The present invention relates generally to subsea production systems, and more particularly to subsea production systems having a bypass flow path from a point below a tubing hanger to a point above a tubing hanger.
Some subsea production systems have a wellhead located at the upper end of a well. The wellhead typically suspends one or more casing strings. Connected to the top of the wellhead is a tubing spool. A tubing hanger typically lands in the tubing spool, and the tubing hanger suspends a tubing string through the wellhead into the casing string. A conventional production tree can be connected to the top of the tubing spool. Conventional production trees include vertical and horizontal trees. Horizontal trees can be incorporated as part of the spool system. Vertical trees typically have a vertical passageway that receives an upward flow of product from the tubing hanger and a vertical passageway that receives an upward flow of annular fluid. Horizontal trees typically include a passageway that receives a vertical flow of product and one or more lateral passageways for delivering product and possibly annular fluid.
Production trees may include single or dual bore systems. A dual bore system permits the use of a production bore and a tubing annulus bore. Horizontal production trees typically have a production bore and a large diameter tubing hanger. Large diameter bores are difficult to seal in the presence of a high pressure, which results in large upthrust forces. To alleviate some of the problems associated with large diameter wells, wells have been drilled in two stages using a two stack system. For example, wells may be drilled with stacks having sizes of 18.75 inches and 13.625 inches. Vertical trees may also be used, but they typically include a top terminated annulus. Vertical production trees may be used to reduce the diameter of the tubing hanger. However, a reduction in the diameter of the tubing hanger reduces the diameter of tools that may enter the production system without removing the tree. Conventional production trees generally are not well suited for high pressure production systems having small spool and/or wellhead diameters.
During production it may be desirable to remove a production tree and replace it with a blow out preventer (“BOP”) and safely perform work over tasks. Alternatively, a BOP stack located on top of a tree may be used to work over a well. A BOP stack, however, typically exerts a large bending load to points at and below the point of connection of the BOP stack with the production system. Removing a conventional tree can be a time and labor consuming task that involves some risk of well destruction.
The present invention is generally directed to a subsea production system, which includes a wellhead, a casing string suspended from the wellhead a tubing spool having a central bore connected to the wellhead, a tubing hanger disposed within the tubing spool and sealed thereto, a tubing string suspended from the tubing hanger through the wellhead into the casing string, an annulus disposed between the tubing string and the casing string, and a bypass annulus fluid flow path in fluid communication with the annulus. The subsea production system further includes a production tree connected to the tubing spool, which includes a production flow path that has a production master valve, a production wing valve and a production swab valve for controlling flow through the production flow path.
In one embodiment of the present invention, the bypass annulus fluid flow path passes through a separate annulus block. In this embodiment, the bypass annulus fluid flow path has a first end which is in fluid communication with the annulus and a second end which is in fluid communication with the central bore of the tubing spool above the tubing hanger. The bypass annulus fluid flow path further includes an annulus master valve and an annulus wing valve connected in series with the annulus master valve, which control flow into an annular flow line, which in turn connects with a subsea fluid flow system. The bypass annulus fluid flow path further includes a cross over valve connected in parallel with the annulus wing valve and which connects to an annular flow line that communicates with the production flow path in the production tree connected to the tubing spool. In an alternate form of this embodiment, the cross over valve controls flow to the BOP stack jumper, which in turn communicates with a central bore of a BOP. The bypass annulus fluid flow path may further include a work over valve connected in parallel with the annulus wing valve that controls flow into a central bore of the tubing spool.
In another embodiment of the present invention, the bypass annulus fluid flow path is integrated into the spool. In this embodiment, the bypass annulus fluid flow path includes a first end which is in fluid communication with the annulus and a second end which is in fluid communication with the central bore of the tubing spool above the tubing hanger. The bypass annulus fluid flow path further includes an annulus master valve and an annulus wing valve connected in series with the annulus master valve, which control flow into an annular flow line. The bypass annulus fluid flow path further includes a cross over valve connected in parallel with the annulus wing valve and which connects to an annular flow line that communicates with a central bore of the production tree. The bypass annulus fluid flow path further includes a work over valve connected in parallel with the annulus wing valve that communicates with a central bore of the tubing spool. In another form of this embodiment, the cross over valve connects the central bore of the tubing spool to a central bore of the production tree.
In another embodiment, the bypass annulus fluid flow path includes a first end which is in fluid communication with the annulus, a second end which is in fluid communication with the production flow path of the production tree, an annulus master valve and an annulus wing valve connected in series with the annulus master valve, which control flow into an annular flow line. In this embodiment, the subsea system further includes an annulus stab connected in parallel with the annulus wing valve and a cross over valve connected in series with the annulus stab, which controls flow into the production flow path.
In yet another embodiment, the bypass annulus fluid flow path passes through an annulus tree. In this embodiment, the bypass annulus fluid flow path includes a first end which is in fluid communication with the annulus and a second end which is in fluid communication with the central bore of the tubing spool above the tubing hanger. In this embodiment, the bypass annulus fluid flow path also includes an annulus master valve and an annulus wing valve connected in series with the annulus master valve, which control flow into an annular flow line. The bypass annulus fluid flow path further includes a work over valve connected in parallel with the annulus wing valve which controls flow into the central bore of the tubing spool. The subsea system according to present invention further includes a fluid line that connects the bypass annulus fluid flow path to the production flow path of the production tree and a cross over valve connected in parallel with the work over valve and disposed within said fluid line. In this embodiment, the cross over valve is disposed in the annulus tree. In another embodiment, the cross over valve is disposed in the production tree. In another embodiment, the subsea production system further includes a flow path connecting the central bore of the tubing spool to the production flow path in the production tree and a cross over valve disposed in the flow path connecting the central bore of the tubing spool and the production flow path in the production tree. In yet another embodiment of the present invention, the subsea production system further includes a work over valve connected in series with the annulus master valve that controls flow into the central bore of the tubing spool and a cross over valve connected in parallel with the annulus master valve, which connects flow to production flow path of the production tree. In still another embodiment, the subsea production system further includes a cross over valve connected in parallel with the annulus wing valve which controls flow into the production flow path of the production tree connected to the tubing spool and which is disposed within the production tree. In another embodiment, the subsea production system includes a cross over valve disposed within the annulus tree. The cross over valve in this embodiment is connected in parallel with the annulus wing valve and controls flow into the production flow path of the production tree.
A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings wherein:
The present invention may be susceptible to various modifications and alternative forms. Specific embodiments of the present invention are shown by way of example in the drawings and are described herein in detail. It should be understood, however, that the description set forth herein of specific embodiments is not intended to limit the present invention to the particular forms disclosed. Rather, all modifications, alternatives and equivalents falling within the spirit and scope of the invention as defined by the appended claims are intended to be covered.
The details of the present invention will now be described with reference to the figures. Turning to
Production tree 10 shown in
In one example, the wellhead may be an 18.75 inch wellhead system. In one example, spool 20 may include an upper and lower bore. In one example, wellhead 50 may suspend one casing string. In another embodiment, wellhead 50 may suspend two or more casing strings.
Production wing valve 13 in the example shown in
The region between tubing string 60 and the inner most casing string suspended from casing hanger 51, forms an annular region 56. Some of the embodiments of the present invention separate some or all the annulus flow regions into an annulus block from which annular flow may be controlled. The annular fluid flow within annular region in the embodiment depicted in
The annular wing valve 74 in annulus block 78 controls the annular fluid that flows through annulus flow line 95. For example, if both X/O valve 75 and W/O valve 73 are in the closed position, and if both AM valve 76 and AW valve 74 are in the open position, annulus fluid may flow through annular region 56, through annulus flow path 57, through valves AM 76 and AW 74, and through flow line connector 85 into annular flow line 95. Similarly, access to the annular fluid may be provided through annular flow line 95.
Cross over valve 75 provides additional functionality in the subsea production system. For example, closing valves PW 13 and PS 12 permits the product to flow through PM valve 14 and through cross over line 158. Further, if both valves W/O 73 and AM 76 are in the closed position and both valves X/O 75 and AW 74 are in the open position, product may flow through annulus flow line 95.
Production tree 10 may be removed and replaced with a blow out preventer (“BOP”) during work over. For example, X/O valve 75 and production tree hanger plug 31 may be placed in their respective closed and installed positions, and production tree 10 may be removed from spool 20. A BOP may then be connected to spool 20. With a BOP in place, and W/O valve 73, AM valve 76, and AW valve 74 in their respective closed positions, surface access to the annulus fluid is thereby provided through the BOP choke and kill lines. By placing the annular valves on a base, the annulus fluid may be accessed from an annulus block 78 mounted on a base.
In one embodiment of the present invention, a BOP may be connected directly to the tubing spool 20. For example, the tubing hanger plug 31, and valves AM 76 and W/O 73 may be closed. If a parking stump is included in the subsea production system, the production tree may then be taken off the spool and placed on a parking stump. A BOP may then be connected to the spool. One skilled in the art with the benefit of this disclosure will recognize other valves that may be closed during BOP connection.
Some embodiments of the present invention permit the minimization of the number of valves in a production tree. Additionally, subsea production systems according to the present invention may lack a horizontal outlet from spool 20 and from tubing hanger 30. In some examples, the production tree does not have an annulus bore that traverses through the production tree. Other embodiments of the present invention may provide one or more of the following advantages:
No need for a work over/test tree;
Completion may be run without the control POD or FLC in place.
The present invention may be implemented in various embodiments.
In still other embodiments, the work over valve may be placed within the spool. The examples shown in
BOP stacks typically exert large bending loads to points at and below the connection of the BOP to the subsea production system. In one example, a simple and small tree having a low bending capacity connector on the bottom of the tree may be used. In another example, a BOP adapter may be included in the production systems shown in
In still other embodiments, it may be desirable to have an annulus tree that can be removed and retrieved to the surface.
One skilled in the art with the benefit of this disclosure will recognize other configurations of subsea production systems having a retrievable annular tree. Some examples are depicted in
In still other embodiments, a production tree having a cross over valve 75, a production stab 41, and an annular stab 42 may be used with a retrievable annular tree as shown in
As shown in
The termination of flow path 200 at a point above the tubing spool may be implemented in various embodiments. As shown in
One embodiment of a controls interface for a subsea production system is shown in
The invention, therefore, is well adapted to carry out the objects and to attain the ends and advantages mentioned, as well as others inherent therein. While the invention has been depicted, described and is defined by reference to exemplary embodiments of the invention, such references do not imply a limitation on the invention, and no such limitation is to be inferred. The invention is capable of considerable modification, alteration and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. For example, some configurations may mitigate debris collection in annular flow path. The depicted and described embodiments of the invention are exemplary only, and are not exhaustive of the scope of the invention. Consequently, the invention is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.
This application claims priority to and is a conversion of U.S. Provisional Application Ser. No. 60/553,669 filed Mar. 16, 2004.
Number | Date | Country | |
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60553669 | Mar 2004 | US |