The present invention relates to a packer actuation system for a blowout preventer (BOP). For example, a blowout preventer for use in the drilling of a wellbore, which may be in to a subterranean fluid reservoir and/or the production of fluid, typically hydrocarbon fluids, from such a reservoir.
The drilling of a borehole or well is typically carried out using a steel pipe known as a drill pipe or drill string with a drill bit on the lowermost end. The drill string comprises a series of tubular sections, which are connected end to end. The entire drill string is typically rotated using a rotary table mounted on top of the drill pipe, and as drilling progresses, a flow of mud is used to carry the debris created by the drilling process out of the wellbore. Mud is pumped down the drill string to pass through the drill bit, and returns to the surface via the annular space between the outer diameter of the drill string and the wellbore (generally referred to as the annulus). For a subsea well bore, a tubular, known as a riser, extends from the rig to the top of the wellbore and provides a continuous pathway for the drill string and the fluids emanating from the well bore. In effect, the riser extends the wellbore from the sea bed to the rig, and the annulus also comprises the annular space between the outer diameter of the drill string and the riser.
The use of blow out preventers to seal, control and monitor oil and gas wells is well known, and these are used on both land and off-shore rigs. Blowout preventers are generally arranged in combinations that include ram-type and annular BOPs, connectors, valves, and control systems that enable actuation of the various pressure control functions. These combinations are called BOP stacks. During drilling of a typical high-pressure wellbore, the drill string is routed through a BOP stack toward a reservoir of oil and/or gas. The BOP is operable to seal around the drill string, thus closing the annulus and stopping flow of fluid from the wellbore. The BOP stack may also be operable to sever the drill string to close the wellbore completely. Two types of BOP are in common use—ram and annular, and a BOP stack typically includes at least one of each type.
Blowout preventers (BOPs) were developed to cope with extreme erratic pressures and uncontrolled flow emanating from a well reservoir during drilling. Known as a “kick”, this flow of pressure can lead to a potentially catastrophic event called a blowout. In addition to controlling the downhole well pressure and the flow of oil and gas, blowout preventers are intended to prevent tubular goods used in well drilling, such as, drill pipe, casing, collars, tools and drilling fluid from being blown out of the wellbore when a kick or blowout threatens. Blowout preventers are critical to the safety of crew, drilling rig, and environment, and to the monitoring and maintenance of well integrity; thus blowout preventers are intended to provide an additional and fail-safe barrier to the systems that include them.
Annular blowout preventers can be used as a part of a subsea BOP stack in order to enable an immediate response to a kick. Annular preventers can close on a wide variety of drill string elements such as tool joints, collars, casing etc. so that it is not necessary to determine which element of the drill string is located inside the annular BOP before closing it. Ram type BOPs can only close on a restricted range of drill string elements, so that it is necessary to take the time to determine what part of the drill string is located inside the ram BOP before closing it. Annular BOPs may also enable BOP coverage for drill string elements which would not be practical to cover with a combination of ram type BOPs. Annular BOPs may also enable moving the drill string while sealing the annulus between the drill string and the well bore, which is desirable in certain well control operations.
Related solutions in the field of annular blow out preventers which may be useful for understanding and practicing the present invention include US patent documents U.S. Pat. Nos. 3,572,627, 3,897,038, 4,099,699, 4,458,876, 4,579,314, 3,994,472, 3,915,424, 3,915,426, 4,458,876, 4,460,151, 4,007,904 and 3,915,425.
BOPs are safety-critical components and there is a continuous need for solutions which improve the reliability and operational performance of such systems. Moreover, when BOPs are used subsea it is very time-consuming and expensive to pull the BOP to the surface for maintenance. It is therefore an object of the present invention to provide an annular blow out preventer having a structure that provides improved performance compared to known solutions.
According to a first aspect of the invention, we provide a packer actuation system for a blowout preventer, comprising:
a packer arrangement having an axial passage therethrough;
an actuation system which is releasably mechanically connected to the packer arrangement;
wherein the actuation system is operable to move the packer arrangement from an expanded position to a contracted position such that a dimension of the axial passage decreases, and the actuation system is operable to move the packer arrangement from the contracted position to the expanded position such that the dimension of the axial passage increases.
According to a second aspect of the invention, we provide, a blowout preventer of the type having a resilient packer element comprising a contractor arrangement which has a plurality of plates adjacent one another which enclose an area, the contractor arrangement is configured to move from an expanded position to a contracted position in which the enclosed area decreases, wherein adjacent plates are configured to interlock with one another when in the contracted position.
In a further aspect of the invention, there is provided a packer actuation system for a blow out preventer, comprising: a packer arrangement having an axial passage therethrough; an actuation system comprising a movable actuation element, the actuation system operable to move the packer arrangement via the movable actuation element from an expanded position to contracted position such that the dimension of the axial passage decreases; a position sensor arranged to measure the position of the movable actuation element.
In a further aspect of the invention, there is provided a method for determining the condition of a packer arrangement for an annular blow out preventer, comprising the steps: (a) providing a packer actuation system; (b) actuating the packer actuation system; (c) reading a position value of a movable actuation element measured by the position sensor; (d) comparing the position value to a pre-determined, nominal position value.
Further features of embodiments of the invention are set out in the appended claims.
Embodiments of the present invention will now be described, by way of example, with reference to the drawings in which:
The basic functionality of an annular blow out preventer (BOP) is well known in the art and will not be more detailed here. Reference is made to the above mentioned patent documents.
An annular BOP according to one embodiment of the present invention may have a sealing element contained within an external housing, referred to as the packer or packing element, and a double-acting hydraulic actuator mounted within or connected to the housing. The actuator, for example in the form of a piston/cylinder arrangement, forces the annular sealing element inwards via a plurality of pusher plates, until it engages with the external surface of the drill pipe positioned in the BOP's internal passageway (also known as a bore). Releasing the pressure on the actuator, or actively driving it in the radially outwardly direction, releases the force from the pusher plates on the sealing element, thus allowing the element to relax to its original position away from the drill pipe body.
In the embodiments described here, the actuators are hydraulic piston/cylinder arrangements, however the actuators may be of any type, for example electro-mechanical or pneumatic actuators.
In the embodiment shown in
The contractor arrangement 230 includes a plurality of arcuate/curved plates (also called pusher plates) 204 positioned adjacent one another. Each piston stem 203 is connected to a respective pusher plate 204 (see also
At each intersection between two pusher plates 204, there is a packer retractor mechanism 500 (also called a packer retraction linkage 500). The retractor part 104 is connected to the packer retractor mechanism 500. As can be seen from
In the embodiment shown in
As can be seen in
Therefore under the action of the actuators 200, the pusher plates 204 will interweave so as to form a continuous ring shaped element around the packer arrangement 100.
During closing of the blowout preventer, there is lateral engagement between adjacent pusher plates 204 and the pusher plates 204 contact the outside diameter of the resilient packer element 101. In conventional designs, this action may cause damage to the outside diameter of the packer element 101 during repeated open and close cycles, as a portion of the packer element 101 is pinched between adjacent pusher plates 204. The lateral engagement in this construction reduces damage to the packer element 101 by means of the overlapping engagement protrusions 401, 402, 403404. Thus, during closing, the protrusions 401, 402, 403, 404 overlap those of the adjacent plates 204 so that the plates interweave/interlock and form a continuous ring shape element around the packer element 101. The pattern of the protrusions 401, 402, 403, 404 provides synchronized movement of the plates 204. This also provides a more robust synchronization of the actuator pistons 202 than, for example, the dowel pins known from conventional designs. For example, one known design uses dowel pins protruding from one side of each pusher plate to engage holes in the opposite side of each pusher plate.
As mentioned above, the packer actuation system further comprises a retractor arrangement 240. The retraction arrangement 240 includes a packer retraction mechanism 500 and the retractor parts 104.
The packer retraction mechanism 500 of the present invention is also provided with a third connection formation (also known as a third fixation point) 501 to be attached to a retractor part 104 which is connected to one of the packer insert 102 disposed within the packer element 101 of the blowout preventer. The retractor part 104 extends radially outwardly of the packer element 101 generally perpendicular to its axial passageway 211. A first end of each retractor part 104 is pivotally connected to the packer insert 102, whilst a pin 106 is provided at the other end of the retractor part 104. The pin 106 extends generally parallel to the axial passageway 121 of the packer element 101, and is used to connect the packer element 101 to the packer retraction mechanism 500, as will be described further below.
The first central pivot point 509c is located in the central part of the second and third portions 502, 505 and allows these two portions to slide against/move relative to each other. The second and third portions 502, 505 are each pivotally connected to a pusher plate 204a, 204b on one end such that when the two portions slide against each other, the adjacent pusher plates 204a, 204b are displaced in a direction perpendicular to the pivoting axis of each pivot point.
The second and third portions 502, 505 are also each pivotally connected to a leg 503, 504 of the first portion 507 on their other end such that when the legs of the first portion 507 pivot about the hole 501, this forces the second and third portions 502, 505 to pivot about the central pivot point 509c, and thus displace the adjacent pusher plates 204a, 204b in a direction perpendicular to the pivoting axis of each pivot point.
It should be appreciated that in this embodiment the packer retraction mechanism 500 is connected to the pusher plates 204, but this need not necessarily be the case. The packer retraction mechanism 500 could be connected directly to an actuator 200 and move independently of the pusher plates 204.
In this embodiment, each packer retraction mechanism 500 is installed in between two adjacent pusher plates 204a and 204b (pusher plates shown flat for simplicity) and comprises a pantographic mechanism having articulated linkages between the pusher plates 204a, 204b. The two adjacent pusher plates are thus linked by a pantograph mechanism in an articulated manner that permits them to move, in a limited way, one towards the other when pushed by the actuators 200 or one away from the other when retracted by the actuators 200. When the separation of the pusher plates 204 increases, the separation of the pivotal connections 509b, 509d between the leg 503, 504 and its respective second 502 or third 505 portion also increases. Thus, the legs of the first portion 507 pivot away from one another, so that the hole 501 moves towards the pusher plates 204. This is illustrated in
As mentioned above, each packer retraction mechanism 500 is also provided with an opening 501 (i.e. the opening 501 of the first portion 507) and, in use, this engages with the fastening means/connection part 106 of a retractor part 104. Thus, the packer inserts 102 of the annular packer element 101 and the pusher plates 204 are linked together so that their movements are interrelated.
During closing, i.e. going from the state in
As the pusher plates 204 are forced to retract by the actuators 200 upon opening the BOP, the packer retraction mechanism 500 engage with the inserts 102 via the retractor part 104. The packer inserts 102 (that are embedded within the packer element 101) are pulled radially outwards and fully open the packer element 101.
In this embodiment, the engagement of the retractor part 104 and the retraction mechanism 500 (e.g. the pin 106 through the opening 501) may take place when the packer element 101 is lowered (with the packer element 101 arranged so that the pin(s) 106 extends downwardly from the end of the retractor parts 104) into the BOP housing during installation, so that the pin 106 of each retractor part 104 slides into the opening 501 of one of the packer retraction mechanisms 500.
According to the invention, there is thus provided means to actively retract the packer arrangement 100 to the fully open position. Conventionally annular BOPs rely on the strain energy stored in the resilient packer element to provide the force necessary to urge the packer arrangement to the fully open position. Cold weather or loss of elasticity in the rubber due to fatigue can slow this opening process significantly, or can cause the BOP to fail to fully open. The new structure described here permits the use the BOP operating system to urge the packing to the fully open position in a positive and expeditious manner. A further advantage is the ability to use elastomer materials which are very durable, but which lack sufficient elasticity to fully open within a practical time interval.
Another advantage provided by an embodiment of the current invention is that the packer arrangement 100 is releasable from the actuation system. The pins 106 can simply slide out of the openings 501 in the packer retraction mechanisms 500 as the packer element 101 is lifted up. Since the resilient material of the packer element 101 is more prone to damage and/or wear that the actuators 200 and/or the contractor arrangement 230 and/or the retractor arrangement 240, it is advantageous to be able to replace the packer arrangement 100 without needing to replace the other parts at the same time.
In all embodiments described the packer inserts 102 are preferably made of metal but could also be made of any resistant material rigid enough to resist the environment of and the retractable force exerted by the actuators 200 on the pusher plates 204 and packer retraction mechanism 500 and thus on the packer inserts 102. It should be appreciated that the contractor arrangement 230 (e.g. the pusher plates 204) and the retractor arrangement 240 (e.g. the retraction mechanism 500) may also be made of metal.
In a further aspect of the invention, illustrated in
By means of the position sensor 600, it is possible to identify, at any desired time, the position of the actuator, and thereby the position of a packer in the annular blow out preventer. The sensor readings from the sensor 600 can be transmitted via a signal cable 604 to a computer system 605 for storage, display or processing, as illustrated schematically in
Having a position sensor 600 arranged as described above allows monitoring of BOP functionality at all times, as well as using the sensor data to obtain information about the reliability and operational state of the BOP. For example, it is possible to establish with more certainty that the annular BOP has reached the fully open position after having been closed, which is important for example when entering large tools down into the wellbore. Such tools may otherwise get stuck, or even damage the tool or the BOP, if the annular BOP is not correctly opened.
The position sensor 600 can be used to obtain an indication of packer wear. When the packer is in service over a period of time, the resilient material will wear, particularly at its inner circumference. This may require the actuator to provide a longer stroke in order to fully close the BOP. By comparing the actual closing stroke or actuator end position, to a nominal value, an indication can be obtained as to whether the annular BOP requires replacement and whether it is fit for continued service.
The position sensor can thus be used for determining the condition of a packer arrangement for an annular blow out preventer, by actuating the packer actuation system to close on either a drill pipe of known diameter or on itself (i.e. without a drill pipe extending along the central passageway 211 through the packer element 101), then reading a position value of the movable actuation element measured by the position sensor 601, and comparing the position value to a pre-determined, nominal position value. If a longer actuation stroke than the nominal value is required, then that can be taken as an indication that the packer element is worn. The difference between an actual stroke length and a nominal value may provide an indication of how much the packer element is worn.
The process of reading the end position of the actuator in the closed state, either with the annular BOP closed on a pipe of known diameter (such as drill pipe) or on itself can be repeated on a plurality of occasions over time, and the measured position value recorded on each occasion. The resulting data can be used in the creation of a position measurement over time graph, as illustrated in
Further, by comparing subsequent readings of the closing displacement, a time tm when the packer element would need replacement can be predicted. This is illustrated in
Computer system 605 may be programmed to output a warning signal (visual or audible) to alert an operator if the latest position reading suggests that the packer element 101 is so worn that it requires replacement, i.e. being close to or higher than xm. In this case, the computer system may be configured to issue a series of staggered warnings—for example, an yellow warning when the packer element 101 has worn by a first pre-determined amount, an orange warning when the packer element 101 has worn by a second, greater, pre-determined amount, and, as such, the need for replacement is imminent, and a red warning when the packer element 101 has worn by a third, even greater, amount and needs immediate replacement.
Computer system 605 may, alternatively or additionally, be programmed to output a remaining useful lifetime value, a wear rate value, and/or a predicted time for maintenance value, tm, to an operator. The wear rate may be calculated based on a development in the packer wear readings, e.g. as a function of the slope shown in
Thus, by means of a system and/or method according to aspects of the present invention, such replacement and maintenance of the BOP can, for example, be better planned in advance and, for example, combined or coordinated with other maintenance activities.
According to aspects of the present invention, the operational integrity of such safety critical components as annular blow out preventers may therefore be ensured and predicted in a better way.
When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.
The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.
Number | Date | Country | Kind |
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20160506 | Mar 2016 | NO | national |
20160507 | Mar 2016 | NO | national |
20160508 | Mar 2016 | NO | national |
Filing Document | Filing Date | Country | Kind |
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PCT/NO2017/050074 | 3/28/2017 | WO | 00 |