U The invention concerns a rapid coupling system for wellheads, riser stacks, blowout preventers and diverter systems for use in well drilling, for example in exploration drilling for fluids like oil, and gasses.

The equipment used to drill oilwells is expensive to run and to maintain : it is very capital and labour intensive : heavy equip¬ ment must be lifted into place, adjusted and coupled in condi¬ tions normally requiring considerable outlays on manpower and materials . In addition, the coupling of drilling systems to the wellhead can be expensive because recognised types of coup¬ ling systems must be permanently installed at the wellhead .

When a drilling rigg is in position at a wellhead, it must be coupled to. a diverter on the wellhead pipe which comes up from the bottom. The diverter and /or blowout preventer ("BOP") can weigh about 30, 000 lbs. This is a safety device to divert or seal off any sudden rise in pressure in the conducter pipe and /or casing which can be diverted away from the drilling rigg into the mud tanks. This is also to prevent a backfire or "kick" . Such increases in pressure can, for example, be caused when the drill enters a pocket of gas .

The diverter or blowout preventer has a T-spool piece with val¬ ves . The spool piece is coupled to the pipelines that conduct the drilling mud under pressure into the mud tanks at a safe distance from the drilling rigg . The conventional way to couple the diverte to the conducter pipe is to fit two circular flanges, in the trade called API flanges, or clamp fl anges . One of them is permanently ^■ ^ fitted onto the conductorpipe and is called the starting head (bra- den head) or casing fastener. The other flange is fitted to the diverter or to the riser stack. The starting head flanges normally have between twenty and twenty four boltholes . Normally one of the flanges is welded onto the conducter pipe whilst the other one is bolted onto the riser stack or the diverter. Because of the weig

and size of the diverter to be fitted to the wellhead it is both difficult and time-consuming to bring the two flanges into posi¬ tion and join them together. Both sets of boltholes on the respec¬ tive flanges must be directed in axiaily and rotationally and held in the correct position so that the bolts can be entered into the holes and fastened. This procedure is extremely time-consuming.

The diverter may weigh about 30,000Ibs . which makes it difficult to direct and attach the diverter / riser stack to the wellhead. In addition, the API flanges or clamp flanges used to join the wellhea riser stack to the diverter system are very expensive. Nor is it desirable for this type of flange to be permanently attached to the wellhead.

Present technology presents no alternative to the use of circular flanges or clamp flanges as mentioned above. In other areas, for example in submarine drilling, the joining process is accomplished by other means. For example, in Johnson's U .S . Patent No. 3.155. a diverter is lowered onto a submarine wellhead which has a slanti base. The base is formed so that it is axiaily placed in relation to a corresponding surface on a drilling cap under the diverter. How ever, the Johnson system must be directed in with a special rota¬ tion so that a bypass conduit can be joined to a special point on the lower part of the diverter and to the corresponding lower part in the base. Thus, the same problem arises as in onshore drilling, relating to the rotational positioning as described above.

As regards the installation of pipes, several systems have been developed permitting rapid coupling and detachment. None of the present systems is adaptable to well drilling operations, especially when the weight involved is of such a magnitude as has become nor mal in the drilling business. Laskos' U .S. Patent No. 3.781 .041 , for example, describes a pipe part that joins two pipes by using a series of bolts in an angled bend that fits into a circular track on a cylindrical surface and which holds two pipes together. Lasko method also includes an elastic seal which forms an inner conical surface. However, as the surface this creates is made of compres¬ sible and elastic material, Laskos' patent is unsuitable as a connec¬ ting link between diverter/riser stack and/or the conductor pipe in the wellhead. Moreover, the seal has an elastic flange which wo

make rotational installation very difficult due to the weight. The cylindrical parts under the seal will make the axial positioning of the two pipe ends difficult, should the device be used in connec¬ tion with well drilling .

Another example of the type of rapid coupling used in pipe adjust¬ ment is described in Dickey's U .S . Patent No. 3.633.948. This coupling uses a cam operated by a lever which fits into a circular track on an otherwise smooth cylindrical surface. As mentioned previously in connection with Laskos' patent, this device is not suitable for attaching a wellhead to a diverter/riser stack because sylindrical surfaces with smooth walls are not axiaily self-adjusting they must be guided in exactly, before coupling is effected . Other examples of coupling described by Dickey are Godalls U .S . Patent No. 4.295.670, Ledstrom (3.860.274) and Krapp (2.757.944) .

None of the known systems and devices described above relates to the special problems that occur in well drilling, for example in oilfields onshore and offshore. Conditions making word diffi¬ cult can be, for example, that cement of drilling mud. clings to the pipes, joints and valves, thereby creating the need to protect expensive parts of a diverter-wellhead coupling . The time spent coupling the diverter/riser stack and the wellhead under difficult conditions, together with the need to position the diverter/riser stack to enable positioning of the parts and the outlets in speci¬ fic directions are other factors that cause difficulties. In addition, there are the very high working pressures and the possible need to switch over to conventional coupling in case of emergency. The last-mentioned problems have not been solved by our present tech nology relating to well drilling.

The rapid coupling involved in the invention makes it possible to surmount the special problems relating to well drilling. The in¬ vention involves coupling the diverter and /or riser stack and /or blowout preventer in a secure, simple, economic and appropriate way, and which leads to a considerable saving of time and work. The coupling unit is not dependent on the prior exact axial posi¬ tioning and it can be easily installed and dismantled . The inven¬ tion eliminates the need to install and leave expensive flanges or clamp flanges on the wellhead. The invention comprises several

parts. A hollow cylinder called the starting head is mounted onto the wellhead's conductor pipe, which is normally formed as a pipe with a diameter between 13" and 36" . The starting head is constructed so as to fit over the conductor pipe and is welded into place. The remainder of the starting head is formed as a pin to fit into the next part of the system which consists of a sleeve that can be lowered over the pin.

The male part of the rapid coupling can thereby be moved from wellhead to wellhead, as desired. The construction of the rapid coupling makes it unnecessary to install it permanently, neither to the wellhead, the riser stack, the blowout preventer, nor to other coupling parts.

The female part of the rapid coupling can however be permanently installed on the riser stack, the blowout preventer and /or the di¬ verter. This means that when the female part of the rapid coup¬ ling is bolted into place on the riser stack, the blowout preventer or diverter by means of flanges or clamp flanges it will remain flanged or clamped in place so that it does not have to be bolted or flanged for every subsequent operation .

When the male part of the rapid coupling has been flanged or bolt onto a particular part , the dependent female part can quite simply be lowered onto the male part of the system by crane or hoist. T frustoconical self-adjusting arrangement with male and female part ensures that the two units of the rapid coupling fit easily into eac other while at the same time adjusting themselves axiaily. They ca then be adjusted evenly in the rotation direction and be quickly secured by means of locking mechanisms.

One of the aims of the invention is to facilitate couplings between the wellhead, the riser stack, the blowout preventer and the dive without the need for exact rotational and axial adjustment.

According to the invention, expensive flanges or clamp flanges are not left behind on all the joints in the assembly and dismant¬ ling procedures connected to drilling operations.

According to the invention, the rapid coupling system can be quic

ly adapted to the remaining parts of a conventional coupling system.

The rapid coupling system. In accordance with the invention, is shown on the accompanying diagrams :

- fig . 1 shows a longitudinal section of the riser stack with pressurised air cylinders mounted .

- overhead fig . 2 shows the coupling of pipe parts onto the mounted pressurised air cylinders in longitudinal section .

- fig. 3 shows the pressurised air cylinders in longitudinal section .

A multiple riser stack assembly, consisting of several joints ( 1 ) is fitted to a wellhead conductor pipe (2) , normally of standard size, 13 inches to 36 inches rn diameter. The conductor pipe (2) reaches down to the base and functions as the main start pipe for the drilling operation. A starting head (3) is fiyed onto the conductor pipe (2) . The starting head (3) is a hollow cylinder that can be lifted by chain winches,, pressurised air hoists or other lifting devices. The starting head (3) also consists of an outer female end part (4) sealed by a metal-to-metal seal (5) and also an elastic circular seal (6) . The riser stack assembly is a hollow cylinder with a rapid coupling unit on the lower part and openings (7) where a suitable valve mechanism (8) can be fitted. The valves (8) can, for example, conduct ordinary fluids out of the system when pipes are to be dismantled.

The upper part (9) of the starting head (3) consists of a male part with an outer track ( 10) that fits onto an internal part of the riser stack's next female part. ι The male part (9) of the rapid coupling has, as mentioned, an outer metal contact surface with a circular track ( 10) . The track

( 10) has a shape and dimension which permits the end part ( 12) of the locking mechanism ( 13) to fasten onto the track ( 10) .

The contact surface of the male part (9) is adapted so as to fit in to the female part ( 1 1 ) of the rapid coupling .

The female part ( 11 ) is a hollow cylinder with inner metal surfaces formed like an amputated cone. It fits together with the opposite surface, which ensures that the two surfaces adjust to each other axiaily on coupling, due to the effect of gravity. The female part ( 1 1 ) also has a set of locking devices ( 13) that are threaded in through radial holes ( 14) . The contact surfaces on the male (9) and female ( 11 ) parts are bevelled at their respective ends to reduce friction as much as possible on coupling.

In actual use, the female part ( 11 ) of the rapid coupling is more or less permanently joined to the diverter ( 18) through one or more external parts ( 14 and 15) joined on coupling according to the invention. When the diverter ( 18) is finally fitted with its fe¬ male part (17) the remaining parts are lowered and it is quickly coupled to them . This is made possible because the non-elastic semiconically shaped surfaces of the; omplementary parts ( 17 : and of the rapid coupling ensure the automatic axial adjustment of the two parts that are to be fitted together.

Fig. 2 shows the locking device in detail . The preferred number of locking units in each rapid coupling is nine. Experience has shown that nine is the smallest number of locking devices ( 13) needed if a rapid coupling is to withstand working pressures of realistic dimensions. The number of locking devices can however be freely varied, depending on requirements. The rapid coupling is sealed with the help of a metal packing ring (5) and also by a disc packing ring (6) . The metal packing ring lies on the upper part (9) and the elastic packing ring (6) is placed alongside the pin over the locking track (10) .

Each locking device, as shown in fig. 2, can consist of a hydrau¬ lic or pneumatic cylinder ( 13) mounted in a rapidly drilled hole ( 1 in the female part of the rapid coupling . The thread or pin part has a conical end part which fits into the circular track ( 10) . The locking devices (13) are also formed so that they can be screwed in and out manually. The locking device is operated by the appli¬ cation of hydraulic or pneumatic pressure through the nippel (19) The locking device (13) therefore consists of a hydraulic or pneu¬ matic cylinder in accordance with known techniques with a piston (20) , pressure cylinder (21 ) , springs (22) and locking element ( 1

The locking element (12) is connected to the piston (20) so that the locking element (12) is directly connected to the piston (20), which means that the locking element (12) locks into the circular track (10) when the piston (29) is completely compressed by the coil springs. In fig. 2 there is no pressure in the pressur chamber (21) and the piston (20) is therefore pressed right up to the end wall of the pressure chamber (21).

When the pressure chamber (21) is put under pressure the spring (22) will yield elastically, so that the piston (20) is moved by in¬ creasing pressure, bringing the locking element (12) with it. The locking element (12) therefore no longer locks into the circular track (10).