GB2139670A - Bore hole packers - Google Patents

Abstract

A bore hole packer has an expandable packing element 6 located between two sleeves 7 and 8 and another sleeve 3 is disposed between the packing element 6 and a bore hole casing 1. A bore 17 allows pressure to be exerted from the inside of the casing 1 onto the sleeve 3 between the packing element 6 and casing 1 which moves the sleeve so that a bore 13 in the sleeve is aligned with a non- return valve 9 in the casing and the packing element 6 may be inflated via the non-return valve 9. The packing element is inflated against the side of the bore hole to separate the zones above and below. This can be useful in for example oil wells in which certain sensitive areas must be sealed off. <IMAGE>

Description

SPECIFICATION Bore hole packers The invention relates to bore hole packer arrangements, particularly for separation of zones in a well bore.

A packer arrangement comprising a tubular member serving as mandrel for an expandable packing element and first and second sleeves tightly fixed to the peripheries of the packing element, wherein the first sleeve is sealed and movable in respect of and the second sleeve is fixed to the tubular member, is well known in the prior art and is described in e.g. US-PS 3,776,308 or in the "Composite Catalog of Oilfield Equipment and Services", 34th Revision 1980-81, Volume 3, pg. 4722-4723 or in USSR Inventor's Certificate Nr.

327,316. The packer arrangments are used to stop interzonal communication outside the casing, i.e. in the annular space between the casing and the bore hole outside the casing.

Thus, selected portions in this annular space can be filled with a medium such as cement.

The bore hole often connects zones of different pressure and/or containing different phases such as mud, liquid, gas, rock etc.

Cement between the casing and bore hole can be damaged by perforating, acidizing and fracturing without separation of zones therein.

The known packers as described hereinabove are an integral part of the casing and are designed to provide a positive seal between the outer surface of the casing and the open hole well bore. The expandable packing element can be inflated by mud, water, pressurized gas or any agent normally available. The inflation agent is retained under pressure in the packing element in the course of cementing outside the casing while the pressure inside the casing is blown off.. For this, a quite complicated series of valves is used.

In the packer known from the above the catalogue, there are two double seal check valves and one shut-off valve. Thus, the inflating agent enters the packing element through a series of three valves. The first difficulty with the known solutions arises from the use of such a sophisticated valve assembly and from the sensitivity to sanding up or blocking up of the packer.

A valve arrangment is actuated in the known solutions by a cement wiper plug following the cement column which is forced by this plug into the annular space between the outer surface of the casing and the hole well bore. The plug when going down removes a break-off rod projecting from the casing in the way of motion of the plug and connected to the shut-off valve Thus the plug actuates the shut-off valve and the pressure applied to the casing inflates the packing element through a series of valves and the packing element will be pressed against the inner surface of the well bore.

With this, the spaces outside the casing, below and above the packer are separated from each other. Thus, upward motion of the cement in the annular space is blocked, too.

This means that the amount of cement in the annular space at the time of removing the breakoff by the plug must be enough to do all of the necessary cementing. For solving this problem, the use of delaying equipment was proposed which enlarged the complexity and sensitivity to damage of the valve arrangement.

In the prior art, when the plug comes to a seat in the casing, the pressure is released from the casing, theshut-off valve locks and the check valves close, if they function properly. The pressure in the packing element must remain stable at least for the time of hardening the cement.

However, the most significant difficulty in using the known packers is in the fact that in one casing only a single packer can be used.

If there were two of them, the first would be activated when the plug passes by and the annular space between the outer surface of the casing and the well bore would be blocked, more cement could not be pressed into it. The plug could not come to its seat at the bottom of the casing and the second packer could not be actuated at all.

A first and principal object of this invention is to obviate the deficiencies of the known solutions. A further object is to create a packer arrangement in which the valve assembly is less complicated and thus, in which its function is more reliable and its fabrication is cheaper, and in which more than one packer can be used with one casing.

The basic idea of our invention is in that the valve assembly should be simplified and it should be controlled by the pressure in the casing rather than by the motion of a mechanical member such as a cement wiper plug.

According to the invention, we propose a bore hole packer for separation of zones outside a casing in a bore hole, comprising an expandable packing element, a casing to act as a mandrel in inflation of the expandable packing element, a first sleeve having first and second portions, the first portion disposed between the casing and a collar mounted on and immovable with respect to the casing and the second portion disposed between the casing and the packing element, wherein the packing element is disposed between a second sleeve, which is immovable on the casing and located at the end of the packing element further from the collar, and a third sleeve at the other end of the packing element and movable on the first sleeve, a non-return valve in the casing connecting the inside of the casing and the first sleeve adjacent the packing element, a first bore in the casing beyond the first portion of the first sleeve in its initial position and a second bore in the first sleeve alignable with the non-return valve, wherein on exertion of sufficient pressure via the first bore, the first sleeve is movable towards the second sleeve to align the second bore and the non-return valve whereupon the packing element may be inflated via the non-return valve.

A collar is tightly fixed to the casing for being in the annular space between the outer surface of the casing and the well bore and a sleeve plug is provided which is sealed against and slides on the outer surface of the casing from a starting position to a lower position and, further to a final position. The sleeve plug has a thicker upper part and thinner lower part. The upper part is arranged between the outer surface of the casing and the inner surface of the collar and is se sealed against both of them. The lower part is slidingly arranged at least partially between the outer surface of the casing and the inner surface of the packing element and is sealed against both of them. The first sleeve connected to the packing element is sealed against and slides on the sleeve plug.Serving as valve assembly, a non-return valve is provided in the casing between the inside and the outside of the casing at the packing element. Furthermore, two bores are provided, the first one in the lower portion of the sleeve plug connecting the non-return valve and the space between the packing element and sleeve plug in the lower position of the sleeve plug, the second bore is made in the casing above the upper portion of the sleeve plug in its starting position. The tubular member can be in the form of a casing or lining or similar.

The non-return valve provides a flow path towards the sleeve plug.

In a preferred embodiment, the non-return valve has a valve body and a perforated plate acting as a filter, the valve body rests on the perforated plate and is made of resilient material.

A shear pin can be provided which fixes the sleeve plug in respect of the casing in the starting position of the sleeve plug.

In another embodiment, a blocking device can be provided in the upper part of the sleeve plug and in the collar for fixing the sleeve plug in its final position. This invention can be used with fluid in any type of bore hole but is partiuclarly useful in oil wells.

Further details of our invention will be described in connection with a preferred embodiment by way of example with reference to the drawings in which: Figure 1 shows a schematic cross section of half the packer arrangement according to this invention, in the starting position of the sleeve plug; Figure 2 is the same as Figure 1 but with the sleeve pluck in a lower position; and Figure 3 is the same as Figure 1 but with the sleeve plug in the final position.

In Figure 1, a portion of the cross section of an open hole bore well is shown, in which casing 1 is disposed. The portion of the casing 1 shown in the figure serves as a support for a packing arrangement for the separation of zones outside the casing 1 in the well bore. On the casing 1 a collar 2 is tightly fixed forming an annular pocket-like space around the outer surface of the casing 1.

Under the collar 2 and partly in the pocketlike space, a sleeve 3 is provided which is sealed against and slides on the outer surface of the casing 1. The sleeve 3 has a thicker upper part 3a integral with a thinner lower part 3b. The upper part 3a has an upper end surface A which has a larger area than a surface C at the step between upper part 3a and lower part 3b. The lower part 3b has an end surface B too, which is smaller than surface C. Surfaces A, B and C, respectively, serve as work surfaces of the sleeve plug 3.

As it is stated above, the upper part 3a is slidingly disposed on the outside of the casing and the collar 2 and is sealed with seals 12 against both of them. The lower part 3b also slides on and is sealed with seals 14 against the casing 1.

Around the casing 1, an expandable packing element 6 is arranged, on the ends of which a first sleeve 7 and a second sleeve 8 are tightly fixed. The packing element 6 can be made of any suitable material having the required strength, resilience (expandability) and sealing capability on the outer surface.

The material can be a kind of rubber reinforced with e.g. steel cord. Into the rubber, a steel rib can be vulcanized as reinforcement too. However, the rubber can be replaced with any suitable plastics, as well. Sleeves 7 and 8 are vulcanized or otherwise tightly adhered to the packing element.

The first sleeve 7 slides on and is sealed with seal 15 against the outer surface of lower part 3b of sleeve plug 3. The second sleeve 8 is firmly fixed to and immovable on the outer surface of casing 1.

In the casing 1, a non-return valve 9 is provided which connects the inside of the casing 1 and the packing element 6 in Figure 1. The non-return valve 9 has a valve tapered bore and a valve body 10 within the bore as well as a perforated plate 11 in the outer surface of the casing 1. The valve body 10 is made of a resilient material and sits adjacent perforated plate 11 which, in turn, serves as a filter. The end of the valve body 10 sealingly fits in the tapered bore of the non-return valve 9. Thus, a flow path is provided directed towards sleeve 3.

In the sleeve 3, a bore 1 3 is made which, in the starting position as shown in Figure 1, is above the non-return valve 9 and, prefera bly, above seals 14.

Furthermore, in the casing 1, another bore 1 7 is made above the upper end surface A of sleeve plug 3 in its starting position as shown in Figure 1. It connects the inside of casing 1 and the pocket-like space above surface A of collar 2.

The sleeve 3 is held in its starting position in the casing 1 by a shear pin 5.

In Figure 1, a stop device 4 in sleeve 3 with annular slot 4a in the inner surface of collar 2 is shown , too, the function of which will be discussed later.

For the tight connection of casing 1 and collar 2, a seal 1 6 is provided between them.

To described the operation of our invention, reference is also made to Figures 2 and 3.

When cementing the space between the outside of the casing 1 and the well bore, cement is forced upwards in this space by a cement wiper plug (not shown) moving down in the inside of and being sealed against the inner surface of the casing 1. To move the cement wiper plug down, pressure is applied in the casing 1 above the plug. When the wiper plug comes to a seat at the bottom of the casing and all of the cement is forced out of the casing 1 and into the space to be cemented, the pressure within the casing will increase. This pressure is constantly communicated via bore 1 7 in Figure 1 into the space above sleeve 3 and applies a downward force on the end surface A. On the smaller surface C, a smaller pressure of the cement will cause a much smaller upwardly directed force. On end surface B, there is no pressure at all.

When the pressure inside the casing 1 and, thus, the downward force at surface A is great enough, the pin 5 will be sheared and the sleeve 3 starts a downwards motion. In the course of this, it slides on the outer surface of casing 1, on the inner surface of collar 2 and the first sleeve 7 slides on its outer surface.

Finally, sleeve 3 reaches its lower position wherein bore 1 3 is in alignment with the bore of the non-return valve 9.

In Figure 2, the lower position of sleeve plug 3 and the process of setting the packer i.e. inflation of packing element 6 are shown The pressure inside the casing 1 will open the non-return valve 9 by moving the valve body 10. Then, the pressurized agent, e.g. ffluid in the inside of casing 1 enters the space between sleeve 3 and packing element 6 through the opened non-return valve 9 and further through bore 1 3. As it is clearly shown in the figure, the outer resilient surface of packing element 6 will be firmly pressed against the surface of the well bore.

After the inflation has come to an end, the pressure inside the casing 1 will reach a minimum. The pressure in the space between sleeve 3 and packing element 6 will be greater than in the inside of casing 1 which, through bore 13, immediately shuts off the non-return valve 9 and exerts at the same time an upwardly directed force on end surface B. As a result of this, the sleeve plug 3 will move upwards and bore 1 3 moves away from the non-return valve 9 and seals 1 4. At the end of this motion, end surface A will impact on collar 2 and blocking device 4 will snap into annular slot 4a.

This is the final position of sleeve plug 3, which is shown in Figure 3. The pressure within the packing element 6 cannot escape since the only exit through bore 1 3 and valve 9 is blocked twice: by sealing assembly 14 and non-return valve 9. Now, the zones above and below the inflated packing element are sealed off.

It will now be clearly apparent that the packer according to this invention is much more simple in construction and will be more reliable than the previously knownpackers.

Claims (6)

1. A bore hole packer for separation of zones outside a casing in a bore hole, comprising an expandable packing element, a casing to act as a mandrel in inflation of the expandable packing element, a first sleeve having first and second portions, the first portion disposed between the casing and a collar mounted on and immovable with respect to the casing and the second portion disposed between the casing and the packing element, wherein the packing element is disposed between a second sleeve, which is immovable on the casing and located at the end of the packing element further from the collar, and a third sleeve at the other end of the packing element and movable on the first sleeve, a non-return valve in the casing connecting the inside of the casing and the first sleeve adjacent the packing element, a first bore in the casing beyond the first portion of the first sleeve in its initial position and a second bore in the first sleeve alignable with the non-return valve, wherein on exertion of sufficient pressure via the first bore, the first sleeve is movable towards the second sleeve to align the second bore and the non-return valve whereupon the packing element may be inflated via the non-return valve.

2. A packer according to claim 1, wherein the non-return valve provides a flow path directed towards the first sleeve.

3. A packer according to claim 1 or 2, wherein the non-return valve has a valve body made of resilient material and sits adjacent a perforated filter plate.

4. A packer according to claims 1, 2 or 3, wherein a frangible pin is fixed between the casing and the first sleeve in its initial position.

5. A packer according to any one of claims 1 to 4, wherein a stop is provided in the first portion of the first sleeve and in the collar for securing the first sleeve in a final position.

6. A bore hole packer constructed and arranged substantially as herein described with reference to any of the Figures of the drawings.