Patent Application
20120241663
The present invention relates to sealing apparatus and methods typically for use in wireline valves, particularly but not exclusively, used in the oil and gas industries. The invention is particularly useful in wireline valves, but can be applied to other situations where it is required to seal the annulus around an elongate member, in apparatus typically called blow out preventers, or BOPs.
Conventionally, wireline valves are used to control wellbore pressure during wireline intervention operations. Wireline valves typically press opposing pairs of ram assemblies against the wireline to provide a double safety barrier against well pressure whilst remedial work is carried out, typically on the wire.
Conventionally, the ram assemblies use resilient (e.g. rubber) seals mounted on the inner faces of two opposing ram assemblies within the wireline valve, to clamp the wireline cable between the seals, thereby containing the pressure. The inner faces of the seals typically have a recess which conforms to the outer surface of the wireline. The ram assemblies and seals move against the wireline cable, typically from opposite sides of the valve, to close off the annulus surrounding the wireline cable. Grease is then typically pumped into and around the wireline cable. The resilient seals are supported by (typically metal) plates in the ram assemblies which retain the resilient seals in place resisting movement of the seals in response to the pressure differential across them. Conventional wireline valves have two pairs of seals, e.g. a pair of upper seals and a pair of lower seals, each seal independently moved by its own actuator (e.g. a hydraulic cylinder in most cases) with a grease chamber between the upper and lower seals, allowing the injection of the grease into the chamber between them when they are clamped against the wireline cable.
In accordance with a first aspect of the present invention, there is provided sealing apparatus for sealing around an elongate member which passes through a throughbore of a valve device, the apparatus comprising an upper sealing element and a lower sealing element, each being adapted to change configuration from an open configuration to a sealed configuration within the valve device to seal the throughbore of the valve device around the elongate member, the upper and lower sealing elements being separate and moveable independently from one another, and being configured to be actuated between open and sealed configurations by a common actuator.
Typically the upper and lower sealing elements are spaced apart on the valve device, typically by a very small clearance, e.g. less than 5 mm.
The change in configuration can be a change in position, e.g. movement, or can be a change in shape. In typical embodiments of the invention, the sealing elements move from one configuration to the other. In some embodiments, the upper and lower sealing elements can be in contact with one another in their open configuration, and can optionally move apart from one another along the axis of the throughbore when changing between the open configuration and the closed configuration. Typically the sealing elements are axially separated from one another by a small distance when grease is injected between them.
Typically the upper and lower sealing elements each comprise a first and second seal, e.g. a left and right seal, which optionally move in the same plane against the elongate member, typically from opposite directions.
The seals are typically housed in ram assemblies, which approach the elongate member from opposite directions, optionally in the same plane, and seal against one another. Therefore, a typical embodiment of the invention could comprise two ram assemblies each ram assembly having two separately movable upper and lower sealing elements.
The invention also provides a ram assembly for a wireline valve, the ram assembly comprising at least two sealing elements, wherein each of the sealing elements are separate and are movable independently from one another, and are configured to be actuated by a common actuator.
Typically the actuator comprises a hydraulic cylinder. Typically the sealing elements engage a stem connected to the piston on the cylinder.
In accordance with a further aspect of the present invention, there is provided a method of sealing around an elongate member which passes through a throughbore of a valve device, the method comprising providing an upper sealing element and a lower sealing element spaced apart on the valve device, and each being adapted to change configuration from an open configuration to a sealed configuration within the valve device to seal the throughbore of the valve device around the elongate member, the upper and lower sealing elements being separate and being movable independently from one another, and actuating the sealing elements between open and sealed configurations using a common actuator.
The upper and lower sealing elements are typically mounted on a common ram assembly on each side of the elongate member.
In a typical embodiment, the first upper and lower sealing elements (e.g. those on the left side) are actuated by one actuator (e.g. one hydraulic cylinder located on the left of the wireline, and the left hand seals are typically engaged by the same stem of the left hand hydraulic cylinder) and the second upper and lower mechanisms (e.g. those on the right side) are typically actuated by a second actuator (e.g. a second, separate stem of a second separate hydraulic cylinder to the first hydraulic cylinder, located on the right side of the wireline).
In some embodiments, a single actuator can be used to activate the two seals, rather than two actuators acting on respective pairs of seals. Where two actuators are used on the same plane, they can be diametrically opposed to one another, or can be arranged at some other angle that is more or less than 180°. In some embodiments, a single seal (with two seal assemblies) can be movable from one side, typically under the force applied by one actuator from that side.
The elongate member is typically a wireline, logging line, cable or the like. In a typical embodiment, the upper and lower sealing elements on each side are arranged on a single common ram assembly, which is actuated by a single respective actuator on each side.
Typically, the ram assembly on each side of the valve can have guide arms to guide and centralise the wireline or other elongate member, and the guide arms can optionally interlock and cooperate with one another to guide the wireline etc into a suitable position relative to the sealing elements for actuation of the actuators to seal with throughbore. Thus each ram assembly (left and right) can have a pair of guide arms, and optionally two pairs of guide arms. Typically, the left and right ram assemblies are arranged substantially diametrically opposite one another about the longitudinal axis of the throughbore. Optionally, the guide arms are arranged about the recess adapted to accept the elongate member therein.
In one embodiment of the invention, each valve has a longitudinal throughbore for receiving the elongate member (e.g. the wireline) and the throughbore has left and right ram housings in the form of lateral ram bores, which intersect with the throughbore and which house left and right ram assemblies that move within the ram bores in a common plane that is perpendicular to the throughbore. Each ram assembly (e.g. left and right) has a pair of sealing elements, upper and lower. Each of the sealing elements typically have a pair of seals, optionally in the form of inner seals at their radially inner faces, to bear against the elongate member to seal off the throughbore, and an outer seal typically housed in a groove, which can be annular or partially annular, and which typically seals the annulus between the ram bores and the ram assemblies. Typically the inner and outer seals on each sealing element connect to complete the seal. However it is not necessary for the seal on each side to move, and in some embodiments only a single seal on one side is movable.
Typically the ram assemblies and optionally the sealing assemblies are resistant to rotation within the ram bores. Typically the ram assemblies and optionally the sealing assemblies are non-circular, and thereby resist rotation.
In one embodiment, at least one of the sealing elements (and typically both of them) is movable relative to the common actuator, and this is typically achieved by a constraining connection between the actuator and the sealing elements.
As one example of a constraining connection between the sealing elements and the actuator, the radially outermost end of each of the ram assemblies in one embodiment typically each have an axial channel, groove or slot in which a portion of the driver (e.g. a head or pin) is captive, but is constrained to move axially along the length of the channel, groove or slot, which can typically be co-axial with the axis of movement of the sealing element. The driver portion can only move within the confines of the slot, and is typically axially shallower than the slot, so as to allow relative axial movement between the two, but to restrict or deny relative lateral and optionally rotational movement. In one embodiment, the portion of the driver can comprise a T-shaped head of part of the actuator, and the head can be located in the channel, groove or slot. A typical actuator comprises a hydraulic cylinder, usually located within the ram bore, but the particular design of actuator is not important, and a mechanical screw actuator can be used instead of a hydraulic cylinder if desired.
The channel on the radially outermost end of the ram assembly typically accepts captive portion that is optionally in the form of a T-shaped head on the stem of the hydraulic cylinder, and retains the T-shaped head within the channel by means of a lip on the inner surface of the channel, which prevents the T-shaped head from pulling out of the channel. The channel can be a simple recess formed in opposing faces of the upper and lower sealing elements of the ram assemblies, and the recesses on each of the upper and lower sealing elements can typically align to form the channel between them, thereby allowing them to be assembled around the head of the stem and retain the head in the channel.
The channel typically can have a neck to receive the stem, and the neck can have a narrower diameter than the head, thereby allowing passage of the stem through the neck but retaining the head within the confines of the channel. The depth of the channel in the axial direction of movement of the head typically has a greater dimension than the depth of the head, so the head can travel within the channel for a small distance before abutting the neck at the outboard end of the channel or the wall of the sealing element at the inboard end of the channel. The desired limitations to movement in each case are typically related to the resilience and size of the inner seal, and the axial distance that the head can move within the channel is different depending on the different characteristics of the inner seal, which can vary in different cases and is not intended to be a limiting feature of the invention. For example, in some cases, for example with small seals adapted to hold a slim wireline with a very narrow bore, the axial distance of travel of the head of the stem can be e.g. 2-3 millimetres, but in larger valves with larger and/or more resilient seals, the axial distance of travel can be e.g. 10-15 mm.
The channel is typically formed from two machined semi-circular recesses in the outer ends of the bodies of the sealing elements, which cooperate to form the channel, and retain the head of the stem. The body of either one of the two sealing elements can therefore move independently of the other on the ram assembly, relative to the actuator, while the other remains stationary and engaged with the T-shaped head of the stem. Accordingly the sealing elements can react independently of one another to pressure differentials across the seals, by means of the loose fit of the actuator and the ram assembly. The loose fit of the stem in the channel is typically restrained so that the sealing elements are not entirely free to move in every plane, and the range of movement is typically restricted, e.g. to axial movement of the sealing elements relative to the stem, in the direction of movement of the stem during actuation. Typically the sealing elements are captive in ram bores and are restrained to move only along the axis of the bores, which is typically parallel with the axis of the actuator movement during actuation.
Typically the sealing elements comprise seals mounted on seal bodies to support and orientate the seals. The seal bodies typically have outer faces to engage the inner surfaces of the ram bores, and typically have mating faces, which can be flat, and which can optionally be keyed together e.g. splined in some embodiments, to guide sliding movement of the sealing elements with respect to one another. The seal bodies typically have grooves formed in the mating faces to form the channel to receive the head of the stem. In certain embodiments of the invention the seal bodies can have grease channels extending axially (e.g. parallel to the ram bore) from the inner end of the seal bodies to the outer end of the seal bodies to provide an axial channel for the injected grease to pass from the outboard face of the sealing elements typically between the seal body mating faces in order to reach the wireline clamped between the inner seals. The axial grease channel can optionally comprise an axial groove formed in one of the mating faces of the seal bodies, or can optionally be provided in both faces, and in that case, optionally the two grooves can then be superimposed on one another to form a larger conduit for the grease. The grease channel can optionally terminate in the groove that receives the stem. A grease channel can optionally be provided in one or in each of the seal bodies. The grease channel typically provides a path of little resistance to the grease injected behind the sealing elements, to allow effective penetration of the wireline cable trapped between the inner seals. Of course, grease can optionally be injected freely between the sealing bodies without any particular grease channel being provided.
The apparatus typically has a grease injection device to inject grease between the upper and lower sealing assemblies. The injection pressure of the grease typically applies additional pressure on the sealing elements to energise the seals, and can typically move one or both of the sealing elements relative to the stem and/or relative to the other sealing element.
The upper and lower sealing elements are typically oriented in different directions, to withstand pressure differentials in different e.g. opposite directions.
Actuating the upper and lower sealing elements from a common actuator reduces the stack height and the weight of the valve, and reduces the number of well seals.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:—
The valve V has a body 1 shown in sectional view in
The ram assemblies 5 in the left and right bores are substantially similar to one another, and are pushed axially through the ram bores 3 by actuators. In this embodiment, the actuator is in the form of a stem 6 that is moved axially through the ram bore 3 by a suitable driver, such as a hydraulic cylinder 4. The particular type of driver is not important, and embodiments of the invention can function satisfactorily with mechanical or other drivers, e.g. those relying on screw threads. The stem 6 has a head 6h.
Each ram assembly 5 has an upper sealing element 10 and a lower sealing element 20, as shown in
The upper sealing element 10 has a body 12 of generally semi-cylindrical shape, with an axis that is generally parallel with an axis of the ram bore 3 in which it is housed. In this particular embodiment, the bodies 12 and 22 have generally semi-oval shapes, as is best shown in
The body 12 also has an inner seal slot 15, which houses an inner seal 17 at its axially inner end, so that the inner seal 17 is located closest to the throughbore 2 of the valve 1. The inner seal 17 is optionally bounded by two metal plates which are bonded to the rubber portion during the manufacturing process, although a simple rubber block can suffice. The inner seal 17 in this embodiment is supported above and below by metal plates which place limits on the extent to which the seal 17 can deform during exposure to pressure differentials, and in this embodiment is fixed to the plates via bolts or other fixings. The innermost face of the inner seal 17 has a recess 18 which is arranged to be perpendicular to the longitudinal axis of the cylindrical ram body 12, and which is arranged to be aligned with the axis of the throughbore 2 in use.
Optionally, the body 12 has wireline guides 19 at its inner end providing inter-engaging “V” shaped guiding formations which guide a wireline into the recess 18.
At its outer end, opposite the inner seal, the body 12 has a recess, which is typically in the form of a slot or groove or channel. In this case, the recess 13 extends axially in alignment with the axis of the stem 6. The recess 13 is machined in the flat lower face, and typically has two portions, a deep groove with a wide diameter, and a lip with a restricted diameter (typically less than the diameter of the head 6h of the stem 6).
The lower sealing element 20 has a similar cross section to the upper sealing element, and has a body 22 of generally semi-cylindrical or semi-oval shape of steel or another metal which supports the seals. The body 22 has an arcuate lower face having a partially circumferential seal slot 24 into which an outer seal 26 is located. Like the seals on the upper sealing element 10, the outer seal 26 on the lower sealing element 20 extends around the arcuate lower surface of the body as shown in
The body 22 also has an inner seal slot (similar to seal slot 15) which houses an inner seal 27 at its inner end, relative to the ram bore 3, located closest to the throughbore 2 of the valve 1. The inner seal 27 typically has the same construction as the inner seal 17.
Optionally, the body 22 has wireline guides 29 providing “V” shaped guiding formations which guide a wireline into the recess 28. The guides 29 typically cooperate with the guides 19 in the upper sealing element 10 to guide the wireline into the recesses 18 and 28, which align with one another to seal around the wireline or other elongate member.
As can be seen from
The lower body 22 also typically has a recess 23 in alignment with the axis of the stem 6 at its radially outer end, and in alignment with the recess 13 in the upper sealing element body. The recesses 13 and 23 combine to form a bore to receive and retain the head 6h of the stem 6 at the outer end of the sealing elements 10, 20. The bore is formed by the juxtaposition of the semi-annular recesses 13, 23 in the symmetrical upper and lower sealing bodies 12, 22.
The left and right ram assemblies 5 each comprising the upper and lower sealing elements 10, 20 are placed within the respective ram bores 3 on the left and right of the wireline valve 1, and in normal operation of the wireline valve, the pair of ram assemblies 5 will be located in the position shown in
The left and right rams 5 approach one another under the force applied via the stems 6, as shown in
The ram assemblies 5 continue to move toward one another until the inner seals 17, 27 are pressed together, which also presses the outboard ends of the inner seals 17, 27 against the adjacent ends of the outer seals 16, 26. Thus, the leak paths surrounding the upper port 5u are sealed by the seals 16, 17 on the upper sealing element 10 and the lower port 5l is sealed by the seals 26, 27 on the lower sealing element 20, and in each case the inner and outer seals connect to completely seal around the port, thus ensuring that the pressure in the wellbore below the wireline valve is retained by two complete (upper and lower) barriers.
The grease is typically injected between the upper and lower sealing elements 10, 20 under high pressure, typically at a higher pressure than the wellbore pressure than the valve is rated to contain. For example, where the wireline valve is rated at 10 kpsi, it is used where the wellbore pressure is typically less than this, and a typical wellbore pressure for such a valve might be around 8 kpsi. The grease is typically injected into the ram bore 3, behind the outer seals 16, 26 at a pressure that is around 10-20% higher, e.g. 10 kpsi. The stem 6 is not sealed to the ram assemblies 5, so grease is squeezed into the space between the inner seals 17, 27 and into the leak paths within the many strands of wire in the wireline cable. Typically the sealing elements 10, 20 are initially touching or are closely adjacent to one another in the open configuration, but as the grease is injected in the closed configuration the sealing elements 10, 20 are typically pushed axially apart from one another by the injection of the grease, by a small distance related to the tolerance of the ram assemblies 5 within the ram bores 3. This is advantageous, as it allows the creation of a small grease chamber between the seals.
Therefore, the pressure differential across the two sealing elements 10, 20 is not equal, because the conduit immediately below the valve 1 is at 10,000 psi, and the conduit immediately above the valve 1 is at atmospheric pressure, so the upper sealing element 10 is exposed to a far greater pressure differential than the lower sealing element 20.
Therefore, when the sealing elements 10, 20 are sealed against the wireline and the grease pressure is applied to pump the grease into the wireline and close the leak paths between the upper and lower ports 5u, 5l, the inner seals 17, 27 are able to move axially within the ram bores 3 in accordance with the pressure differential to which they are exposed. The force applied to the lower sealing element 20 by the moderate pressure differential across the lower sealing element 20 is not usually sufficient in normal wellbore conditions to overcome the reaction force of the resilient inner seal 17 reacting to the pressure of the head 6h of the stem 6 against the lower body 22. Therefore, under normal conditions, the head 6h remains pressed hard against the radially outer end of the channel 13 while the inner seal 27 on the lower sealing assembly is kept pressed against the wireline cable and against the opposing inner seal 27. However, since the throughbore pressure immediately above the wireline valve V is much lower than the pressure below it, and since the same grease pressure is applied to bore the upper and the lower sealing elements 10, 20, the upper sealing element 10 is exposed to a much higher pressure differential than the lower sealing element 20. Therefore, the same grease pressure behind the outer seals 16, 26 applies more force to the upper sealing element 10 than to the lower sealing element 20. The force applied to the upper sealing element 10 by the pressure differential is higher than the force applied by the hydraulic cylinder 4 and stem 6, and so the upper sealing element 10 is pressed axially against the wireline cable not by the hydraulic pressure but by the pressure differential between the injected grease and the bore immediately above the wireline valve V.
One benefit of the present arrangement is that in the event of transient wellbore pressure spikes below the valve, the high pressure kick below the valve increases the pressure differential applied to the upper sealing elements 10, and this causes the upper seals to move closer together as shown in
Modifications and improvements may be made to the foregoing embodiments with departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0915085.5 | Sep 2009 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB2010/051438 | 9/1/2010 | WO | 00 | 5/23/2012 |
