of the lower BOP stack 14 and/or the LMRP 18, various incidents or simply maintenance events may occur that require access to the BOP 28. For this purpose, the well might be shut down and the part necessary to be worked on may be lifted to the vessel 22. If the equipment necessary for repairing the BOP 28 is not available on the vessel 22, the BOP 28 is shipped to dry locations where the equipment is available. As the BOP 28 is connected to other parts of the lower BOP stack 14 and/or the LMRP 18, which parts may be heavy and linked to the BOP in a complicated manner, it is the practice to remove the whole lower BOP stack 14 and/or LMRP 18 and bring it to the surface for repairs or inspection.
Thus, the weight of the entire lower BOP stack may be in the range of millions of kg and a height of the stack may be up to 10 m. Especially when the repair and/or inspection of the lower BOP stack 14 and/or LMRP 18 is performed on the vessel 22, the sea waves may sometimes tilt these devices so violently that maintenance personnel working around the lower BOP stack 14 and/or LMRP 18 may get injured or even lose their lives.
Accordingly, it would be desirable to provide systems that avoid the afore-described problems and drawbacks.
According to one exemplary embodiment, there is a blowout preventer (BOP) stack and lower marine riser package for sealing an undersea well. The blowout preventer stack includes a frame extending along an axis and configured to be attached to a head of the well; an accumulator attached to the frame and configured to provide high pressure; two or more BOPs attached to the frame, the two or more BOPs being disposed within the frame and attached one on top of the other along the axis; each BOP having a body and a pair of bonnets attached to the body, wherein the bonnets are configured to be detachably attached to the body; each BOP having a corresponding cavity extending along the axis through which a fluid from the well is circulating; each BOP being configured to seal the well when the high pressure from the accumulator is released to the BOPs; plural brackets attached to the body of at least one BOP; and a safety bar attached to the plural brackets and configured to partially encircle the body of the at least one BOP.
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 BOP stacks. However, the embodiments to be discussed next are not limited to these systems, but may be applied to other systems that require the presence of a person at a high height or in an unstable environment, as for example, the LMRP.
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.
As discussed above with regard to
A more detailed view of the lower BOP stack 14 is shown in
According to an exemplary embodiment, at least one BOP 28 of the plural BOPs may be provided with a safety bar 50 that is firmly (permanently) attached to a body of the BOP. Having the safety bar 50 provided around the BOP, the maintenance personnel may attach a safety clip (not shown) to the safety bar 50, thus, securing a harness that is worn by the maintenance personnel to the safety bar 50. For example, the safety bar 50 may be welded, screwed or otherwise attached to the body of the BOP 28-2 as would be recognized by those skilled in the art. According to an exemplary embodiment, the safety bar 50 is provided to completely encircle the body of the BOP 28-2, as shown in
A detailed view of a bracket 56, according to an exemplary embodiment, is shown in
According to an exemplary embodiment shown in
In addition, the distribution of the safety bar 50 at the top part of the BOP and around the body 52 of the BOP offers the maintenance personnel the freedom to move around the BOP for various maintenance operations. According to another exemplary embodiment, the safety bars 50 may be used to restrain the movement of the maintenance personnel at the periphery of the lower BOP stack 14 while allowing them to work inside the frame 40.
Carbon steel 4130 may be used to produce the safety bars 50. Carbon steel 75 ksi (ksi=1000 psi) tensile strength may be used for 1-, 1.25- and 2.0-inch diameter safety bars, 95 ksi may be used for 1.50 in and 60 ksi may be used for 1.75 in. These dimensions of the safety bar ensures that the bars are configured to withstand a minimum of 5000 lbs per rig personnel.
According to an exemplary embodiment, the safety bar 50 may have a flat band profile having a t-slot 60 machined at a side 62 as shown in
According to another exemplary embodiment as shown in
According to another exemplary embodiment shown in
The disclosed exemplary embodiments provide a system for increasing the safety of operating personnel when working on a BOP. 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 example are intended to be within the scope of the claims.