WO2009116871A1

WO2009116871A1 - Device of a plug for well testing

Info

Publication number: WO2009116871A1
Application number: PCT/NO2009/000080
Authority: WO
Inventors: Viggo Brandsdal; Sigmund Sevatdal; Kare Olav Krogenes
Original assignee: Tco As
Priority date: 2008-03-07
Filing date: 2009-03-09
Publication date: 2009-09-24
Also published as: NO20081229L

Abstract

The invention comprises a device of a plug for conducting tests in a well, pipe or similar, comprising a plug element made of a disintegrateable/ breakable material. The device is characterized by an organ that is arranged to move radially and cause an impact against the plug by movement of a trigger element (2) in axial direction, in which the radial movement causes the breaking of the plug element. The organ preferably consists of one or more taps (2) arranged to move radially, and the trigger mechanism and the tap are built in the wall of a pipe sleeve (12). The sleeve consists of a boring (17, 20) for one or more axially oriented pistons arranged to move the tap (2) radially. The plug is preferably made of glass and the sidewall-surface consists of a frosted-glass area where the tap (2) can do the impact.

Description

DEVICEOF A PLUG FORWELL TESTING

The present patent application relates to a device for a plug for conducting tests of a well, a pipe or the like, comprising a plug element of disintegrateable/crushable material, as can be seen in the introduction to claim 1.

In a well or a drill hole in a hydrocarbon-carrying formation, it is well known to close off all passage of fluid to test that all parts of the well are sufficiently leak proof and can retain a given fluid pressure, before the well is taken into use for the production of hydrocarbons. For this purpose, a plug of glass or a ceramic material is temporarily mounted in the pipe. Thereafter, a fluid is forced up into the well to test that it is sufficiently leak proof.

When the testing is completed, the plug is removed, for example by using explosive charges that are mounted on or at the plug, or by carrying out a mechanical crushing.

As a rule, such explosive charges are placed on the top of the plug. But they can, in some cases, also be placed in the centre of the plug. Many mechanisms can be used to set off such explosive charges.

Removing such plugs without the use of explosives is also known, by crushing it using mechanical influences, such as administering blows. Such crushing can also take place by increasing the pressure in the well to values so high that the plug ruptures.

Today's systems with explosive charges does however give unwanted large, loose fragments in the well after the explosion. Furthermore, the explosives are in themselves a potential risk which is unwanted by the customers. In addition, there is also a theoretical possibility that parts of the explosives can be live or undetonated after the plug has been blown apart.

It is also a problem, and is gradually becoming unacceptable for the users, that the plugs in themselves contain integrated explosives which can constitute a risk.

In those cases where several plug elements are placed on top of each other with liquid in between each element a corresponding effect can also be obtained, namely crushing without the use of explosives. This solution is based on that the controlled fluid between the plug elements can not be compressed and through this the uppermost plug element will get aid to take the axial load of the system off the below lying elements.

With this system one will be vulnerable to dropping things down in the well that break the upper plug element which on its own can not withstand large mechanical loads. The consequence of this wi 11 be that the plug opens at a point in time when it will be very unfortunate. One is also vulnerable to any fluid in between the plug elements leaking out as this will also lead to the plug opening too early.

It is also undesired with such a solution that in order to be sure of that the plug ruptures after the liquid between the elements is drained out in a controlled way, one must have plug elements of such thickness that they are crushed at moderate pressures.

It is an aim of the invention to eliminate the above mentioned disadvantages.

The device for the plug according to the invention is characterised in that it comprises a element arranged to move radially by driving a release element in the axial direction, where said radial movement leads to the crushing effect on the plug element.

According to a preferred embodiment, the element comprises one or more pegs that can move radially, and the release mechanism and the peg are built into the wall of the pipe casing that carries the plug.

According to yet another preferred embodiment the pipe casing comprises a boring for one or more pistons that can actually influence the peg or pegs to move radially.

According to yet another preferred embodiment, the one or more pistons are spring loaded and move axially when released. According to yet another preferred embodiment the pistons move vertically on the release with aid of the spring and hit the peg at the back, and through its wedge shape the peg is forced into the plug element which is then crushed.

According to yet another preferred embodiment the pistons and the springs are fitted in a boring/borings (a channel) in a casing which is fitted inside the pipe casing.

According to yet another preferred embodiment the casing comprises the release mechanism which comprises the valve, which on activation or opening lets in pressure fluid and thereby releases the piston and the spring so that these move axially downwards and hit the peg, which thereby is pushed in the radial direction to crush the plug.

According to yet another preferred embodiment the release mechanism reads pressure pulses in the pipe by aid of a mechanical, acoustic, electrical, ultrasound or hydraulic reading, and opens the valve 6 when the correct signal is received.

According to yet another preferred embodiment, a lower part of the piston is cut at an angle or pointed to form a pin, when this is pushed downwards, a peg is pushed radially inwards so that its point is forced into the plug element, whereby said axial movement is transformed into a radial movement.

The element preferably comprises one or more pegs that can move radially and the release mechanism, and the pegs are built into the plug wall. According to a preferred embodiment, the plug comprises a boring to one or more axial pistons that influence the peg or pegs radially.

The invention relates to removal of plugs without the use of explosives. It preferably comprises an axially arranged spring loaded piston that is released by a release mechanism.

Preferably, this piston hits one or more radially arranged pins which, when influenced by the piston, move axially in toward the centre of the plug. These pins are preferably fitted with a hard metal tip that buries into the plug material which will then be crushed. The preferred embodiments appear in the dependent claims 2-9.

When such a system with mechanical crushing is used, one avoids the problems with explosives and the associated safety risks. One also avoids all the remains of housings that hold the explosives in the well. This will represent a considerable improvement of crushable plugs for all types of wells.

Crushing of the plug by applying the radial force from the side has been tested and gives very good results when one uses plugs made from glass or other ceramic materials. It is also an essential feature of the invention that the crushing can occur from the side. When the main parts of the release mechanism are arranged in the pipe wall one does not take up too much of the inner diameter of the well.

It is a great advantage that with the present invention one can avoid the use of explosive charges.

According to the invention one obtains an especially favourable effect when the glass plug comprises so called "slip" around the circumference so that the glass material in the plug already contains minute cracks 110 that stretch from the surface and a distance into the glass material. The slip is also called "frosted glass" and comprises that the surface is made rough in that it is ground, for example, with a file so that the surface becomes milky white. Such a surface treatment also leads to the formation of said minute cracks just below the surface. Slip is often used in connection with sealing of plugs of glass where the slip is lubricated with glycerine, with such plugs often being called "greased plugs".

A pointed crushing element that is forced into the sides of the glass will cause these minute cracks to expand such that the plug ruptures more easily and is pulverised in the same way as the window of a car when crushed.

The present invention is also much less costly to produce as one removes the costly component explosives represent. Transport and logistics will also be much simpler, also as one does not need to take into consideration that there are explosives in the plug- containing elements.

The mechanism according to the present invention consequently functions in that an axial force in a compressed spring released by either an electric signal, ultrasound, acoustic or hydraulic pulses in a well sensed by a mechanical or electric system is transformed into a radial, mechanical movement that forces one or more pointed pegs into the plug. When this radial movement is started, the plug element breaks up the minute cracks and the increased formation of cracks results in the collapse of the plug under the well pressure.

In the following, the invention shall now be explained in more detail with reference to the enclosed figures, in which:

Figure 1 shows the application area for the invention.

Figure 2 shows a longitudinal vertical section of the construction of the plug section according to the invention including the release mechanism for crushing of the plug, encompassing a compressed spring.

Figure 3 shows the construction according to figure 2 where the spring force is released and a peg is made to push into the plug so that it is crushed.

Figure 4 shows details of the mechanism in an enlarged longitudinal cross section.

Figure 5 shows in perspective an example of a glass plug with a "frosted glass" surface.

Figure 1 shows an installation in the form of a platform 140 which operates the production from a hydrocarbon-carrying formation 100. The reference number 130 indicates a seabed, while a sea surface is shown by 150. Acasing 10 runs through the hydrocarbon-carrying formation 100, said casing shall be tested with the aid of the plug section according to the present invention.

A plug 7 is fitted inside a tube bundle 11 that is inserted in the casing 10 in the well 19 which runs through the formation 100. The plug is inserted to temporarily close off for fluid streams, such as during pressure testing of the well 19, to ensure that all parts of this is sufficiently seal proof and can retain a given pressure. The plug is preferably shaped as a circle-shaped disc of a given radius and thickness/height, as shown in figure 5. The circular side surface 71 of the plug is made to be rough (shown by dots) in that it is ground so that it has a milky-white colour and is not transparent. By grinding the surface so that a number of minute cracks 110 are formed from the surface and into the material, and said minute cracks do not reduce the ability of the plug during pressure testing.

The figures 2, 3 and 4 show in more detail the construction of the pipe bundle 11 which holds the plug 7.

Figure 2 shows that a casing 12 that holds the release mechanism itself (piston and peg) that will remove the plug 7 when the pressure testing is completed is inserted in the pipe bundle 11. The plug 7 is fitted in a seat 15 in the lower internal part of the casing 12 which in turn is held in place in the pipe bundle with the aid of a nut 16.

The casing 12 comprises a channel 5 that runs axially from the top of the casing 12. The channel forms a fluid connection with the well fluid on the top 19 of the plug.

A plug or a peg 2 with a pointed end 42 which is intended for the crushing of the plug 7 is located adjacent to the plug at the bottom end of the channel 5.

The channel 5 contains a valve 6 at the inlet of the channel 5, and below the valve the channel is enlarged (at 20) and holds a spring that is compressed with the aid of the top side of an extended piston 3 which in turn is held back into the upper part of the casing 12 (in its upper position) with the aid of one or more shear pins 14 that extend into the wall that defines the channel 5 and into the piston 3.

The casing 12 can contain one or more such held back pistons 3, with the figures showing two such units.

The lower part of the piston 3 preferably comprises a pin 40, cut at an angle or with a pointed end, see especially figure 4. When the pin is pushed downwards, it will lead to the peg 23 being pushed radially inwards so that its point 42 is pushed into the plug element. The surface that is cut at an angle is shown by 43 in figure 4. An axial movement of the piston 3 is consequently made into a radial movement of the peg 23.

The spring 1 is held in a compressed position by the shear pin 14 until the valve 6 opens. When the valve 6 opens for hyd rostatic pressure from the top side 19 of the plug, fluid flows under pressure through the channel 5 and into the hollow space 20 and the force on the shear pin(s) 14 is so great so that the pin breaks and the piston 3 shoots downwards and reinforces the force from the spring 1 which is released. Valve 6 is a shape of the type which senses pressure pulses in the well 19 injected from the top side of the plug element 7. This valve will then open for the pressure after having received a correct number of pressure pulses inserted at the top the plug element 7.

The pressure pulses arise from the testing of the well where the fluid pressure on the top side of the plug 7 is alternatingly increased and decreased.

The piston 3 and the shear pin 14 comprise a sealing element 9 to obtain a pressure tight chamber 17 and chamber 20 in the fluid channel. The chamber 17 is the volume of the channel lying around and below the piston, while the chamber 20 makes up the channel part in which the spring 1 is taken up i.e. above the piston 3. The nut 16 comprises through holes to let in well pressure to the valve 6. The casing 12 also contains a sealing element 8,13,22 to make sure the chambers 17 and 20 are pressure tight. The plug is sealed against the seat 15 of the casing 11 with the aid of sealing elements 22 that also have as the main task of holding the pressure from the well side 18 of the plug 7 (i.e. at the underside of the plug). When the piston 3 is released to the axial downwards movement with the aid of the pressure fluid that flows in through the valve 6, the peg 2 is forced in a radial direction in to the plug element 7. The peg 2 has a pointed end and the point has a hard metal peg 23 which helps to open the minute cracks 10 (see the figures 3 and 4) that are present in the plug element 7 and which extend from the plug surface and a distance into the glass element.

Initially, the piston 3 can be displaced only with the use of the fluid pressure that is let through the valve, with the spring 1 functioning as an addition to ensure a sufficiently powerful blow against the plug.

When the peg 2 is forced into the plug element 7 the minute cracks escalate and the plug ruptures and is crushed to small pieces as a consequence of the inner tensions in the plug element 7.

The peg 2 is rounded at the rear end and protrudes into the hollow space 17 before being activated by the piston 3. When the piston 3, with its wedge shaped lower part 40,43 then hits the peg 2, the downwards axial force is transferred to a radial force on the peg 2 which is then displaced in a radial direction in towards the centre of the plug According to the invention it is preferred (it is most practical) that the piston 2 gets its pushing power downwards from the compressed spring 1.

However, the compressed spring 1 can be replaced by a cartridge with a compressed gas that functions such that at a release signal, i.e. when the pressure fluid is let in through the channel 5 by the opening of the valve 6, the gas is released in the form of a powerful high-pressure pulse so that the piston is forced downwards.

According to the invention it is preferred that the boring for the one or more pegs 2 is arranged horizontally in the casing 12 around its circumference, but they can also be set up at different angles in relation to the centre line of the plug 11 according to need.

With the present invention, a large technical advance is provided in this area which relates to test plugs in a disintegrateable/crushable material.

Claims

CLA I MS

1. Device for a plug for carrying out tests of a well, a pipe or the like, comprising a plug element made from a disintegrateable/crushable material arranged tobe crushed, characterised in that the device comprises an element arranged to move radially and provide a blow against the plug, by leading a release element in an axial direction, where said radial movement results in a crushing effect on the plug element.

2. Device according to claim 1 , characterised in that the element comprises one or more pegs that can move radially, and the release mechanism and the peg are built into the wall of a casing (12).

3. Device according to one of the preceding claims, characterised in that the casing that holds the plug comprises a boring for one or more axially moveable pistons that enable the peg or pegs to move radially.

4. Device according to one of the preceding claims, characterised in that the plug is made of glass, and comprises a "frosted glass" surface on the plug side surface in which the element is arranged to make the blow.

5. Device according to one of the preceding claims, characterised in that the one or several of the pistons are spring-loaded and move axially when released.

6. Device according to one of the preceding claims, characterised in that the pistons (3) move axially on release with the aid of the spring (1 ) and hit the peg (2) at the rear end, and through its wedge shape forces the peg (2) mainly horizontally into the plug (7), which is then crushed.

7. Device according to one of the preceding claims, characterised in that the pistons (3) and the springs (1 ) are fitted in a boring(s) (17) in a casing (12), which is mounted in a plug housing (11 ).

8. Device according to one of the preceding claims, characterised in that the pipe casing (12) comprises the release mechanism in the form of a valve (6), which when activated opens to let in fluid through the channel (5) and releases the piston (2) and spring (1 ) so that these move axially downwards and hit the peg (2), which is thereby pushed in the radial direction and crushes the plug.

9. Device according to one of the preceding claims, characterised in that the release mechanism reads pressure pulses in the pipe with the aid of mechanical, acoustic electrical, ultrasound or hydraulic reading, and opens the valve (6) when receiving the correct pulse signal.

10. Device according to one of the preceding claims, characterised in that a lower part of the piston (3) is cut at an angle/pointed to form a pin (40), and when this is pushed downwards the peg (2) is pushed radially inwards so that its point (42) ^< penetrates the plug element, whereby said axial movement is transferred into a radial movement.