The invention can also be said to relate to a high-pressure drilling fluid cutting tool (drilling fluid shear gun) for cutting and mixing of mud. Normally in offshore oil rigs, a used drill bit with an inserted nozzle is used to achieve the desired physical properties of mud (drilling fluid). This is done in that one lets mud pass through a nozzle where it is "crushed". The pressure which is used can be up towards 200 bar, and the amount of liquid between 500 - 1000 l/min. Today's plants are constructed in such a way that this is done in drilling mud tanks which are on board the rigs, and a jet from a nozzle goes directly down into the mud in the tank. The force of the jet results in that it goes deep into the tank, and often the residual power in the jet is great when this meets the tank wall. By varying levels in the tank, residual forces will vary, and the jet is broken down by the mud level in the tank. This can result in washout of the tank wall, and also that much noise is generated. Access for maintenance of tanks and nozzles must be done by entering the tank, which is risky and time-consuming. If one gets a washout and holes in the tank wall this can result in discharges to the external environment. Challenges to the prior art are therefore linked to, among other things, noise, washout of tank walls, vulnerability to fluctuating levels in the tank, and also that the solutions are often not designed for the purpose. The present drilling fluid shear gun can be mounted into an existing process vertically, horizontally or inclined. The invention is designed with respect to it easily being mounted/dismantled while at the same time as it functions as a "double barrier", for example, in a tank wall. Furthermore, wear parts can be replaced without entering the tank and without down time in drilling, and it is easy to clean.

From prior art, reference is made to, amongst others, US 2626788 A, which describes a cylindrical installation which is mounted on a drilling fluid tank, and which is used for mixing of drilling fluids. The installation comprises a screw formed conveyor which extends from the first end of the cylinder to the other end which, in turn, is constructed to include a conical shaped part.

A further object of the invention is to provide an alternative and improved solution which reduces the time, risk and cost of maintenance operations related to a drilling mud tank, on a drilling fluid circulation system on offshore oil rigs. According to the invention, a cylindrical installation that can be mounted either into / or out of the drilling fluid tank and which provides a double barrier against the tank wall is used as an example. An object is also reduction of noise. Tests of the invention have shown that the noise is reduced from 1 13 to 79.8 dB. This one factor in itself is very positive with regard to HES. Tests have also shown that the device according to the invention cuts the mud very well, and that it thereby achieves a very good mud quality. As the outlets on the shear gun are upstream of a distribution cone, this means that the cylinder is filled with liquid and that the mud jet from the nozzle hits a bath of mud before it hits the cone/spreader and cylinder wall. It will then dampen the speed of the liquid and thereby reduce noise and wear on the cylinder shell.

Reference is also made to US 2007/084638 A1 , US 4474254 A, US 4285601 A, and US 2748884 A, as other examples of a device or installation that encompasses the use of high-pressure nozzles with or in a drilling mud tank to help with mixing of the drilling fluid in the tank. Furthermore, reference is made to WO 201 1 /142894 A1 , US 5460449 A and US 5145256 A.

The above mentioned objects achieved with a drilling fluid shear gun, comprising a housing in the form of an elongated, internally hollow body arranged to receive drilling fluid, as the housing comprises an interior space equipped with a high pressure nozzle which is connected to an inlet which extends through a first, upper part of the elongated body of the housing and an opposing distribution cone which is arranged in a second, lower part of the elongated body of the housing, wherein a number of openings or slits are provided in the upper part of the housing cavity, arranged to function as a liquid outlet for mixed drilling fluids, and that the nozzle opening of the high pressure nozzle is mounted lower than said openings or slits in the cavity of the housing. Furthermore, the inner space, at least in the area of the distribution cone, can be clad with a lining of abrasive material of a heavy metal, such as tungsten carbide. The lining can include several rings of abrasive material.

Underneath, the distribution cone can be equipped with drainage openings towards a bottom of the housing.

The high-pressure nozzle can additionally be mounted in a rigid nozzle housing.

Furthermore, at least the high pressure nozzle opening can be provided with a nozzle coat or housing.

The high-pressure nozzle and / or nozzle coat can be made from, or clad with, a heavy metal, such as tungsten carbide.

The shear gun according to the invention can be arranged to be mounted in a drilling fluid tank, or the shear gun can be arranged to be mounted upstream of the tank. The shear gun can also comprise an external mounting flange in an upper part of the housing, where the mounting flange is formed as a quick release coupling arranged to rotate for locking. Furthermore, the shear gun according to the invention can be arranged to receive drilling fluid from one or more external mud pumps to contribute to the mixing of drilling fluids and for generating pressure in the high pressure nozzle.

The invention shall now be described with the help of the accompanying figures, in which:

Figure 1 shows an outline of a drilling fluid shear gun according to the invention.

Figure 2 shows a section of a shear gun according to the invention.

Figures 3 and 4 show an enlarged embodiment of the shear gun according to the invention.

Figure 5 shows illustratively the shear gun according to the invention mounted in a drilling fluid tank.

Figure 6 shows illustratively the mounting of the shear gun according to the invention to a deck or on a drilling fluid tank.

As can be seen from figures 1 and 2, the invention comprises a shear gun or installation 10 comprising a housing 12 in the form of an elongated body. The housing 12 can have a circular, cylindrical shape with an internal, hollow space 16. The shear gun 10, in one embodiment, is arranged for mounting in a drilling fluid tank and, for this reason, is preferably equipped with an exterior mounting flange 14 in an upper part of the housing 12. The elongated body of the housing 12 is further equipped with openings or slits 18 which function as liquid outlets for drilling fluid from the internal space 16, where said openings or slits 18 are located in a first, upper part of the internal cavity 16 in the upper part of the housing 12. The openings or the slits 18 can also serve to regulate the amount of drilling fluid in the internal space 16. The exterior mounting flange14 in the upper part of the housing 12 can have one or two flanges for adaptation to the rig it is to be used on. If it is desirable that the equipment be made lower, it can be adapted by the use of a flange, while

alternatively two flanges can be used, as shown in figure 1 . Due to lack of space on a rig, the middle piece 14a on the top of the flange can be removed, for example. Alternatively, the height between the two top flanges can be varied depending on the tank design and space for fastening. Furthermore, the mounting flange 14 can comprise lifting lobes 15, as shown in figure 6. The mounting flange 14 can also be designed as a quick release coupling, i.e.

without the use of bolts for fastening. The shear gun 10 is then set down on the top of the tank and is rotated clockwise, for example, 0-270 degrees to lock it in that the mounting flange engages the locking groove. The same procedure is used in reverse to release it.

Figure 2 shows in more detail the embodiment shown in figure 1 inside. As it shows, a first end or part of the elongated body of the housing 12 comprises an inlet 28, and as in the embodiment shown it is in an upper portion of the elongated body 12. The inlet is preferably connected to existing equipment, such as external mud pumps 50. The pumps will also supply the required pressure on the fluid in the shear gun 10. About the inlet 28, a rigid nozzle housing 30 can be mounted, and which can accommodate a high pressure nozzle 20. The nozzle housing 30 can be in the form of rigid plates or the like and be equipped with a mounting plate 30a, as shown in figure 3. In the mounting of the nozzle housing 30 in the space 16 in the elongated body 12, the mounting plate 30a can be screwed permanently to, for example, the mounting flange 14 with the help of bolts.

About the high pressure nozzle 20, a nozzle coat or housing 32 can be mounted. The housing 32 at the outlet of the nozzle 20 has the aim of reducing noise. It also eliminates the possibility of washing out of tanks, providing a double barrier, equivalent to the housing 12. It also gives the possibility of cutting mud regardless of the level in the tank. The nozzle housing, in general, leads to an increased lifespan for the equipment.

When one starts cutting/mixing of drilling fluids such as mud, the housing, i.e. the space 16, will fill up and will thus keep a level in the housing 12. Cut mud flows out in the overflow recesses in the form of the slits or the openings 18. When one cuts mud, forces that develop in the high pressure nozzle will naturally be transmitted to the media/wall of the housing 1 2. At a given level the residual forces are negligible, since the mud absorbs all forces. Because of the high speeds of mud, the nozzle/ housing/drainage are preferably clad with a heavy metal, such as tungsten carbide. This serves to increase longevity.

The term "mixture" must be understood to include what is normally understood in connection with the term "cutting". Furthermore, the terms "upper" and "lower" must be understood such as the parts are shown in the figures.

At the other end of the elongated body of the housing 12, a distribution cone 22 is arranged, i.e. the cone 22 is located opposite to the high pressure nozzle 20, which in the illustrated embodiment, is in a lower part of the elongated body 12. The purpose of the cone is to distribute drilling fluid in the space 16, so that the

aforementioned disadvantages do not occur. The cone 22 can have a conical shape, a tapering shape or, for that matter, a form corresponding to that of a "Chinese hat"

In the internal space 16, at least in the area about the distribution cone 22 and against or towards the high pressure nozzle 20, the room is preferably clad with a lining 34 of a abrasive material, such as tungsten carbide. This lining 34 can be replaceable. As shown in figure 4, the lining 34 can comprise a number of rings which are mounted in the internal space 16, and by selecting the number of rings it can be ensured that all areas susceptible to wear are protected.

Under or adjoining the distribution cone 22, drainage can be provided in the form of drainage openings 24 towards an end bottom 26 of the housing 12. The drainage that is at the bottom of the housing has, in addition, the aim of providing less weight to the equipment when it is not in use, since it can be emptied. It allows easier cleaning, for example, by replacing mud types (water based/oil based mud). The design of the drainage will also reduce any residual forces against the bottom. The drainage can also be provided in places other than those shown in the figure.

In the illustrated embodiment of a shear gun 10 according to the invention, as the example shown in figure 5, it is immersed in a tank 40 for drilling fluid. The fluid is not taken from the tank, but is supplied to the tank 40 via the present shear gun 10, i.e. that the liquid comes from a different process before it ends up in the tank, for example, from existing mud pumps 50 via pipelines 52. When the tank 40 is filled up, the shear gun will also be filled up so that the liquid level will dampen some of the pressure before it hits the wall. When the tank 40 is drained, the present shear gun will also be drained since it has openings in the bottom. Normally there is a system which takes the liquid further to another tank when it is full. This is to ensure that the tanks are not overfilled. This is usually automatically controlled with level gauges and an overflow. The drilling fluid tank 40 can also be equipped with an agitator connected to a drive motor.

Figure 6 shows the shear gun 10 according to the invention mounted to a deck 42, for example, the top of the tank 40 or another suitable location. The pipeline 52 is connected to the inlet 28 in the nozzle housing 30 via a coupling piece 46, where the coupling piece can be designed to produce a reducing or equalizing effect on the fluid flow. The mounting flange 14, shown here with lifting lobes 15, can be mounted to a rigid plate 44 which, for example, is welded permanently to the deck 42.

In a second embodiment (not shown), the shear gun 10 can be arranged for mounting upstream of the tank, for example, on a straight stretch of piping. This will simplify the access and monitoring of conditions, and reduce noise levels. The drilling fluid shear gun according to the invention can also be mounted in any process line (before the tank) and thus deliver treated drilling fluid to several tanks if desired. In the latter case, said slits or openings can be in the form of an outlet, readily in the form of a manifold, which can control the distribution of drilling fluid via valves.

Replaceable parts are preferably made of a suitable material (hard metals or ceramics, heavy metal such as tungsten carbide) for long life, and they can be easily replaced without entering the tank, which gives easier maintenance and control. Furthermore, sealing rings or gaskets can be used between the assembled parts.