GB2541005A - Well abandonment frame, cartridge and method of carrying out abandonment operations - Google Patents

Abstract

A well abandonment frame 18 for fitting over a well head to facilitate abandonment operations, comprising a plurality of upwardly extending load bearing legs 19 and a plurality of junction joining members 31 joining said legs to said frame; said junction members comprising an aperture being defined by a rim 28 for engagement with cartridges to facilitate a plurality of abandonment operations. The well abandonment frame may incorporate a plurality of concentric rims which may comprise a lower rim 30, an intermediate rim 29 and an upper rim 28. The frame may incorporate a means for adjusting said legs, and said legs may incorporate mud mats and a means for vertically displacing said mud mat. The legs may incorporate a pile which may be driven into the bed on which the frame is mounted.

Description

WELL ABANDONMENT FRAME, CARTRIDGE AND METHOD OF CARRYING OUT ABANDONMENT OPERATIONS

Field of the Invention

The invention relates to well abandonment frames for fitting over a well bead to facilitate one or more abandonment operations, cartridges for securing to a well abandonment frame and methods of carrying out abandonment operations on a well head, β§.ν.!ίί£»?^ A number of companies are considering the process involved in abandoning wells that were originally drilled in the early 19d0’s. During this period, subsea devices were in their infancy, as such they did not meet the modern standards for heavy duty connection types and did not have the capacity to support loads of the kinds seen through modem blow out preventers (so called BOP’s), These abandoned wells are also affected by severe loss of structural strength due to long-term corrosion and are therefore highly sensitive to lead. There is also a lack of fatigue history and material information for such subsea structures requiring rebofirtshle devices which can withstand virtually all the weight arid loading equipment used during the abandonment and transfers to the seabed via the structure’s foundation. The structures witch are envisaged in certain embodiments of the invention may he specifically designed to restrict andior control the loads imparted into the particularly load sensitive wells. There is also a requirement to provide structures which1 lend themselves to modular assembly and disassembly, The structures must also be able to withstand harsh surrounding environmental conditions such as water currents and the irregularity of the profile of the seabed in question.

Summary of the invention

In a first broad independent aspect, the invention provides a well abandonment frame for fitting over a well head to facilitate one or more abandonment operations comprising a plurality of upwardly extending l|§d bearing legs and a plurality of junction members joining said legs to form said frame; said junction members presenting an aperture through which said abandonment operations fixe carried out; said aperture being defined by a rim for engagement with one or a succession of cartridges w'hich are secured to facilitate one or a plurality of abandonment operations.

This configuration is particularly advantageous because it allows the aperture in certain embodiments to potentially entirely clear and thus avoid contact with the well head which is destined for abandonment and ultimately removal. It is also particularly advantageous because it allows a plurality of load inducing devices to be fitted to the structure for the completion of a plurality of well head abandonment operations.

In a subsidiary aspect, the rim is circular·. This provides the optimum configuration for the centralisation of the cartridges onto the frame,.

In a further subsidiary' aspect, the frame incorporates a plurality of concentric rims. These provide an optimum level of structural strength whilst allowing the tree of the well head to be cleared and positioned centrally relative to the frame itself in a further subsidiary aspect, the frame incorporates not only a plurality of concentric-rims but these are arranged so that a lower rim, an intermediate rim and an upper run are provided where die intermediate rim has a diameter which is lower than both the diameter of fire upper and lower rims. Ibis configuration is particularly advantageous because it provides the succession of rims or rings with a so-called hourglass configuration whson allows optimum placement of the frame onto and around the well head structure. In particular the lower rim’s diameter allows sufficient clearance to cope with the almost unavoidable effect of currents and waves on the lowering process of the frame onto the seabed. The intermediate rim allows optimum centralisation of the frame relative to the well head which is destined tor abandonment which facilitates optimum completion of the abandonment operations. The upper rim is also particularly advantageous since it facilitates the interface between a cartridge for the execution of abandonment operations.

In a further subsidiary aspect, the legs Ippprporate means for adjusting the length of the legs. This configuration is particularly advantageous in order to allow the frame to cope with unevenness in the relief of the seabed surrounding tie well in need of abandonment.

In a further subsidiary aspect, the legs incorporate a mud mat and means for vertically displacing the mud mat. This configuration is particularly advantageous in. order to allow the load carried by the legs to be spread over a large surface area of the seabed.

In a further subsidiary aspect, one or more of the legs incorporates a longitudinal, tunnel and accommodates a pile which may be driven into the bed on which tire frame is mounted. This allows the frame to be secured to the seabed not only via the legs themselves but optionally with the extra security provided by a plurality of piles which may be driven into the seabed. hi a further subsidiary' aspect, the upper aperture of the longitudinal tunnel incorporates a funnel This allows advantageously the piles to be more readily centralised into the tunnel gf the legs for more straightforward assembly.

In:» further subsidiary aspect, the legs incorporate a plurality of locks for locking fee legs onto the pile. This configuration further reinforces fee structural strength and stability of fee frame when secured to the seabed. In addition, it prevents upward movement of the frame relati ve to fee pile. l a further apect, fee invention provides a cartridge for securing to a well abandonment frame according to any of the preceding aspects, the cartridge comprises in this further aspect a rim for securing to fee upper rim of a frame according to a preceding aspect and a plurality of downwardly extending guide rods for centralising fee rim onto fee upper rim. This configuration is particularly advantageous in terms of achieving an optimum interface between a cartridge and the well abandonment frame. It also provides a mechanism for centralising the engagement of the respective rims or rings.

In a further subsidiary aspect, fee rim incorporates a plurality of dampers for engaging fep upper rim. This configuration is particularly advantageous for controlling fee engagement of fee respective rims of fee cartridge and of the frame. This configuration will avoid or significantly minimise any mechanical impact or vibration which could affect the success of the abandonment operations,

In a further subsidiary aspect, the dampers are adjustable in height by remote control.

This configuration is particularly advantageous in order to control fee lowering of the dampers in order to achieve a particularly advantageously stable engagement of the cartridge and fee frame, in a further subsidiary aspect, the cartridge further comprises a locking mechanism. This allows advantageously the respective rims to be engaged in an interfacing manner in an advantageously secure manner.

In a further subsidiary aspect the cartridge further comprises an arm for locking the cartridge onto the upfp” rim. This configuration is particularly advantageous In terms of tlie tensile load that may he carded by the arm whilst achieving advantageous immobilisation of one rim relative to the other for successful and potentially successive abandonment operations.

In a. further subsidiary aspect, the cartridge further eompilses a locking jaw which clamps mro the upper rim. Tills configuration is particularly advantageous since it allows the securing of the cartridge onto the feme whilst reducing the required complexity of operation when compared to the aim locking mechanism in the preceding aspect.

In a farther subsidiary aspect, the cartridge ipther comprises means for emrppg out a workover operation.

In a farther subsidiary aspect, the cartridge further comprises a well head extensipp. fo a fiirther aspect, the in vention provides a well Jbandonraent system which comprises a frame according to the preceding aspects and % cartridge according to certain preceding aspects relating to cartridges.

In a farther subsidiary aspect, the system handles a well head which has guide posts whilst die system further comprises a guide feme for securing to the well head’s guide posts. This configuration is particularly advantageous in terms of further minimising potential contact with the weakest areas of the well bead in need of abandonment.

In a farther aspect, the invention provides a method of carrying out. abandonment operations on a well head comprising the steps of providing a feme according to any of the preceding aspects, posiiomng the frame aSsulthe well headland carrying out one or more operations by employing one or a succession of cartridges according to any appropriate previously mentioned aspects.

In a farther subsidiary aspect, the well head incorporates guide posts and the method further comprises the step of securing a guide hams to the guide posts. This method, is particularly advantageous because it facilitates an initial attachment to parts of the well head which are less susceptible to failure. in a further subsidiary aspect, the frame incoraorates mod mats and the method further comprises the step of remotely controlling the position of the m ud mats. Thi s allows the frame to appropriately distribute the loads onto a potentially uneven seabed.

In a further subsidiary aspect, the method further comprises the steps of locking one or a succession of the cartridges to the frame. This is particularly advantageous in terms of optimising the distribution of load onto die frame in order to avoid and minimise any load carrying of die well head itself.

Brief Description of the Figures

Figure 1 shows a perspective view of a well head in need of removal and abandonment.

Figure 2 shows an embodiment of the process of initially securing a guide frame to the guide posts of a well head .

Figure 3 shows a perspective viip of ag|dde frame in the proems of bdngsecmed to Ise guide posts of a well. head.

Figure 4 shows a guide frame secured to the guide posts of a well head.

Figure 5 shows a perspective view of a well abandonment frame feeing lowered onto and about a well head and its accompanying structure,

Figure 6 shows a well ^undonipni flame positioned over ftp well head prior to the deployment of mud mats and prior to any optional pil ing.

Figure 7 shows the lowering of the well abandonment feme onto the well head.

Figure 8 shows a perspective view of a well abandonment feme with a plurality: of piles: being inserted through the tunnel of the respective legs.

Figure 9 shows a perspective view of the well abandonment frame with a plurality of pies secured to the seabed and with the mud mats deployed.

Figure llAows a side elevation, of the lowering of a first cartridge onto the feme.

Figure 11 shows a perspective view' of the lowering of a first cartridge onto the frame.

Figure 12 shows a perspective view of the upper rim of the feme about to engage the corresponding rim of the cartridge.

Figure 13 shows the initial engagement of the upper rim of the frame with the various dampers of the cartridge.

Figure 14 shows a first configuration of a locking mechanism in perspective view.

Figure 15 shows a perspective view of a further locking mechanism.

Figure 16 shows the positioning of a workover station in perspective view.

Figure ! 7 slows the removal of the first cartridge and the removal of the tree of the well head.

Figure 18 shoves a perspective view of the removal of the first cartridge with the tree of the well head,

Figure if slows the deployment of a second cartridge onto the well abandonment frame.

Figure 20 show's a perspective view of a second cartridge,

Figure 21 shows the perspective view of a second cartridge in the process of being deployed onto the well abandonment frame,

Figure 22 shows the second stage cartridge in place in preparation for further well

Fipre 23 shows the perspective view of the well abandonment frame where the piles arc being removed.

Figure 24 shows the process of the retrieval of the abandonment frame following the completion of the second stage of abandonment operations.

Figure 25 shows in perspective view? the removal of the combination of the wrell abandonment frame and the second stage cartridge,

Figure 26 shows the well head rpadv for removal.

Figure 2? shows the resulting cleared seabed without any traces of the well bead following its removal.

Detailed Description of fee Figures la order to arrive at the configuration shown in Figure 1 a number of existing well head protecti ve structures may be removed via a combination of divers and remote operated vehicles (so called ROVs). Protective structures may for example take the form of a framework which is sufficiently remote from the well head itself in order not to constitute; a load risk. Well head 1 comprises a well head tree 2 ft® which four guide posts such as guide post 3 extend. Generally, the pride posts 3 are configured to withstand a certain degree of load compared to the central portion 4 of the well head which is relatively weak and susceptible to feitoe in well heads which have been abandoned for over thirty years. In this embodiment, the well head extends from a seabed 5 and is surrounded by pipes such as pipe 6. These pipes may be abandoned conductors or other forms of pipe work.

Figure f shows a vessel 7 with a crane or articulated arm 8 for lowering on its cable 9 a guide Same 10. An ROV ora combination of divers may be deployed to assist in the positioning of the guide frame onto the various guide posts of the well head.

Figure 3 shows in further detail the components of the guide frame 10. Guide frame 10 comprises a ring 12 defining the outermost periphery of the guide frame. A rectangular frame work 13 links together a number of sleeves such as sleeve 14 Sleeves 14 incorporate at their lower extremity a funnel shaped portion 15 which facilities the enppment of the sleeve 14 onto a corresponding guide post 3. The rectangular framework 13 is joined to the rim or ring 12 via radially extending struts such as strut 16.

Optionally one of the sleeves 14 incorporates an extension rod 17 extending upwards from the sleeve 14. Other embodiments do not necessarily comprise extension rod 17.

Figure 4 shows guide frair e fully engaged on toe guide posts 3 of the well head. Identical numerical references have been used in Figure 4 for clarity. figure 5 describes in detail the positioning of the well abandonment frame generally referenced 18 over the combined well head 1 and its corresponding guide frame 1:0. As shown M. slpre 5, fame 18 comprises a plurality of upwardly extending legs such as leg 19. The configuration of the frame is in the present embodiment a generally rectangular form with a leg at each comer of the rectangle. Other configurations may be envisaged dependent upon the layout of the obstacles on the corresponding seabed where the frame is to be deployed. Each leg incorporates an upper funnel 20 for facilitating the insertion of an appropriately sized pile (not shown in the figure). Each leg may comprise a tunnel extending the length of the leg in order to accommodate the pile. In addition, a plurality of lochs 21. are provided preferably at an upper portion of the leg. These may be configured to tighten radially onto the pile if one is located within the tunnel. In this configuration, four individual locking mechanisms are provided about the perimeter of the leg. A second set of four looking mechanisms such as mechanism 21 is provided underneath the first set in order to ensure that there is no vertical movement between the leg and a pile once it is located in the leg. Preferably, the locking mechanism may be a hydraulic locking mechanism which may be advantageously remotely controlled.

Alternatively, die locking mechanism may be a mechanical mechanism which may he either remotely controlled or activated directly by an operator using a remotely operated vehicle or requiring tie services of a diver. A mud mat 22 is provided for each one of die legs. The mud mat may incorporate a central aperture 23 for the insertion of the leg and to facilitate die relative displacement of the mud mat. The mud mat may be driven or displaced by one or more rams or hydraulic actuators 24. In the embodiment shown there are two diametrically oppositely located hydraulic rams 24 and 25. The lower extremity of the hydraulic ram may he joined to the mud mat via a triangular mount 26 and a transverse bar 27 extending the length! of the rectangular mud mat A pivot point may be provided between the triangular mount 26 and the extremity of the displaceable ram 24. This would allow the mat not only to he displaced in foe vertical direction but also accommodate a certain degree of incline should one he required dependent upon fee surface of the seabed. In § preferred embodiment, each one of the legs is configured in this form and may be remotely controlled for optimum positioning and levelling relative to the seabed and the wellhead on which an abandonment operation is tp be carried out. Between the various legs a framework of transverse and vertical struts are provided with a primary function to support an arrangement of several preferably concentric rings in particular rings 28,29 and 30.

An upper set. of supporting sings is formed first of all by cross beams such as beam 31 which extend between the legs of the frame. Thereafter, a number of diagonal beams such as beam 32 extend fern the respective legs towards the upper ring 28. At the middle section of the dross beams 31 further struts extend from the cross beam to the ring such as beam 33. At that jnnetion beams also extend between the upper eross beam 31 and a lower cross beam 34 in ftp form of vertically extending beam 35. Further beams extend in substantially the downwards direction between the various rings 28. 29 and 30 in order to form overall the impression of an hourglass formation, These are for example referenced 36» 37 and 38.

The relative size of the guide frame 10 and the respective rings 30 and 29 allow ibr the positioning of tfmguide Same within the rings in a substantially concentric manner whilst allowing a degree of movement of the frame as it is lowered onto the seabed without causing damage to the well head iiseli

As can be seen in the Figure 6 the frame may be positioned with accuracy and concentrically rel ative to the well head tree. As shown in Figure 8 once the frame is in position the mud mats may be lowered and the piles when necessary may be driven through the tunnels provided in each one of the corresponding legs. As can be seen in Figure l the hydraulic jacks may be extended in order to achieve the desired level for each one of the legs.

Figure 9 shows the piles driven into the seabed at a greater depth than in Figup? 8. The depth to which the piles are driven into the seabed will depend upon the nature of the seabed and the sped tic requirements for the frame itself.

With the abandonment support frame in position the first stage blow out prevention (BOP) support crown section may be installed, litis support crown section may take the form of a first cartridge 39 as shown in Figure 11. The first stage cartridge 39 is configured to interface with ring 28 of the support frame. Cartridge 39 may be lowered down onto the abandonment frame via appropriate cabling and with the controlled use of remotely operated vehicles (ROVs). Cartridge 39 lias a primary interfacing ring 40 with a plurality of jacks 41 which are configured to dampen substantially in the vertical direction. These act as remotely controlled dampers in preferred embodiments. The jacks are configured to allow a four-way dampening effect to minimise any load transfer during install ation of the cartri dge, hi addition, the cartridge incorporates a number of downwardly extending guide rods such as guide rod 42 which incorporate a tapered lower surface to facilitate the centralisation of the cartridge as these will first come into contact with ring 28 of the frame. Above ring 40, there is provided a boxlike section 43 within Which workover equipment is earned. A number of bowed shaped portions 44 extend across the upper portion of the boxlike section.

Once the cartridge 39 is in position there are a number of locking mechanisms which may be deployed to secure the cartridge into place. Figure 12 shows in greater detail how the cartridge is guided into contact With the upper ring ||i As c|| he seen the vertically extending rods such as rods 42 arc joined together by linkages such as linkage 45. Workover equipment4| incorporates two downwardly extending members 47 and 48 Which may engage corresponding port ions of the well head tree 49 and 50.

Figure 13 shows the interconnection of the cartridge with the frame in greater detail. Numerical references have been deliberately omitted for clarity.

As previo usly mentioned there may be several types of locking mechanisms to secure the cartridge onto the frame. Figure 14 shows a first locking mechanism generally referenced 51. The locking xncchabism is attached to the cartridge 39 and is designed to secure onto the ring 28. The locking mechanism 51 incorporates two jaws 52 and 53 which Ihsoscpoftate a pivot-point such as pivot point 54 the front lower portion of jaw 52 has a radius 55 corresponding substantially to half of the circumference of ring 28. A slider 56 is provided and attached to the cartridge 39 which is displaceable in the vertical direction, provided sufficient pressure is applied on lower legs 57 and 58. Tire upper portion 59 joins iulage arms 60 arid 61 which act eccentrically relative to the pivot point 54 in order to eanse the jaws to dose when these are lifted due to the pressure applied on the lower portions 57 and 58 thereby damping the cartridge onto the ring.

An alternative fbnn of looking mechanism is presented in figure 15 Wfae the cartridge 39 is shown in a repos corresponding to the damper and where an arm 62 extends between a portion of the cartridge and a pivot point 63 located in a lata# protrusion preferably to one side of the ring 28, Appropriate mechanical fixing means may he provided in order to prevent the vertical displacement o f the cartridge relati ve to the frame.

As shown in Figure 16 a workover section of known kind may be deployed on the upper portion of the cartridge. Upon completion of necessary workover operations the well may now be plugged, and the tree of the blowout prevention cartridge may be retrieved as the tree may be safely disconnected ifom the well head, The first cartridge may be .retrieved along with the now loose tree as shown in Figure 17, This first stage leaves the well head exposed in preparation for the second stage blowout prevention operation which employs a further kind of cartridge as shown in Figures 19 to 25,

Figure 19 shows the installation process for the second cartridge 65. Cartridge 65 as shown in Figure 20 incorporates a well head extension connector 66 secured onto the central axis of the cartridge’s ring 67, A number of radially extending junction members 68 are provided towards a central support 69. As in the previous embodiment, cartridge ring 67 relies on a number of vertically extending guide rods 70 whose lower extremity; are at an angle in order to locate and centralise on the frame. In addition, the cartridge employs a plurality of jacks or dampers 71 which as before allow the engagement of the interfacing rings to be controlled if necessary through remote control means in order to manage the loading ox the frame with caution. On a similar basis as the previously deployed locking mechanisms the second cartridge will also envisage their deployment in order i> lock the interfacing rings together for the duration of the operation. Once all sections of the abandonment frame have been installed stage two operations may be carried out. In particular a five stack subsea blowout prevention device may be landed off onto the second cartridge as shown in Figure 22 and thereafter facilitate well abandonment operations which may be completed from a rig. Once abandonment operations have been completed, the well head may be cut beneath the surface and retrieved as a complete assembly leaving the seabed entirely dear as shown in Figure 27. Advantageously, the frame and the second cartridge maybe removed together in order to simplify the removal process. Any remaining debris and pipework that may have been disposed in the vicinity of the well head may also now be removed in order to achieve an entirely dear seabed.

Claims (22)

1. A well abandonment frame for fitting over a well head to facilitate one or more abandonment operations comprising a plurality of upwardly extending load bearing legs and a plurality of junction members joining said legs to forms said frame; said junction members presenting an aperture through which said abandonment operations are carried out; said aperture being defined by a rim for engagement with one or a succession of cartridges which are secured to facilitate one or a plurality of abandonment operations,

2. A well abandonment frame according to claim 1, wherein said rim is circular.

3. A well abandonment, frame according to either claim 1 or claim 2, wherein said frame incorporates a plurality of concentric rims,

4. A well abandonment frame according to claim 3, wherein said plurality of concentric rims incorporate a lower rim, an intermediate rim and an upper rim; the intermediate rim having a diameter which is lower than both the diameter of the upper and low® rims.

5. A well abandonment feme according to any of the preceding claims, wherein said legs incorporate means for adjusting the length of said legs.

0, A well abandonment frame according to claim 5, wherein said legs incorporate a mud matt and means for vertically displacing said mud matt.

7. A well abandonment frame according to any of Hie preceding claims, wherein one or more of said legs incorporates a longitudinal tunnel and accommodate a pile which may be driven into the bed on which the frame is mounted.

8, A well abandonment frame according to claim 7, wherein the upper aperture of said longitudinal tunnel incorporates a ftianeL

9. A well abando^^^^e::^ecofding to claim 7 or claim 8, Aomin said legs incorporate a plurality of locks for locking said l|g onto said pile.

10. A well abandonment frame substantially as hereinbefore described and/iliusirated n any appropriate combination of tbs accompanying text and/or figures.

11. A cartridge tor securing to a well abandonment frame according to any of claims 1 to 10, comprising a rim for securing to the upper rim of a frame according to claim 4, and a plurality of downwardly extending guide rods tor centralising said rim onto said upper rim.

12. A cartridge according to claim 11, wherein said rim. incorporates a plurality of dampers for engaging said upper rim.

13. A cartridgeaccording to claim li, wherein said dampers are adjustable in height by remote control. K A cartridge according to any of claims 11 to claim 13, further comprising a locking mechanism.

15. A cartridge according to any of claims 11 to claim 14, further comprising an arm Hr locki ng said cartridge onto said upper rim.

16. A cartridge according to any1 of claims 11W claim 15, further comprising a locking jaw whicfrelamps onto said upper rim.

17, A cartridge according to any of claims 11 to claim 16. Hither comprising means for carrying out a workover operation.

18, A cariridge aceniriing to^any of claim 11 to claim 17, further comprising a wellhead extension. Ϊ9. A cartridge substantially as hereinbefore described and/or illustrated in any appropriate combination of the accompanying text and/or figures.

20. A well abandonment system comprising a frame according to any of claims i to 10 and a cartridge according to any of claims 11 to 19. A system according to claim 20, wherein said well head incorporates guide posts and said system further comprises a guide framefor securing to the well head’s guide posts.

22. A method of carrying out abandonment operations on a well head annprising the steps of providing a frame according to any of claims 1 to 10, positioning said; frame about said well head, and carrying out one or mol® operations by employing one or a succession of cartridges according to any one of claims 111©: 19.

23. A method according to claim 22, wherein the well head incorporates guide posts and the method further comprises the step pf seeming a jguide frape to said guide posts.

24. A method according to either claim 22 or claim 23, wherein said frame incorporates mud mails and said method further comprises the step of remotely controlling the position of said mud matts.

25. A method according to any of claims 22 to claim 24, further comprising tie steps of locking one or a succession of said cartridges to said frame.

26. A method of carrying out abandonment operations on a well head substantially as hereinbefore described and/or illustrated in any appropri ate combination of the accompanying text and/or figures.