The present invention relates to a device for providing a pressure pulse for activating fluid pressure activated equipment in a fluid conveying pipe, where a section of the pipe wall includes a number of penetrating bores, and flexible membrane is arranged on the outside of the pipe section, said flexible membrane isolating a first fluid F1 in the fluid-conveying pipe from a second fluid F2 in another canal which is in fluidic communication with the equipment, wherein the membrane, on account of its elasticity, conveys pressure changes (pressure pulses) in the fluid F1 in the pipe to the fluid F2 in the other canal, as defined in the preamble of the appended claim 1.

In particular, the invention is concerned with a construction which is capable of supporting operation of down-hole equipment which is hydraulically operated.

It has been well known for a long time that, in connection with pressure-pulse activation of mechanical equipment installed down in an oil- or gas-well, there are challenges related to convey theses pressure pulses forward to the equipment.

This is especially pertinent when a pipe which is introduced down into the well is pressurized up to transmit these pressure signals down to the equipment. A problem that is that is often encountered is that, over time, there is formed an accumulation of particles in liquid, which eventually forms a solid mass at a bottom of the pipe, when such particles sink to the bottom. This is especially a problem when plugs are employed in the production pipe which operates in a manner to pump up pressure over the plug from the rig.

A manner of limiting the problem is to couple the equipment via a hydraulic control line (a conductor) which is disposed outside the existing pipe wherein the plug is mounted. Such a control lines are routed upwards and through the wellhead-installation and further up to the rig, such that it can be subject to pressure directly from the rig, and as a consequence one is still able to operate the equipment despite an accumulation of mud over the plug in the pipe.

The disadvantage of such a system is that, to a major extent, it renders operation more expensive and establishing a several kilometer long control line (conductor) introduces a risk that it is possible that the pipe which generally, for example, is a thin tube with a dimension ¼" (6.3 mm) is worn against walls of the well, and it is thereby possible to lose all control of the equipment.

A known solution is to use an kind of accumulator for introducing clean liquid into the well. Such a solution is described in Norwegian patent application no. 2008 0452. There is described an accumulator which includes a limited volume for supplying the equipment with clean liquid for operating it.

That which is described in said Norwegian patent application is a piston accumulator which pursuant to the description accumulates pressure during introduction into the well.

This system continues to result in a considerable number of problems associated with functionality.

First and foremost, it is claimed that debris (supply of contamination) are not able to penetrate into the system. But such a claim is incorrect, on account of it being known that a blockage of the canal upstream of the piston, as described, would not be able to convey the pressure pulses which are necessary for the system to function. It is correct that these particles would not be able to contaminate downstream of the piston which is to actuate the cyclic mechanism in the system, which is operable to open depending on a beforehand specified number of pressure pulses. The problem is namely that, by way of liquid communication through the canal up-stream for the piston, particles may enter into the chamber and thereby block the piston from moving, such that pressure differences can arise between upstream and downstream of the piston.

A cyclical-system which is based upon pressure differences would then cease to function.

In respect of the state-of-the-art, reference is also made to US patents Nos. US-2,964,116, US-2,898,088 and US-4.436.164.

In this respect, US-2,964,116 discloses a pressure pulse signalling system in a drill string, wherein a membrane in the form of a sleeve is placed on a perforated pipe section. The membrane transmits pressure pulses from a drilling fluid to a hydraulic fluid in a chamber, surrounding the perforated pipe section, to a conduit, and further to a pressure actuated equipment, as shown in column 4, lines 21-53, column 8, lines 15-20 and on figures 1 a and 2. US-2,898,088 shows a borehole logging system, incorporating a pipe section with a flexible, sleeve shaped membrane, which separates a fluid in the drill pipe form a hydraulic fluid in an outer chamber and in a conduit, the latter being connected to a fluid pressure actuated equipment. Thus, the membrane transmits fluid pressure pulses from the fluid in the drill pipe to the pressure controlled equipment.

It is a principal object of the invention to provide a new construction which is capable of solving the aforementioned disadvantages and problems.

The device pursuant to the present invention is characterized in that each bore through the pipe section wall defines a central concentric bore, in that each end of the bore forms a conical extension towards the inner wall and the outer wall of the pipe section, respectively.

The beneficial implementations appear in the dependent claims 2 to 8.

An advantage of this solution of having conical extended bores is that each hole is not so easily blocked permanently by slime and particles. A particle in the pipe fluid, which may bind and block the entrance to the bored hole will simply loosen and be pushed back again when the fluid flow is reversed. The particle will then be easier to be loosened by the back flow.

One of the advantages of the present invention, as defined, is that a piston which moves axial in a longitudinal direction will be limited in area which can be affected, whereas a bellows which moves radially is capable of providing an enormous area which can be affected. This area is limited only by the length of the bellow.

The present invention will now be described in more detail with reference to the accompanying diagrams.

• Figure 1 is an illustration of a pipe which is installed within a borehole in, for example, a hydrocarbon-bearing formation, wherein the inventive device is employed.
• Figures 2 and 3 are illustrations of the details of the inventive construction 10 in two positions, in that it is disposed a distance upstream in respect of down-hole equipment 20 which is be operated hydraulically pursuant to the present invention.
• Figure 3B is an illustration of an elongate cross-section of a hole which is arranged in a radial direction through the pipe wall.
• Figures 4 and 5 are illustrations of an enlarged portion of Figures 2 and Figure 3, and illustrates the hydraulic canal 30 through the pipe wall and which couples the pressure pulse device 10 with the equipment 20.

The Figures provide illustrations of a pipe 12 which is deployed in a borehole 14 in a formation 16. Described as a non-limiting example, a pipe section 18 is installed at a lowest portion of the pipe 12 with a seat accommodating a plug 22. The plug 22 is used, for example, initially for testing and checking that the interior of the pipe is sufficient non-leaky under pressure, and will function as intended during production of hydrocarbons from the formation 16.

As a consequence of the upwardly-facing surface of the plug 23 being susceptible to collecting large deposits 25 of contamination comprising solid particles such as slime, the device 10 is positioned a distance up over the plug 20, and the plug 20 and device 10 are mutually coupled via a canal 30 which extends axially along and through the wall of the pipe between these two regions.

The device includes a perforated pipe section 27 which is installed into the pipe 12. A hollow volume or chamber 26 is defined between the outer wall 21 of the section and the inner wall of the pipe 12.

Surrounding the pipe section 25 is threaded a sleeve-shaped elastic bellows or membrane 24, and uppermost at 31 and lowermost at 33 is attached in the solid material of the pipe section 25. The bellows 24 can subsequently bulge out from a position where in lies bonded onto the pipe section's outer wall 21 and to an extent it bulges out and lies against the inner wall 13. Outside the bellows 24 is a ring-shaped chamber 26 coupled with a drilled canal 30 which extends through the pipe wall downwardly to the release mechanism (not especially shown here) which is used to explode the plug away.

The bellow's position or bulging will be dependent upon a difference in a pressure P1 within the pipe 12 and a pressure P2 in the chamber or the canal 30 outside the membrane 24. Figure 2 illustrates the situation where the pressure P1 is higher than the pressure P2 (P1 > P2) such that the membrane bulges out.

Figure 3 is an illustration of a situation wherein the pressure P2 is higher or equal to the pressure P1 and the membrane lies in a wavy manner against the outer wall 21.

A release mechanism which removes the plug is adapted such that it counts a number of pulses, wherein the pulses are generated by increasing and decreasing the fluid pressure P1, and wherein the plug is exploded away at a predetermined number of pulses.

In the chamber radially outside the bellows, there is filled a clean liquid which is present in connection with an outside lying pipe or the internally bored canal 30 which again is present in connection with, for example, a pressure-pulse sensitive valve.

The pressure-sensitive valve can be set, or be set up, either to read the signals electronically with help of a pressure transmitter, or it can be a purely mechanical system which reads pressure pulses for opening the valve at a predetermined number of pressure pulses.

When the valve opens, the clean liquid flows past the valve and operates the equipment which is hydraulically operated. The technology can be used to operate down-borehole equipment which is hydraulically operated, and requires clean liquid for operating correctly. Examples of such equipment can be detonation systems for removable (disappearing) plugs, sliding sleeves, hydraulically operated ball valves and hydraulically-operated flapper valves. These are only some few example of equipment with which this new technological solution can be utilized. The hydraulically operated system can for example be a layer-divided plug 22 fabricated from glass. In whatever manner it is removed or smashed is not specifically shown in the Figures. The pressure-pulse controlled apparatus can include A device 39 which is operable the count the number of pulses, and when it has counted a correct number, the mechanism is activated and releases an explosive mechanism. This can, for example, mean that an axially-disposed piston 38 in the pipe wall is pushed downwardly with large force and slides a horizontally-orientated smashing piston in a radial direction and into the plug 22 which thereby can be smashed. The plug can be fabricated from ceramics materials which can be smashed or from glass which is adapted for this purpose.

By utilizing a bellows instead of a piston, it is also possible to bore a large number of holes radially through the wall around the periphery of the protective collar which supports the bellow and maintains the clean liquid in place. An elongate cross-section of these bored out holes 50 in a radial direction through the pipe wall 26, is shown in cross-section in Figure 3B. On both sides thereof (from each end thereof), there is bored out a hole through the wall. The central portion of the hole through the wall beneficially has a form of a bored out region 56 with circular cross-section, whereas each end of the circular bore continue with a gradually increasing cross-section diameter towards the wall surfaces, namely showing a conical form. The bored out region is of course widest out towards the wall surfaces, namely the form of holes 52 to 54 shown in the diagrams are such that that the outermost form respectively cone-shaped form or conically formed holes, or substantially of trumpet-form. These bores can have other cross-sections than circular. An advantage with this form of hole is that each hole is not so easily blocked permanently by slime and particles.

The risk that the holes with such a form can be blocked by debris and solid particles and slime can be reduced by the holes being bored out such that they are concentric in both directions. This form of hole through the wall having an expanding cross section of the bore, towards the outer wall, resulting in there being achieved an effect, wherein there will always be fluid/liquid streaming both ways as a result of particles bound in the conical hole which is opened up with largest diameter at an opposite side to that which is influenced by pressure with a result that the particles become loosened when pressure is applied from the side that has smallest hole. A particle 60 in the pipe fluid, which may bind and block the entrance to the bored hole 56, when the fluid F1 streams in a direction of the arrow P2, will simply loosen and be pushed back again when the fluid pressure P2 exceeds the fluid pressure P1 and the fluid F2 streams back. The particle 60 will then be easier to be loosened by the back streaming.

Moreover, with reference to Figures 2 and 3, there are provided a breaking plate (or several), brushing disks which are arranged to break or burst when, for example, 10 Bar pressure difference between the pressure in the clean fluid behind the flexible material and the liquid in the well pipe arising, further ensuring against there arising a pressure difference between the two liquids. The flexible membrane will also always bring about that identical pressures arise on both sides and return to its original form after a pressure excursion.

Through the wall of the pipe 27, namely above the perforated wall portion, there are bored out one (or more) holes 160 which forms a fluid connection between the ring-shaped chamber 26 outside the bellows and an inner of the pipe denotes by F1/P1 (Figures 2 and 3). In the hole, there is installed a metal plate for providing a bursting disk 162, wherein this plate is attached via an anchoring denoted by 58, such as screw or the similar on the diagrams.

The burst disk 162 is adapted for creating fluidic communication in an event that an excessive pressure is developed on the back side (P2) of the bellows, namely when the pressure is not the same as the pressure P1 within the pipe (tubing).

The bore for the break disk can, as a point of reference, be placed anywhere, as long as it stands positioned such that it separates fluid between the tubing and back side of the bellows and creates a communication path between them when it bursts.

The burst disk 162 will also provide an eventual operation of the equipment which is to be controlled by later re-filling with liquid when the clean liquid behind the membrane is consumed, wherein the membrane is pre set towards the walls in its respective housing, so that a pressure difference arises between the well pipe (P1) and the back side (P2) of the membrane, whereafter the burst disk will break and liquid from the well will thereafter pour into the system.

There are thus many advantages in comparison to known state-of-the-art which has a limited volume surfaces which can be influenced with associated risk that holes of the system become blocked in operation.