EP2739790B1 - Cutting of an off shore pile - Google Patents

Description

The invention relates to a method and a device for separating upright, anchored with its lower end in the ground pipes of greater length and larger diameter, typically a length approximately between 30 and 200 m and a diameter of about 1800 mm, in particular anchoring pipes of an offshore Oil drilling or production platform. The wall thickness is typically 50 to 100 mm.

Depending on the nature of the seabed, on which offshore oil drilling or production platforms are located, the steel anchoring pipes of these platforms are only embedded in the seabed, for example, rammed and held by the friction in the seabed. If this is not sufficient, the alternative is to introduce into the recessed foot of the anchoring pipes underwater concrete or the like, which may escape partially from the lower end of the tube in the surrounding seabed and after curing forms an artificially anchored in the seabed foundation its anchoring effect is added to the effect of the weight of the concrete, which fills the lower part of the respective tube up to a certain height. When dismantling platforms, regulations often require that the anchoring pipes be separated a bit below the seabed.

Methods and apparatus for separating upright, with its lower end anchored in the ground pipes of greater length and larger diameter are already known. In particular, the DE 196 20 756 A1 Such a method and apparatus.

From the DE 42 10 895 A1 For example, there is known a cutting head for cutting a pipe having a cutting nozzle to which a pressurized abrasive is supplied via a conduit, the cutting nozzle being rotatable about the central axis of the cutting head and the cutting head having a clamping device for clamping against the inner wall of the pipe. Fig. 1b shows in an embodiment for narrow pipes an inclined cutting nozzle.

A disadvantage of known methods and devices is that under the extremely harsh environmental conditions (often under high pressure seawater, mixed with drilled concrete or seabed) partially undesirably reliable function or / and a lot of effort is required to support the severed pipe or to intercept.

The invention has set itself the task of providing a method and an apparatus which is improved in terms of these disadvantages. This object is achieved by the method set forth in claim 1 and the device reproduced in claim 4.

In the inventive method for separating upright, anchored with its lower end in the ground pipes of greater length and larger diameter, in particular anchoring pipes an offshore oil drilling platform is lowered by the upper end of the pipe to be separated a cutting unit into the pipe to a separation zone , The cutting unit acts progressively against the pipe over the circumference. The separation process takes place by means of a water jet emerging from at least one water jet nozzle. The pipe wall is cut to create two complementary conical cut surfaces by a cut with at least almost constant cutting width, which extends obliquely through the pipe wall. To effect the oblique section of the water jet is the at least one Water jet nozzle at an angle α, which may for example be between 5 ° and 60 °, aligned to the plane perpendicular to the tube axis A plane E.

Based on the (wandering) cutting axis, this angle α preferably remains constant. The term "water jet nozzle" are in the following, unless otherwise specified in the context, also referred to several water jet nozzles.

If above or below "upright pipes" is mentioned, this does not necessarily mean a vertical orientation of the pipes. Also from the vertical inclined pipes that extend from the bottom upwards are detected.

The water jet cutting is reliable even under harsh environmental conditions, especially if, as preferred, the pipe wall is cut in one operation, since then only a very low feed is needed, and avoid existing rocks, without causing damage.

The separation zone is preferably below the seabed.

The angle α is preferably 30 °.

The weight of the tube and any connected components is not intercepted by additional devices in the separation process. It has been shown that this can be dispensed with because of the self-centering, conically complementary cut surfaces. As a result, a significant cost savings can be achieved. The pipe is even after the separation process to a limited extent further resilient. Because the self-centering minimizes the risk that a lateral offset of the tubes in the separation zone occurs and thereby the bearing surfaces are reduced to such an extent that they no longer withstand the forces, also due to any corrosion damage.

In one embodiment, a plurality of water jet nozzles are evenly distributed over the circumference of the cutting unit. Particularly preferably, two water jet nozzles are provided, which are particularly preferably arranged diametrically. As a result, the separation process is faster compared to just a single water jet, with justifiable overhead.

Preferably, after a rotation through 360 ° divided by the number of water jet nozzles, raising and lowering of the cutting unit takes place while the water jet is still switched on, so that cuts are made in the direction of the pipe axis. In the case of only a single water jet nozzle, lifting and lowering are thus preferably carried out after a 360 ° rotation, with two diametric water jet nozzles preferably after a rotation of 180 °. The vertical cuts always run at the point where two cuts meet. The then resulting cutting scheme is able to compensate for variations in height during the cutting process, so even if a secure separation of the tube to cause, if the height of the cutting unit varies relative to the pipe during the cutting process.

The resulting in height variations, optionally one or more jumps having cut surface is also referred to in the context of this document as a conical cut surface.

In the event that material is present in the pipe in the zone in which it is to be separated, such as seabed or concrete, with which the pipe may be poured out for better anchoring in the ground, this material is preferred when lowering the cutting unit from above Drilled through the pipe and indeed to below the separation zone.

The cutting unit is preferably firmly connected to the drill string, more preferably flanged.

To accelerate the separation process, the inner wall of the tube is preferably cleaned in the region of the separation zone. So it is concrete or seabed, which can still adhere to the pipe walls after any drilling, away. This is preferably done by roller drill bits. These can, if they are in the area of the separation zone, be switchable or constantly, so be during the entire drilling or lowering operation in use.

• Aufbohren des in dem Rohr befindlichen Materials, wie Meeresboden oder Beton, bis unter die Trennzone,
• Anheben des Bohrstrangs um etwa 0,5 m und Höhen-Fixierung des Bohrstrangs,
• Abschalten des Haupthydraulikantriebs des Bohrstrangs und Zuschalten eines Hilfshydraulikantriebs,
• Ausfahren und Positionieren der mindestens einen Wasserstrahldüse,
• Inbetriebsetzen des Wasserstrahls.

The following method steps are preferably provided:

• Drilling of the material in the pipe, such as seabed or concrete, to below the separation zone,
• Lifting the drill string by about 0.5 m and fixing the height of the drill string,
• Disconnecting the main hydraulic drive of the drill string and connecting an auxiliary hydraulic drive,
• Extension and positioning of the at least one water jet nozzle,
• Start up the water jet.

The following further method steps may be provided:

After boring, it is possible to connect water pipes and any electrical lines of the drill string, preferably via quick couplings. These can therefore still be unconnected during the lowering or drilling process. After commissioning of the water jet can be maintained until a sensor, preferably a hydrophone, detects the passage of the water jet through the pipe wall. Then the auxiliary hydraulic drive can be put into operation. The feed rate, ie the rotational speed of the auxiliary hydraulic drive, can be increased until the sensor detects an incomplete section and then reduces it until a complete passage of the water jet through the pipe wall is detected again. Thereupon, the cutting process can be aborted and completely carried out elsewhere (slightly higher or lower) with the thus obtained and optimized parameters. All parameters can be saved here.

Preferably, abrasive particles are added to the water. Thus, the separation process is a so-called "abrasive jetting" process.

Water jet nozzles used for this process are also referred to as "water abrasive jet cutting nozzles" or "WAS cutting nozzles" for short.

Preferably, an air jacket of a plurality of air nozzles is generated around the water jet. This achieves better performance.

In a particularly preferred embodiment of the method according to the invention loose solids are transported out of the interior of the tube during the separation process. Surprisingly, it has been found that this accelerates the separation process and improves the quality of the conical cut surfaces. An explanation for this could be that despite the relatively small cutting width, which is effected during the separation process, the separation process negatively affecting amounts of loose solids, such as sand between the cut surfaces in the pipe interior passes.

The outward transport is preferably carried out by using the so-called air lifting method known per se. In this, air is injected into the drill string interior in a hollow drill string which is at least substantially filled with water at a location below the water surface, preferably in the vicinity of the location in which the transport is to take place. The drill string has a suction opening below the injection point. Due to the change in density of the water column caused by the injected air, a flow is produced upwards in the interior of the drill string, which sucks and removes water and loose solids in the vicinity of the suction opening into the interior of the drill string.

If the method according to the invention also includes the step of boring the pipe filled, for example, with concrete, then, using the same air lifting method, dissolved material, for example concrete particles, can also be conveyed out of the pipe interior during the drilling process.

In its device-side aspect, the object is achieved by a device for separating upright, anchored with its lower end in the ground pipes of greater length and larger diameter, in particular anchoring pipes an offshore oil drilling or production platform, the device comprising a cutting unit which is lowered through the upper end of the pipe to be separated in this up to a separation zone. The cutting unit comes in this preferably axially narrow separation zone on the inner circumference of the tube in the circumferential direction progressively to the effect and cuts through the tube. To effect the separation process at least one water jet nozzle is provided. Positioning means are provided which position the water jet nozzle relative to the pipe wall in such a way that the water jet issuing from the water jet nozzle impinges on the pipe wall at an angle α to the plane perpendicular to the pipe axis such that two complementary conical cut surfaces result when the separation has taken place. In this way, in the separation zone after separation, the pipes lie flat against one another at these cut surfaces. They center themselves, so that the pipe can continue to absorb forces, in particular compressive forces to a limited extent. A support or a catching of the separated pipe can be dispensed with.

Preferably, the angle α is 5 ° to 60 °, more preferably about 30 °. It has been found that in this way a sufficient self-centering, given tolerable tensile or compressive forces in the circumferential direction in the pipe wall at the cut surfaces is given and increases the cutting length only to a tolerable extent. By tensile or compressive forces in the circumferential direction, the forces are meant that arise due to the conical shape of the cut surfaces and spread a pipe end and want to squeeze the adjacent pipe.

More preferably, two water jet nozzles are provided.

Under the cutting unit a drill head is preferably arranged, by means of which in the lower region of the tube befindliches material, such as seabed or concrete or the like, with which the tube may be poured for better anchoring, on the inner cross section of the tube is drilled to a depth, so that the cutting unit can be brought to the intended separation zone for use.

The drill head is preferably rotatably driven. The cutting unit is preferably fixedly connected to the drill head or to the drill pipe.

Preferably, additional auger bits are provided to clean the inner wall of concrete or seabed debris or the like. These are preferably radially biased. They can be constantly engaged or switchable, so that only in the area of the separation zone is used.

Preferably, an auxiliary hydraulic drive is provided in addition to the main hydraulic drive of the drill string, which can be brought into use during the separation process and provides only a small torque and rotates extremely slowly and is characterized by a particularly uniform speed. The speed may be, for example, one revolution per two hours. As a result, the required uniform and slow feed for the water jet nozzles is achieved, thus achieving a secure separation.

The positioning means preferably comprise a guide carriage with guide rollers which can be brought into contact with the tube inner wall. The water jet nozzle is preferably fixed and connected at a selected angle to the guide carriage, so that the water jet is automatically aligned in the correct constant angle to the pipe wall when the carriage abuts the pipe wall, as well as the constant nozzle spacing is ensured to the cutting surface.

Preferably, extension means are provided which comprise a pneumatic cylinder and a spring. The water jet nozzle is thus preferably with the carriage and further preferably by a pneumatic cylinder extendable. Thus, there is provided a retracted position of water jet nozzle with carriage, which is preferably taken during the lowering and recovery of the cutting unit in the pipe and an extended position when the cutting unit comes into use.

To the water jet nozzle are preferably provided a plurality of air nozzles. By blowing out air during the cutting process, the water jet of the Separated ambient water and so avoided that the water jet is braked by ambient water and so the efficiency of the device is reduced.

As stated, two water jet nozzles may be diametrically located, in the same plane. Each nozzle needs to cut only half the circumference. As a result, the cutting time is almost halved compared to only a single water jet nozzle. In an equally conceivable larger number of water jet nozzles, which are distributed uniformly over the circumference, their number corresponding.

In one embodiment, two water jet nozzles are arranged behind one another in the same plane to a pair of water jet nozzles. Each nozzle must cut the full circumference and the cutting time is twice as long as two diametrical water jet nozzles. The advantage here is that a higher level of security is achieved that the full cross-section is completely severed. Because one of the two water jet nozzles cuts through with at least almost certainty, even with any jumps (ie irregularities) in the feed.

It is conceivable that a plurality of diametrical or uniformly distributed over the circumference water jet nozzle pairs are provided. In the embodiment of the method according to the invention in which, after a rotation through 360 ° divided by the number of water jet nozzles lifting and lowering of the cutting unit is still connected with the water jet, the number of water jet nozzles means the number of water jet nozzle pairs.

Preferably, at least one sensor is provided, which detects the passage of the water jet through the pipe wall, preferably a hydrophone. In this way, a secure complete cutting of the tube can be achieved with the shortest possible cutting time.

Very particular preference is given to an embodiment of the device according to the invention in which means are provided, with which during the separation process loose solids from the inside of the tube are transported out. "Loose solids" is to be understood in particular as seabed, which passes into the interior of the pipe during the separation process between the cut surfaces and can hinder the separation process there. If a drill head is arranged below the cutting unit, by means of which material located in the lower region of the pipe can be drilled out, then it is preferably the same means with which the dissolved material can be transported out during this drilling operation.

The means are preferably designed such that the outward transport of the loose solids takes place with the aid of the air lifting method. For this purpose, a suction opening communicating with the inner volume of the drill string and preferably above the cutting unit on the drill string, an air injection opening communicating with the inner wall thereof are provided on the drill string on which the cutting unit is arranged. To the air injection port can be connected to the drill string fixed air line, which is connected to a arranged outside the pipe compressor.

Fig. 1

perspektivisch eine Stützkonstruktion mit davon abgehobener Förderplattform;

Fig. 2

schematisch eine Seitenansicht einer Stützkonstruktion;

Fig. 3

eine schematische Seitenansicht eines Bohrvorgangs im Lufthebeverfahren;

Fig. 4

eine Seitenansicht eines erfindungsgemäßen Bohrkopfes mit fest darüber angeordnetem Schneideaggregat in eingefahrener Position;

Fig. 5

eine Ansicht wie in Fig. 4 in größerem Ausschnitt;

Fig. 6

eine Ansicht wie in Fig. 4 mit Schneideaggregat in ausgefahrener Position;

Fig. 7

eine Ansicht wie in Fig. 6 mit Blick in Richtung der Rohrachse;

Fig. 8

eine Detailansicht aus Fig. 6;

Fig. 8a

eine Detailansicht von Fig. 4

Fig. 9

eine Detailansicht aus Fig. 6 mit Schnittschema;

Fig. 10

eine weitere Detailansicht aus Fig. 6 mit geändertem Blickwinkel;

Fig. 11

eine rein schematische Darstellung des erfindungsgemäßen Verfahrens und der erfindungsgemäßen Vorrichtung;

Fig. 12

ein Stützbein 2 mit Verankerungsrohren 2a;

Fig. 13

ein weiteres Ausführungsbeispiel eines Schneideaggregatzwischenstücks;

Fig. 14

eine schematische Seitenansicht einer erfindungsgemäßen Vorrichtung während des Abtrennvorganges;

Fig. 15

die Einzelheit X in Fig. 14 in einer vergrößerten Darstellung.

The invention will now be explained with reference to shown in the drawings embodiments. Show it:

Fig. 1

in perspective, a support structure with lifted off conveying platform;

Fig. 2

schematically a side view of a support structure;

Fig. 3

a schematic side view of a drilling operation in Lufthebeverfahren;

Fig. 4

a side view of a drill head according to the invention with fixedly arranged above cutting unit in the retracted position;

Fig. 5

a view like in Fig. 4 in a larger section;

Fig. 6

a view like in Fig. 4 with cutting unit in extended position;

Fig. 7

a view like in Fig. 6 looking in the direction of the pipe axis;

Fig. 8

a detailed view Fig. 6 ;

Fig. 8a

a detailed view of Fig. 4

Fig. 9

a detailed view Fig. 6 with cutting scheme;

Fig. 10

another detail view Fig. 6 with a different perspective;

Fig. 11

a purely schematic representation of the method and apparatus of the invention;

Fig. 12

a support leg 2 with anchoring tubes 2a;

Fig. 13

another embodiment of a cutting unit intermediate piece;

Fig. 14

a schematic side view of a device according to the invention during the separation process;

Fig. 15

the detail X in Fig. 14 in an enlarged view.

In the Fig. 1 For example, an example of an oil drilling or production platform 100, already separated into its main components, is shown, which includes an actual platform 20 which, when assembled, is supported on a support structure generally designated 21. The entire equipment normally arranged on the platform 20, such as boring device, accommodation, etc., has already been dismantled and is no longer reproduced in the drawing. For mounting and dismounting of the oil well or conveyor plate molds 100 and / or the support structures 21 are crane ships 46 used, the cranes 19 have the lifting height above the sea level can be 100 m and more. In the illustrated phase, the actual platform 20 depends on the release of the support structure 21 already on the cranes 19. From the support structure 21 is in Fig. 1 only above the sea level 23 ( Fig. 2 ) part, which can be 30 m to 40 m high. The support structure 21 is formed as a tower or bock-like framework with support legs 2 and truss-like cross braces and anchored by means of their reaching down into the water (indicated by dash-dotted lines) anchoring pipes 2a under the water surface in the seabed. For this purpose, the tubes 1 are also filled with concrete in their lower area. The water is usually between 30 and 200 m deep and it can be embedded by a comparable distance in the seabed, each anchoring tube 2a, z. B. be rammed. The anchoring pipes 2a are therefore very long. They consist of large pipes 1 of 1800 mm in particular diameter and considerable wall thickness of 80 mm in particular.

Fig. 2 illustrates the disassembly situation of a support structure 21, the constructive something of Fig. 1 differs. The upper parts 26 of the support legs 2 are cut off at the freely accessible Abtrennstelle 22 and still belong to the actual platform 20, according to Fig. 1 lifted from the cranes. The support structure 21 protrudes above the sea level 23 and extends down a distance corresponding to the water depth to the seabed 8. The anchoring pipes 2a extend deep into the seabed and can be anchored at its lower ends by pressed underwater concrete or the like fundamentally in the seabed 8 be. In the task of an oil drilling or conveying platform 100 is often required that the anchoring pipes 2a are separated at a distance 24 of a few meters below the seabed 8 separation points or separation zones 4 of their reaching deep into the seabed 8 lower ends. The separation zones 4 are difficult to reach from the outside.

Fig. 3 shows general information regarding the so-called air lifting principle. There is provided an air lifting pipe or drill string 29, at the lower end of a drill head 36 is arranged. This can be, for example, a Rock drill head or rock drill bit trade. In the drill string 29, a compressed air line 27 is guided at the upper end via an air lift-flushing head 31. The compressed air is guided down the drill string to the compressed air inlet valve 30. There it flows through a suction opening 48 into the interior of the drill string 29 and creates a buoyancy, is raised by the drill head 36 dissolved seabed through the interior of the drill string. This overburden or excavation 34 passes through an outlet hose 33 in a mine pit 35. At the upper end of the drill string, a power rotary head or a rotary drive 32 is provided. Around the drill string around a standpipe 28 is arranged.

Since the separation zone 4 is difficult to reach from the outside, the tube 1 is severed from the inside. In the embodiment shown in the figures is the method and the device that is used when the pipe 1 is filled to above the separation zone 4 with concrete 16 or soil or the like.

Fig. 4 shows the drill string 37, which is designed as Lufthebbohr tube or strand 29. At its lower end a rock drill bit or rock drill bit 36 is arranged. Between the drill head 36 and the drill string 37, a cutting unit adapter or cutting unit adapter 47 is arranged. This is in each case connected by means of a flange with the drill head and with the drill string. The cutter assembly adapter 47 may be attachable to a conventional drill pipe 37 and a conventional drill bit. The cutting unit adapter or the cutting unit adapter 47 comprises the cutting unit 3.

Fig. 5 shows a larger area of the drill string 37. In the upper part of Fig. 5 a stabilizer 38 can be seen, which is supported in the tube 1 and in which the drill pipe 37 is rotatably mounted. It can be provided several drill collars.

Fig. 6 shows the cutting unit 3 in action. The cutting unit 3 comprises two water jet nozzles 5, 5 '. The water jet nozzles are progressing in a plane E substantially perpendicular to the tube axis A in the circumferential direction of the tube 1 displaced. The two water jet nozzles are diametrically opposed. It is also possible that they are arranged directly next to each other to ensure a safe cut and to increase the redundancy (not shown in the figures). In particular Fig. 8 can be seen, 5 more air nozzles 14 are arranged around each water jet nozzle. The water jet nozzles 5, 5 'are respectively positioned by positioning means 9a, which comprise a guide carriage 11, 11' with guide rollers 12, 12 '. Each water jet nozzle 5, 5 'is thus arranged on a carriage 11, 11', each having four guide rollers 12, 12 '. In the extended position of the water jet nozzles 5, 5 'are the guide rollers 12, 12' on the pipe inner wall. The water jet nozzles 5, 5 'are each firmly mounted on the guide carriage 11, 11' in such a way that the water jet 15 does not strike the tube wall 6 parallel to the plane E, which runs perpendicular to the tube axis A. Especially Fig. 8 shows that the water jet nozzle 5 and the water jet emerging from it instead assumes an angle α of 30 ° to this plane E. The same applies to the other water jet nozzle 5 '. The cutting width B is small and almost constant. In this way, when the guide carriages 11, 11 'have completely traveled the inner circumference of the tube 1 and the water jets have completely severed the tube, complementary, conical cut surfaces 7c, 7d are created. The tube above the separation zone 4 thus supports itself in a self-centering manner on the tube remaining below the separation zone 4. It does not necessarily have to be supported or intercepted.

The water exits the water jet nozzles 5, 5 'at a very high speed.

Fig. 9 shows the sectional diagram 7a of the water jets. After both water jet nozzles 5, 5 'have passed through the complete inner circumference of the tube 1 together, so after a 180 ° rotation of the cutting unit 3, the cutting unit 3 is raised and lowered slightly. From this results in the direction of the tube axis extending sections 7e (in Fig. 9 recognizable only on one side) which compensates a height variation of the cutting unit 3 during the cutting process, which can last for several hours. Lifting and lowering the cutting unit with the water jet switched on takes place to a degree, so that the tube 1 is severed sure of the expected height variations.

The water jet nozzles 5, 5 'and the positioning means 9a are extended by means of extending means 9 from a retracted position to an extended position. The extension means 9 comprise a substantially straight pivot arm 40, and a pneumatic cylinder 10. The pivot arm 40 has at one end rotatably mounted on the carriage 11 or 11 'on. At its opposite end it is rotatably mounted on the other cutting unit 3. In a central region of the pivot lever, which is arranged closer to the cutting unit side bearing than at its other end, the free end of the piston rod of the pneumatic cylinder 10 engages the pivot arm 40 via a rotatable connection. The pneumatic cylinder 10 itself is also rotatably or pivotally attached to the cutting unit 3.

Like for example Fig. 6 3, three additional roller bits 18, 18 ', 18 "are arranged on the drill head 36. These clean the inner wall of the tube 1 in the region of the separation zone 4 of concrete 16 or seabed 8 remaining thereon. The additional roller drill bits 18, 18', 18 are each biased by a pneumatic cylinder 18a ( Fig. 11 ). The cutting unit 3 is thus associated with an annular region in the separation zone to the metal of the tube 1 of adhering material cleaning device, which includes the additional roller drill bits 18, 18 ', 18 ".

Above and below the water jet nozzles 5, 5 'and their extension means 9 and positioning means 9a fenders 39 are provided. These are rigid and protect the water jet nozzles and the extension means and positioning means in the retracted position of the water jet nozzles 5, 5 '.

When the pneumatic cylinder 10 in the retracted position of the water jet nozzles 5, 5 'is subjected to air pressure and extends, it pivots the pivot arm 40 from a voltage applied to the periphery of the cutting unit 3 Position in a spread apart from this extent extended position in which the carriage 11 abuts the pipe inner wall.

Fig. 11 illustrates the device of the invention and the inventive method in a highly schematic. The elements are sometimes not drawn in their "correct" position. It shows the drill pipe 37, at the lower end of the drill head 36 is arranged. To the right of this is shown an additional roller drill bit 18 which is biased by a pneumatic cylinder 18a. Left of the drill head 36, the elements of the cutting unit 3 are shown. It can be seen the extension means 9, which include the pneumatic cylinder 10 and the pivot lever 40. The carriage 11 is not shown. There is a water jet nozzle 5 visible and a jet of water 15. Different than in Fig. 11 shown, the water jet 15 only an extremely small expansion. The water jet nozzle 5 is connected by means of a water line 13 with a mixing valve 44, are mixed over the abrasive particles 43. The high-pressure water pump 41 is shown, with the further water line 42. On the other side of the drill string 37, a compressor 45 can be seen. The compressed air line leads shown on the right side of the drill string via the Lufthebespülkopf 31 to the compressed air inlet valve 30, via which the compressed air for the air lifting method is blown into the drill pipe 37. Shown on the other side of the drill string 37, the air pressure line extends to the cutting unit 3. There it divides again in a line to the pneumatic cylinder and another line to the air nozzles 14th

Fig. 12 shows an example of a support leg 2 with anchoring pipes 2a to be separated. The separation zone 4 is 6m below the seabed 8 and the water depth is 140m. The anchoring pipes 2a are filled with concrete and loaded. The anchoring tubes 2a and the support legs are inclined at an angle of about 9.5 °. The seabed consists of compact sand with layers of different composition (sand and organic sediments).

The method according to the invention can be carried out under harsh conditions such as strong wind, high waves and low temperatures. limiting Factor is the dynamic support safety of the support leg 2 with severed anchoring pipes 2a in harsh weather conditions.

Fig. 13 3. The cutting unit adapter 47 in this embodiment itself comprises the additional roller bits 18, 18 ', 18 ".In addition, further roller bits 18b are provided on the drill head 36. There are two compressed air lines 27 A 27 'causes the carriage 11 to extend and directs the air jacket around the jet of water, while the other 27 "leads to the additional roller bits 18, 18' and the other roller bits 18b, 18b 'and simultaneously extends them. The functions of the two compressed air lines are independently controllable.

Another variant of the method according to the invention is based on Fig. 14 and 15 be explained.

In Fig. 14 is - schematically - a device according to the invention shown during the separation process. Previously was with the help of their arranged at the lower end of Lufthebbohrstrangs 29 drill head 36 within the tube concrete 16 drilled to below the seabed 8 and then the Lufthebbohrstrang 29 in the in Fig. 14 shown position has been raised. In this is the cutting unit 3 in a position in which the separation zone 4 is still below the seabed 8, but between the drill head and the surface O of the concrete 16 remains a free space.

Thus, in the tube 2a during the separation process still located or for example by the resulting during the separation process slots 49 loose solids, such as sea sediments 50 can not hinder the separation or even block, the air lifting is operated during this separation process by - as in Fig. 15 is shown - is injected through the compressed air line 27 and the compressed air inlet valve 30 air in the Lufthebbohrstrang 29. The air flow is symbolized by the arrows in the compressed air line 27. Because of the upward flow created thereby inside the air hoe drill string, which is to be illustrated by means of the drawn, upwardly directed arrows, sea sediment located within the anchoring pipe 2a is transported away. This is - as in Fig. 14 can be seen - by a provided above the sea level 23 inlet 51 water, in Fig. 14 symbolized by the large points, initiated, in a volume flow, so that the water level 23 'within the support tube 2a is regularly above the sea level 23.

LIST OF REFERENCE NUMBERS

100

Offshore oil drilling or production platform

1

pipe

2

support legs

2a

anchor pipes

3

cutting unit

4

separation zone

5, 5 '

water jet

6

pipe wall

7

cut

7a

sectional schematic

7b

in the direction of the tube axis running cuts

7c, 7d

complementary conical cut surfaces

8th

Seabed

9

extending means

9a

positioning means

10

pneumatic cylinder

11, 11 '

carriages

12, 12 '

guide rollers

13

water pipe

14

air nozzles

15

waterjet

16

concrete

17

free

18, 18 ', 18 "

additional roller bits

18a

pneumatic cylinder

18b

further roller bits

19

cranes

20

actual platform

21

support structure

22

freely accessible separation point

23

Sea level

23 '

water level

24

Distance of the separation zone to the seabed

25

lower ends of the tubes 1

26

upper parts of the support legs

27, 27 ', 27 "

Compressed air lines

28

standpipe

29

Air lifting pipe or strand

30

Compressed air inlet valve

31

Lufthebespülkopf

32

Power rotary head or rotary drive

33

discharge hose

34

Overburden or excavation

35

tailings pit

36

wellhead

37

drill pipe

38

stabilizers

39

fenders

40

swivel arm

41

High pressure pump (water)

42

further water pipe

43

abrasive particles

44

mixing valve

45

compressor

46

crane ship

47

Cutting unit adapter or cutting unit adapter

48

suction

49

slots

50

marine sediment

51

Intake

A

pipe axis

B

cutting width

e

Plane perpendicular to the tube axis

α

angle

O

surface

Claims (14)

1. A method for cutting off upright, bottom end ground-anchored tubes (1) of a larger length and diameter, in particular anchoring tubes (2a) of an offshore oil rig (100), within the framework of which, through the upper end of the tube (1) to be cut off, a cutting aggregate (3) is lowered into the tube (1) up to a cutting zone (4), continuously pressing against the tube (1) across the entire circumference, and the cutting process is performed using a water jet (15) escaping from at least one water jet nozzle (5, 5'), wherein the tube wall (6), in order to create two complementary conical cutting faces (7c, 7d), is cut by a cut (7) with an at least virtually constant cutting width (B), which proceeds through the tube wall (6) in an inclined manner, wherein, in order to cause the inclined cut (7), the water jet (15) of the at least one water jet nozzle is arranged at an angle (α) regarding the plane (E) located perpendicularly to the tube axis (A), wherein the weight of the tube (1) and optionally connected components is not accepted by additional devices during the cutting process.
2. The method according to claim 1, characterized in that abrasive particles are admixed to the water of the water jet.
3. The method according to claim 1 or 2, characterized in that, after a rotation by 360°, divided by the number of water jet nozzles (5, 5'), the cutting aggregate (3) is lifted and lowered with the water jet being switched on, such that this results in cuts (7b) proceeding towards the tube axis (A).
4. The method according to any of the claims 1 to 3, characterized in that, during the cutting process, loose solids are transported from inside the tube to the outside.
5. The method according to claim 4, characterized in that the transport from the tube is performed with the help of the air lift method.
6. A device for cutting off upright, bottom end ground-anchored tubes (1) of a larger length and diameter, in particular anchoring tubes (2a) of an offshore oil rig (100), using a cutting aggregate (3) that can be lowered through the upper end of the tube (1) to be cut off into the tube (1) up to a cutting zone (4), which, within this cutting zone (4), continuously presses against the internal circumference of the tube (1) in a circumferential direction and cuts off the tube (1), wherein, in order to effect the cutting process, at least one water jet nozzle (5, 5') is provided, wherein positioners (9a) are provided, positioning the water jet nozzle (5, 5') regarding the tube wall (6) such that the water jet (15) escaping from the water jet nozzle (5, 5') hits the tube wall (6) at an angle (α) regarding the plane (E) located perpendicularly to the tube axis (A), such that, after completion of the cutting process, two complementary conical cutting faces (7c, 7d) are formed, wherein the cutting aggregate (3) is connected to a drill string (37).
7. The device according to claim 6, characterized in that the angle (α) is between 5° and 60°, preferably about 30°, and that two water jet nozzles (5, 5') are provided preferably.
8. The device according to claim 6 or 7, characterized in that, below the cutting aggregate (3), a drilling head (36) is arranged, with the help of which material contained inside the tube such as the seabed or concrete (16) or the like, which may have been used to fill the tube in order to improve the anchoring, can be drilled out via the interior cross-section of the tube (1) up to a depth so that the cutting aggregate (3) can be used in the designated cutting zone (4).
9. The device according to any of the claims 6 to 8, characterized in that roller cone drill chisels (18, 18', 18") are provided cleaning the tube inner wall of concrete or the seabed or the like.
10. The device according to any of the claims 6 to 9, characterized in that, in addition to the main hydraulic drive of the drill string, an auxiliary hydraulic drive is provided that can be used during the cutting process and rotates extremely slowly and is characterized by a particularly uniform speed.
11. The device according to any of the claims 6 to 10, characterized in that the positioners (9a) comprise a guide trolley (11, 11') with guide rollers (12, 12') that can be brought into contact with the tube interior wall.
12. The device according to any of the claims 6 to 11, characterized in that several air nozzles (14) are arranged around the water jet nozzle (5, 5').
13. The device according to any of the claims 6 to 12, characterized in that means are provided, with the help of which loose solids can be transported from the interior of the tube during the cutting process.
14. The device according to claim 13, characterized in that, on the drill string, below the cutting aggregate, a suction opening communicating with the interior volume of the drill string and, preferably above the cutting aggregate, an air blow-in opening communicating with the interior volume of the drill string are provided.

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