FIELD OF THE INVENTION

The present invention relates to a method of plastically deforming an outer wellbore tubular with an expansion tool located within an inner wellbore tubular arranged in a central bore of the outer wellbore tubular.

BACKGROUND TO THE INVENTION

W02022078800A1 describes an inner tubular (an isolation joint) arranged within a surrounding tubular string (“outer tubular”). The inner tubular is either cemented within the surrounding string or an open annulus may extend between the inner tubular and the outer tubular. After activating a local expander tool from within the inner tubular, both the inner tubular and the surrounding outer tubular have undergone local radial expansion resulting in plastic deformation. In case the outer tubular is cemented in place, the local expansion causes affected zones in the surrounding cement layer, which can seal cavities and seepage paths in a similar manner as disclosed in e.g. US patent 10,794,158 and W02020016169A1.

In both cases described above, the annulus between the inner tubular and the outer tubular is tightly sealed off by the locally expanded part of the inner tubular.

WO2014148913 discloses a method for plugging a well. The annulus between the two pipe bodies is filled with viscous, precipitated drilling mud. Explosive charges detonated from within the inner pipe causes the diameter of the pipe bodies to extend. It takes quite some time for precipitated drilling mud to form. Moreover, after precipitation it is expected to be difficult to conventionally circulate the mud out of the well to surface. A perf and wash operation is described in WO2014148913 to remove the precipitated drilling mud from the annulus.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided a method of plastically deforming an outer wellbore tubular with an expansion tool located within an inner wellbore tubular arranged in a central bore of the outer wellbore tubular. The method comprises: - providing an outer wellbore tubular and an inner wellbore tubular arranged within a central bore of the outer wellbore tubular whereby an open annulus extends between the inner wellbore tubular and the outer wellbore tubular allowing passage of a fluid along a length direction of the outer tubular wellbore tubular;

- providing a dilatant material filling up at least a length interval of the open annulus;

- providing an energetic expander at a location within the inner wellbore tubular and within the length interval along which the open annulus is filled up with the dilatant material;

- detonating one or more explosive charges of the energetic expander at said location, thereby effectuating a local radial plastic deformation of the outer wellbore tubular whereby the dilatant material transmits a radial outward force from the inner wellbore tubular to the outer wellbore tubular; and

- subsequently disposing of the dilatant material from the length interval.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accordance with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.

Fig. 1 (not according to the invention) schematically shows a cross section of a first wellbore configuration before local expansion;

Fig. 2 (not according to the invention) schematically shows a cross section of the first wellbore configuration of Fig. 1 after local expansion;

Fig. 3 (not according to the invention) schematically shows a second wellbore configuration after local expansion;

Fig. 4 schematically shows a third wellbore configuration after local expansion illustrating an embodiment of the invention;

Fig. 5 schematically shows the third wellbore configuration of Fig. 4, after local expansion illustrating the embodiment of the invention;

Fig. 6 schematically shows the third wellbore configuration of Figs. 4 and 5, after local expansion and disposing of the dilatant material, illustrating the embodiment of the invention; and

Figs. 7a and 7b show graphs of pipe diameter (D) as function of axial location (E). DETAILED DESCRIPTION OF THE INVENTION

The person skilled in the art will readily understand that, while the detailed description of the invention will be illustrated making reference to one or more embodiments, each having specific combinations of features and measures, many of those features and measures can be equally or similarly applied independently in other embodiments or combinations.

The present invention relates to locally expanding downhole tubulars with a local expander device. Such a local expander device generally is held at one axial location (depth) within a downhole tubular (usually comprised in a string of downhole tubulars), while radially expanding an expandable section in the downhole tubular.

As described herein, it is presently proposed to plastically deform an outer wellbore tubular in which an inner tubular is arranged with an open annulus extending between the inner wellbore tubular and the outer wellbore tubular. Such a configuration is often encountered where the inner wellbore tubular is a production tubing which is provided uncemented within a casing string which could form the outer downhole tubular. The outer wellbore tubular is not necessarily the outer-most wellbore tubular: it can run inside yet another one or more other wellbore tubulars. The outer wellbore tubular itself is preferably cemented in place, whether against open formation rock or against a further surrounding wellbore tubular.

Drilling fluids such as drilling mud are commonly shear-thinning (“pseudoplastic”) fluids. The proposed method, in contrast, employs a dilatant material in the open annulus. A dilatant material, also known under the term “shear thickening material” or “shear thickening fluid” is one in which viscosity increases with rate of shear strain imposed on the material. Such dilatant material is a type of a non-Newtonian fluid, and the shear thickening behavior is usually not observed in pure materials but can occur in certain suspensions. Examples include com starch in water (“oobleck”), dispersed silica in polyethylene glycol, and fluids with generally high concentration of silicone polymer. While other examples may be found suitable, it is Applicant’s present preference to employ corn starch in water in wellbores in the Earth, for cost and environmental reasons.

When activating an energetic expander within the inner wellbore tubular, at a location where the surrounding annulus is filled with the dilatant material, a local radial plastic deformation of the outer wellbore tubular can be effectuated, as the dilatant material can undergo strain hardening due to the explosive expansion of the inner wellbore tubular and efficiently transmit a radial outward force from the inner wellbore tubular to the outer wellbore tubular.

Preferably, the radial displacement of the outer wellbore tubular is at least 50 % of the radial displacement of the inner wellbore tubular.

The dilatant material can subsequently be disposed from the annulus, e.g. by diluting it and/or removing it. Dilatant fluid can be circulated out conventionally. In some cases, the dilatant matter may break down or degrade over time. For example, com starch will break down under influence of bacteria. However which way, whether by circulating out or degradation, it is achieved that the annulus between the inner wellbore tubular and the outer wellbore tubular will be free, e.g. for passage of fluids. Also, the inner wellbore tubular is still free and can be pulled out of the wellbore at a later stage. This is an important difference with prior art method of W02022078800A1, in which either a solid cement annulus surrounds the inner wellbore tubular or in which the inner tubular had to be expanded into physical contact with the outer wellbore tubular thereby substantially restricting fluid flow capacity through the annulus and/or clenching the inner wellbore tubular stuck against the outer wellbore tubular.

When the outer wellbore tubular is cemented in place, the presently proposed method can be used to remediate integrity issues in the cement such as micro-annuli or other leak paths. The general principle of using local energetic expansion to densify and reset a cement sheath in an annulus has been disclosed in earlier publications, of which US patent publication No. 2021/0348473 Al (incorporated by reference) is an example. However, the present method allows to extend the applicability of this method to configurations wherein an uncemented inner wellbore tubular extends thought the cemented outer wellbore tubular.

Any suitable type of energetic expander device can be employed. Such devices may be run in any suitable manner, such as on wireline, slickline or coiled tubing. Specific tool designs of energetic expanders are disclosed in for example US Patents 11,015,410 and 11,002,097 and US patent publication No. 2022/0049566 Al. These tools employ shaped charges to direct an explosive pressure wave transversely to the tool axis. Each explosive unit includes an explosive material formed adjacent to a backing plate and includes an exterior surface facing and being exposed to the inner surface of the housing. An aperture extends along the axis from one backing plate to the other backing plate. An explosive detonator is positioned along the axis adjacent to, and externally of, the one backing plate. The first and second explosive units comprise a predetermined amount of explosive sufficient to expand, without puncturing, at least a portion of the wall of the tubular into a protrusion extending outward into an annulus adjacent the wall of the tubular. The force imparting section is activated by detonating the explosive charges. After detonation, the explosive charges generate an outwardly directed pressure wave over a full 360° radiation angle in a plane transverse to a longitudinal axis of the downhole tubular (and that of the local expander device) in the expandable section. This results in an applied radial strain on the isolation joint within the expandable section.

The explosive charges of e.g. US Pat. 11,002,097 are normally machined from steel parts and will break into smaller pieces post firing, leaving undesired debris behind in the wellbore. Such debris inside production wells may lead to blockages across downhole valves or flowline valves. To resolve this debris issue, it is proposed to manufacture the explosive housing and internal parts from dissolvable material. Such dissolvable material, which degrade downhole in interaction with a wellbore fluid, is commercially available for frac barriers and frac balls. Known dissolvable materials include dissolvable metals, such as Terv Alloy 3241 (Trademark). Suitable information may be available in one or more of US Patents 9,903,010; 10,150,713; and 9,757,796.

Figure 1 illustrates a first wellbore configurations, in which two wellbore tubulars are cemented in place. The annulus extending between the two wellbore tubulars is partially filled with cement 3, above which a fluid column 5 is present. The inner wellbore tubular 1 has sufficient cement 3 on the outside to cover an impermeable rock formation 6. The outer wellbore tubular 2 is installed above a source rock formation 7, that contains fluids under pressure. It is cemented in place with cement barrier 4. The fluids under pressure can escape via seepage 8 to surface, in case of a leaking cement barrier 4 around the outer wellbore tubular 2.

An energetic expansion tool 9, comprising one or more explosive charges, can then be conveyed in the inner wellbore tubular 1, e.g. via wireline 10, to location at a depth across the impermeable formation 6. After firing the expansion tool 9, involving detonating the explosive charges, the inner wellbore tubular 1 will be locally expanded at 11, whereby the cement 3 will transmit the expansion force to the outer wellbore tubular 2, which will then be expanded as well, as shown at 12. Expansion of the outer wellbore tubular 2, will stop the fluid migration 8 and create an interruption of any seepage at the affected zone 13 of impacted cement. In certain applications, such as for example illustrated in Fig 3, one or more uncemented wellbore tubular strings are present in the wellbore across the target expansion depth, i.e. at the impermeable formation 6. Fig. 3 illustrates that the top of cement 14 in this second wellbore configuration is located below the impermeable formation 6. The fluid column 5 is present above the cement top 14. Instead of top of cement, the fluid column 5 in the uncemented annulus may be above a production packer (not shown). Typically, this fluid may be a completion brine or degraded drilling fluid, and it generally has a low viscosity. The expansion tool 9 typically expands the inner wellbore tubular 1 (locally shown at 16) much more than the outer wellbore tubular 2, since the low viscosity fluid 15 in the fluid column 5 between the inner wellbore tubular 1 and outer wellbore tubular 2 will not transmit sufficient expansion force to push the outer casing 2 outward and plastically deform it as much as the inner wellbore tubular 2. Moreover, the explosive energy in the expansion tool 9 can be designed up to the forming limit of the inner wellbore tubular 1, which poses a “fundamental” limit on the ability to deform the outer wellbore tubular 2 if the aim is to preserve a certain tubular integrity of the inner wellbore tubular 1, for example to perform a subsequent through-tubing cementation effectively. Therefore, the seepage 8 may not be addressed adequately.

Conventionally, the inner wellbore tubular 1 will be removed from the wellbore by means of a cut and pulling operation, which involves a large surface unit such as a rig. Alternatively, cement can be over-displaced into the annulus, through tubular perforations, to enable double casing expansion similar to Fig. 2. However, if the expansion of both the inner wellbore tubular 1 and outer wellbore tubular 2 doesn’t resolve the seepage 8, then it might be very difficult to access the cement barrier 4 for remedial work.

This method currently proposed comprises a method to enable expansion of the outer wellbore tubular 2 in an uncemented condition whereby at the desired location of the expansion a dilatant fluid is provided (instead of, for example, the low viscosity fluid 15 of Fig. 3). One way to accomplish this, as illustrated in Fig. 4, is that the inner wellbore tubular 1 is perforated 18, allowing a circulation path from the bore of the inner wellbore tubular 1 to the annulus extending between the inner wellbore tubular 1 and the outer wellbore tubular 2. Subsequently, a slug of shear thickening (dilatant) fluid 17 is circulated down, and spotted across the impermeable formation 6. This should be done slowly, so as not to cause excessive shear hardening of the dilatant fluid 17 in the process. As schematically shown in Fig. 5, once the dilatant fluid 17 is in place, spanning a length interval at the desired location, the energetic expander tool 9 is subsequently activated to expand the inner wellbore tubular 11, whereby the shock wave will cause the shear thickening fluid 17 to temporarily solidify. The shear thickening fluid 17, in turn, transmits the expansion energy towards the outer wellbore tubular 2, thereby causing a permanent deformation 12, and sealing off fluid migration at the affected zone 13.

As illustrated in Fig. 6, the shear thickening fluid 17 can subsequently be disposed of. For instance, it may be circulated out to surface after the expansion operation, leaving a low viscosity fluid e.g., brine in the annulus at 19. The apex of the radial expansion of the outer wellbore tubular is indicated at 20 and the apex of the radial expansion of the inner wellbore tubular is indicated at 21.

Upon a certain annular monitoring period, verifying a good annular cement seal, the well may then for instance be abandoned by means of a through tubing cementation. In the event seepage 8 remains, the inner wellbore tubular 1 can be cut and pulled to surface for additional remediation work by conventional means such as section milling or perforate and squeeze in the outer wellbore tubular 2. This would be much more elaborate in case the annulus had been filled with cement.

Alternatively, the perforations 18 could patched, and the inner wellbore tubular 1 could be used as before the remediating operation. This may be the case if for example the inner wellbore tubular 1 is a production tubular which is not cemented in place but held in place with a production packer.

Instead of circulating the slug of shear thickening (dilatant) fluid 17 down into the wellbore, it is contemplated to employ an injection tool through which the shear thickening fluid 17 is injected from within the inner wellbore tubular 1 into the annulus. The injection tool may carry the shear thickening fluid 17 down in one or more cannisters from where the fluid can be carefully injected while whereby avoiding prohibitive amount of thickening. Injection may be effectuated after creating one or more perforations, similar to what is shown in for example WO2018115053A1. Alternatively, there are punch and inject tools which can create the perforation and inject the fluid in one integrated process step. Examples of such tools are illustrated in, for example: US Pat. 2,381,929; W02020229440A1; International application Nos: PCT/EP2022/081438, PCT/EP2022/081439, and PCT/EP2022/081440; and W02021080434A1. Alternative tools may be available. In another alternative to said circulating, the shear thickening fluid 17 maybe introduced via a sliding door mandrel or a side pocked mandrel, provided in the inner wellbore tubular 1.

Shear thickening fluid may also enable smaller expansion charge tools when surrounded or submersed in the dilatant fluid. In low viscous fluids the radial expansion energy dissipates in longitudinal direction, whereas a dilatant fluid will stop the longitudinal shock wave and divert it into a radial direction, resulting in a higher, downhole, expansion energy efficiency per gram weight of explosive.

In respect of any of the embodiments described hereinabove, in operation, prior to running the local expander device, a casing collar locator (CCL) tool may be run in any of the embodiments described herein. The CCL may form part of a drift tool string, and can be utilized to verify the precise location of the isolation joint. This reduces the risk of landing the local expander device on a casing restriction which is not the intended mating support, and locally expanding the wellbore tubular at a wrong depth (i.e. outside of the intended expandable section). The wall thickness variation profile (in axial direction) of the isolation joint described herein can be identified on a CCL-log with high degree of certainty.

Laboratory tests have been performed to demonstrate the effect of a dilatant material in the annulus compared to pseudoplastic (shear-thinning) material. The tests were performed using a structure consisting of a 7” L80 middle tube (outer diameter 177.8 mm; wall thickness 9.2 mm) cemented coaxially in a 9-5/8” L80 outer tube (outer diameter 244.5 mm; wall thickness 12.0 mm) with a Portland class-G cement. A 4-1/2” (13Cr)L8O inner tube (outer diameter 114.3 mm; wall thickness 6.9 mm) was concentrically arranged within the middle tube. In one section, the annulus between the inner tube and the middle tube was filled with a mixture of Xanthan gum (mix ratio of 10 gram per liter) and water and in another section the annulus between the inner tube and the middle tube was filled with a mixture of com starch and water (mix ratio of 1.14 kg per liter). Xanthan gum was employed in the present tests to mimic non-Newtonian aspects of drilling mud. Xanthan gum is a known component of so-called viscous pills, and it imparts a pseudoplastic property to the fluid. Corn starch imparts dilatant (shear-thickening) behavior on the fluid. The structure was submerged in a water basin and each section was expanded using a 1- 3/8” dual end firing explosive column as described in e.g. U.S. patent No. 11,015,410 as the energetic expander. It was charged with 204 grams of HMX in a 152-mm long explosive column in all cases.

After the expansion, the (average) outer diameter and wall thickness of the outer tube were measured, as a function of axial location L on the tube relative to the midpoint of the explosive column. The wall thickness was measured ultrasonically. By subtraction, the inner diameter was inferred. Both the inner diameter and outer diameter are plotted in Fig. 7a with diameter D on the vertical axis and axial location L on the horizonal axis.

Table 1: Legend Fig. 7a (outer tubular)

It can clearly be seen that the outer tubular has expanded significantly more with the mixture of com starch and water in the annulus, than it did with the mixture of Xanthan and water in the annulus, for the same amount of explosive charge.

Furthermore, the inner tube was pulled out of the structure, and the (average) outer diameter and wall thickness were measured as a function of axial location. The inner diameter and outer diameter are plotted in Fig. 7b with diameter D on the vertical axis and axial location L on the horizonal axis.

Table 2: Legend Fig. 7b (inner tubular)

Interestingly, the inner tube was expanded less in the case of the mixture of com starch and water in the annulus compared to the case of the mixture of Xanthan and water in the annulus. This confirms that the dilatant fluid has helped to transmit the explosive energy more effectively to the outer tubular, to ultimately cause more plastic deformation in the outer tubular. It may also be concluded that even more plastic deformation of the outer tubular could potentially have been achieved, by increasing the amount of explosive charge in the energetic expander, as curves 25 -i and 25-o in Fig. 7b show that the rupture limit of the inner tubular had not been reached.

Table 3 lists the ratio between the radial expansion of the outer tubular and the radial expansion of the inner tubular. Radial expansion is the absolute increase in diameter at the apex 20 of the outer tubular, and at the apex 21 of the inner tubular, when compared to the original outer diameter of the tubular in question.

Table 3: ratio of radial expansion

It can be inferred from Table 3 that the ratio of the radial expansion of the outer tubular over the radial expansion of the inner tubular in the experiment with corn starch in water exceeds 0.50 (50%), while in the experiment with Xanthan and water it was well below 0.50. This further demonstrates the effectiveness of the explosive energy to reach and deform the outer tubular is enhanced by using the dilatant fluid in the annulus.

The test was repeated with the same structure as described above, whereby the annulus between the inner tube and the middle tube was filled with water instead of Xanthan gum or corn starch. In this case, as shown by the interruption of curves 27-o and 27 -i in the interval between L « -280 and L « +160, the inner tube had ruptured. As shown by comparison of curves 24-o and 26-o (and/or 24-i and 26-i), the outer tube expansion is about the same as with the Xanthan mixture.

The person skilled in the art will understand that the present invention can be carried out in many various ways without departing from the scope of the appended claims.