WELLBORE PASSAGE

FIELD OF THE INVENTION

The invention relates to a method and system for cladding an inner surface of an underground wellbore passage. The invention further relates to a sleeve for cladding an inner surface of an underground wellbore passage .

BACKGROUND

US 2011/0297400 discloses an inflatable packer for use in wellbores to isolate specific wellbore regions. The inflatable packer has an expandable bladder which is expanded, e.g. inflated, into sealing engagement with a surrounding surface inside the wellbore (such as the wellbore wall surface) . The expandable bladder is pre-manufactured with a radially enlarged section relative to the axial ends of the expandable bladder when the bladder is in relaxed state. The radially enlarged section offers a reduction in required expansion ratio that is required to transition the packer into sealing engagement with the surrounding surface by inflating. Inflating can be accomplished by excersising an axial force along the packer.

The packer of US 2011/0297400 is not suitable for some applications, as it requires continuous energizing to maintain the packer into sealing engagement with the surrounding surface .

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention there is provided a method for cladding an inner surface of an underground wellbore passage, the method comprising :

- providing an elastic sleeve comprising a stretching device within the sleeve which stretching device is connected to opposite ends of the sleeve;

- inducing the stretching device to stretch the sleeve in a longitudinal direction, thereby reducing its largest outer width such that it is less than the smallest width of the inner surface;

- lowering the stretching device and the stretched sleeve into the wellbore passage;

- releasing the sleeve from the stretching device thereby enlarging the outer width of the sleeve and cladding the sleeve against the inner surface.

In accordance with another aspect of the invention there is furthermore provided an elastic sleeve for cladding a inner surface of an underground wellbore passage, the sleeve having a larger outer width than the width of the inner surface and being:

- connectable to a stretching device within the sleeve and to be longitudinally stretched by the stretching device thereby reducing its outer width such that it is less than the width of the inner surface; and

- releasable from the stretching device after lowering with the stretching device in stretched condition into the wellbore passage, thereby enlarging its outer width and cladding the sleeve against the inner surface.

The underground wellbore passage may be formed by the wellbore itself, or by a wellbore tubular arranged within the wellbore.

In accordance with still another aspect of the invention, there is provided a system for cladding an inner surface of an underground wellbore passage, comprising an elastic sleeve as defined above and a stretching device arranged within the sleeve, which stretching device is releasably connected to opposite ends of the sleeve. These and other features, embodiments and

advantages of the method and system according to the invention are described in the accompanying claims, abstract and the following detailed description of non- limiting embodiments depicted in the accompanying drawings, in which description reference numerals are used which refer to corresponding reference numerals that are depicted in the drawings .

Objects and other features depicted in the figures and/or described in this specification, abstract and/or claims may be combined in different ways by a person skilled in the art .

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically shows a longitudinal section A-A through a system for cladding an underground wellbore passage;

Fig. 2 schematically shows a top view of the system of Fig. 1 in the longitudinal direction;

Fig. 3 schematically shows a perspective view of the system of Fig. 1;

Fig. 4 schematically shows a longigudinal section of a wellbore after cladding with the system of Fig. 1; and

Fig. 5 schematically shows the same view on the wellbore after inserting a cement slurry.

DETAILED DESCRIPTION OF THE DEPICTED EMBODIMENTS

An inner surface of an underground wellbore passage (which can be the wellbore itself or a wellbore tubular) is cladded by an elastic sleeve, which is placed by:

- lowering the elastic sleeve into the wellbore which sleeve is releasably connected to a stretching device arranged within the sleeve and stretched by the stretching device in longitudinal direction thereby reducing its largest outer width such that it is less than the smallest width of the inner surface

surrounding the elastic sleeve; and

- releasing the sleeve from the stretching device thereby enlarging the outer width of the sleeve and cladding the sleeve against the inner surface.

When detached from the stretching device, the elastic sleeve has an outer width that exceeds the inner width of the inner surface of the wellbore passage in a location where cladding is desired.

Figures 1, 2 and 3 show an elastic sleeve 1, as example, which has end sections 1A, IB in which tensioning rods 2 are embedded at regular

circumferential intervals. The tensioning rods 2 are configured to be coupled to a stretching device 4. The sleeve 1 is stretchable by longitudinal expansion of the stretching device.

In the shown embodiment, the stretching device 4 comprises two flanges 7,8 longigudinally spaced from each other and between which the sleeve can be

configured. These flanges 7,8 are provided with longitudinal slots 5 distributed around the

circumference and radially accessible. The tensioning rods 2 are configured with heads 6 at their distal ends relative to the sleeve 1. The tensioning rods 2 are held in the longitudinal slots 5 with the heads 6 preventing slipping of the tensioning rods 2 through the slots in longitudinal direction. The flanges 7,8 are longitudinally moved away from each other to stretch the sleeve 1 by creating longitudinal tension.

It can also be seen that the outer diameter of the flanges is smaller than the outer diameter of a middle section of the sleeve. When the tension rods 2 are inserted in the slots 5, the tension rods 2 are preferably pushed radially inward whereby elastically deforming the sleeve beween the middle section of the sleeve and the end sections 1A and IB. This way, when the stretching device 4 is released, for instance by reducing the longitudinal spacing between the flanges 7 and 8, the elastic force which is directed radially outward will cause the tensioning rods 2 to

automatically slide out of the slots 5 in radial direction. This way, the stretching device 4 may automatically detach from the sleeve 1 upon releasing the longitudinal tension.

In stretched state the tension rods 2 may be kept in place by virtue of friction between the heads 6 and the flanges 7, 8. Suitably, some recesses may be provided on the flanges 7, 8 for retaining the heads 6.

About halfway between each pair of tensioning rods 2, a V-shaped groove 3 may be present to mitigate formation of ridges in between the rods 2 during stretching of the sleeve 1. A V-shaped groove may be arranged in each interval of each end section.

The sleeve may comprise an elastic elastomer and a swelling agent that induces the elastomer to swell upon contact with water and/or another wellbore fluid. The swelling agent may be a water absorbing agent such as a super absorbent polymer or a hygroscopic salt which is dispersed in the elastic elastomer as an array of finely divided solid particles. For example, the sleeve 1 may be made of a rubber or other elastomeric material and comprise an additive that swells upon contact with water or another well fluid as described in Patent

Application Publications US 2007/056735 Al and/or US 2016/0040038 Al (both incorporated herein by reference) to generate a self-healing elastomer lining. An objective of the use of a self-healing elastomer sleeve 1 is to seal any micro-annuli and/or other leak paths on a cement casing interface directly after placing a cement plug inside the steel casing, liner or pipe. Any leak paths that may subsequently occur during the life of a well, e.g. induced by temperature or pressure changes, will be restored by the self-healing

properties of the elastomer sleeve 1. The elastomer sleeve 1 may swell in the presence of oil, water, brine and/or water condensed from an wet natural gas phase.

Before running into a wellbore the elastomeric sleeve 1 according to the invention is longitudinally stretched by a mechanical stretching tool 4 that pulls the opposite sets of rods 2 in longitudinal direction away from each other. The increase in length of the sleeve 1 causes a significant decrease in its Outer

Diameter (OD) . The stretched elastomer sleeve 1 can be Run Into Hole (RIH) to the desired downhole location within the wellbore. At the required downhole location the tension is released by longitudinal contraction of the stretching tool 4, which reduces the distance between the opposite sets of rods 2 thereby inducing the elastomer sleeve 1 to radially re-expand and regain its original length and Outer Diameter (OD), thereby creating a clad on the inner surface of the surrounding casing, liner, pipe or the formation.

As the tension is released the elastomer sleeve 1 detaches from the stretching device 4, after which the stretching device 4 may be withdrawn from the elastomer sleeve 1 and optionally retrieved from the wellbore 10 as shown in Fig. 4. The elastomer sleeve 1 stays behind in the wellbore.

The sleeve may be cladded against the inner surface of an uncased wellbore section or of a well casing, liner or other well tubular. The sleeve may suitably be configured to swell upon contact with water and/or another wellbore fluid.

The wellbore 10 may be a wellbore of an abandoned

011 and/or gas production well and after cladding the sleeve 1 against the inner surface 8, a cement slurry

12 may be inserted into the sleeve 1 and allowed to harden to plug the wellbore. This is schematically illustrated in Fig. 5. The sleeve 1 may be induced to swell and thereby seal any micro-annuli between the cement plug and the inner surface.

The self-healing elastomer sleeve 1 allows the use of ordinary (low cost) Portland class G cement slurries to provide long-term zonal-isolation. Other types of cement or well bore plugging materials, for example bentonite, barite or resins, may also be used.

Application of the self-healing elastomer sleeve 1 mitigates use of complex and expensive cement slurries comprising cement expansion additives to enhance zonal isolation. Known complex expanding cement slurries still don't give a 100% seal in all circumstances neither do they have self-healing properties.

Experiments showed that the sealing performance of the self-cladding sleeve 1 in combination with a simple and cheap Portland class G is superior to known complex and expansive cement systems as measured in the Wells R&D

Full scale Plugging and Abandonment (P&A) testing setup described in the Example provided below.

Recent field data show that a number of wells after placement of abandonment plugs have pressure build up at surface. In general this problem is attributed to the failure of cement due to either poor cement job during the primary cement job or generation of micro annuli during the curing or life time of a well. Micro annuli can be formed during curing of the cement (shrinkage) or due temperature, pressure cycles in a well. This may result in de-bonding of the cement from the casing. The current invention provides a self- healing sleeve 1 that adequately closes any micro annuli between the cement and the casing.

EXAMPLE

An experiment has been performed by stretching a tubular sleeve 1 with an initial Outer Diameter of 15 cm up to 60%, which generated a significant width decrease that matched calculations. The stretched sleeve 1 was then inserted into a full size Plugging & Abandonment (P&A) testing pipe with an Internal

Diameter of 15 cm (6 inch) . The stretching tool was subsequently retracted such that the sleeve 1 was also retracted and induced to regain its original diameter. A zonal-isolation test was performed on the sample. Sealing was proven after filling the interior of the sleeve 1 with a conventional Portland class G cement up to a pressure differential of 20 bar dP using nitrogen. At 30 bar dP a leak was initiated, which leak was cured due to the self-healing effect of the sleeve 1.

It will be understood that the method, system and/or any products according to present invention are well adapted to attain the ends and advantages

mentioned as well as those that are inherent therein.

The particular embodiments disclosed above are illustrative only, as the present invention may be modified, combined and/or practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein.

Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined and/or modified and all such

variations are considered within the scope of the present invention as defined in the accompanying claims .

While any methods, systems and/or products

embodying the invention are described in terms of "comprising," "containing," or "including" various described features and/or steps, they can also "consist essentially of" or "consist of" the various described features and steps.

All numbers and ranges disclosed above may vary by some amount . Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is

specifically disclosed. In particular, every range of values (of the form, "from about a to about b," or, equivalently, "from approximately a to b," or,

equivalently, "from approximately a-b") disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values .

Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.

Moreover, the indefinite articles "a" or "an", as used in the claims, are defined herein to mean one or more than one of the element that it introduces .

If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be cited herein by reference, the definitions that are consistent with this

specification should be adopted.