T 1833/17 09-12-2020

1. Applicable provisions of the EPC

1.1 The patent is based on an International application which was filed under the PCT on 12 July 2005, and was still pending at the time of entry into force of the revised EPC (EPC 2000) on 13 December 2007.

1.2 According to Articles 1(1) and 6, first sentence of the Decision of the Administrative Council of 28 June 2001 on the transitional provisions under Article 7 of the Act revising the EPC of 29 November 2000 (Special edition No. 4, OJ EPO 2007, 217), Articles 54(1)(2), 56, 84 and 100 EPC 1973 as well as Article 123 EPC (2000) apply.

2.

3. Withdrawal of the opposition

3.1 The withdrawal of the opposition means that the opponent ceased to be party to the proceedings in respect of the substantive issues, but it has no direct procedural consequences for the appeal proceedings since the opponent was the respondent and the contested patent was revoked by the appealed decision (see e.g. Case Law of the Boards of Appeal of the EPO, 2019, III.Q.3.3).

3.2 In the context of the patent proprietor's appeal, the Board can take into account the facts, arguments and evidence submitted by the opponent prior to the withdrawal of the opposition, when examining the correctness of the decision under appeal.

4. Admissibility of the appellant's request

4.1 The appellant filed its present request for the first time in response to the Board communication pursuant to Rule 100(2) EPC dated 30 April 2020.

4.2 Claims 1 and 3 differ from claims 1 and 3 of the third auxiliary request filed with the statement of grounds of appeal only in that the text "the or each space" has been amended to refer to "the space (16)".

4.3 These amendments were filed in direct reaction to the objection of lack of clarity (Article 84 EPC 1973), which was raised for the first time by the Board in this first communication pursuant to Rule 100(2) EPC (point 13.2). They clearly overcome all outstanding objections without introducing new issues. The Board thus sees no reason to disregard this request (Article 13(1) and (2) RPBA 2020).

4.4 The claims of the third auxiliary request filed with the statement of grounds of appeal differ from those of the third auxiliary request filed with letter dated 10 February 2017 in that dependent claim 4 has been deleted and the subsequent dependent claims have been renumbered accordingly. It can be inferred from the file that the appellant had already made these amendments in the oral proceedings before the opposition division (see decision under appeal, point 12 of the reasons; minutes of the oral proceedings, page 2). Therefore, the third auxiliary request filed with the statement of grounds of appeal corresponds to the third auxiliary request on which the appealed decision was based and thus they had to be considered in the appeal proceedings (Article 12(4) RPBA 2007).

5. Amendments to the claims

5.1 The Board shares the view of the opposition division that the amendments to the claims meet the requirements of Article 123(2) and (3) EPC (see decision under appeal, point 16 of the reasons).

5.2 The Board is also satisfied that the amendments do not introduce a lack of clarity (Article 84 EPC 1973).

6. Claim construction

6.1 Before turning to the objections of lack of novelty and lack of inventive step it is necessary to construe claim 1. In particular, the appellant disputes how the opposition division interpreted the terms "device" and "space" of claim 1.

6.2 Claim 1 is directed to a well system comprising, among others, a device for expanding into a space in a horizontal borehole, and a space at least partly defined by a cast material disposed radially between and in contact with the borehole and the device.

In the claim, the device is defined in terms of structural features as well as functional features specifying how the device expands into the space. The skilled person reading claim 1 may thus recognise that it defines a device intended for use in a well, or borehole, in which a space may eventually be formed after casting. In this respect, the skilled person knows that there is a large degree of chance that determines whether or not such a space will be formed in practice.

However, since claim 1 further requires that the well system comprises the space formed in the cast material and that this space has specific properties, the skilled person is left in doubt as to how these further features are to be construed in the context of the claim. This introduces an ambiguity as to the definition of the claimed subject-matter.

The skilled person would try to resolve this ambiguity by using the description of the patent. In doing so they would understand that claim 1 is not directed to the device per se, but rather to the well system comprising the borehole, the space formed in the cast material after casting, and the device expanded into the space. Thus, in the context of claim 1, the functional features characterising the device must be construed as "product-by-process" features describing the process of sealing the incompletely cemented annulus. In a nutshell, the subject-matter of claim 1 is essentially the product obtained directly by the process defined in claim 3.

The Board notes that the ambiguity mentioned above was already present in claim 1 as granted and thus it cannot give rise to an objection of lack of clarity under Article 84 EPC 1973 (see decision G 3/14, OJ 2015, A102).

6.3 "Device"

The opposition division based its decision on the argument that, in the context of claim 1, the "device" could and indeed should be understood as comprising the "sleeve" as well as the "pipe" defined in the claim.

The Board shares the appellant's view that this argument is not persuasive. Claim 1 requires that "the device comprises an annular sleeve disposed on the pipe in the borehole". When reading this feature in the context of the claim, it is apparent that the device comprises the sleeve, but not the pipe (see e.g. the wording "a device for sealing a void ... said void being in the form of an annulus between the outer surface of a tubular element which is a pipe and the borehole wall").

6.4 "Space"

6.4.1 Claim 1 requires that the device be adapted "for expanding into a space in a horizontal borehole, ... said space not being filled with the cast material such that the space is at least partly defined by the cast material disposed radially between and in contact with the borehole and the device", and that "the sleeve is made of an expandable material and is capable of swelling and extending from a retracted state to an expanded state in response to contact with a fluid in the well system, wherein the contact is with a fluid present in the or each space or by diffusion of the fluid present in the or each space into openings in the expandable material, the expandable material being arranged to expand into the space which is not filled with cast material".

6.4.2 Based on the above interpretation of the subject-matter of claim 1 and the term "device", these features imply among others that, after cast material has been filled into the annulus between the pipe and the borehole wall and then allowed to cure,

- the cast material is disposed radially between the device and the borehole wall,

- the cast material contacts the device,

- due to incomplete filling of the annulus with the cast material, a space not filled with cast material is at least partly defined by the cast material placed in the annulus,

- the device and its sleeve of expandable material expand into this space, and

- the sleeve has swelled and extended from a retracted state to an expanded state on contact with a fluid present in the space, or by diffusion of this fluid into the sleeve.

6.4.3 For the sake of completeness, the Board notes that this understanding is confirmed by the teaching in the patent (see e.g. space in form of channel 16 in Figures 1 and 2, and fluid 14 in annulus 10 in Figure 3).

7. Novelty

7.1 The Board is satisfied that the subject-matter of claims 1 and 3 is new in the sense of Article 54(1)(2) EPC 1973 over the cited prior art documents, in particular D4, D3, D5 and D6.

7.2 Document D4

7.2.1 The opposition division decided that amended claim 1 of the third auxiliary request before it lacked novelty in light of D4 because the device disclosed in Figure 4B of D4 anticipated all the structural and functional features recited in the claim. In particular, the opposition division held that this specific device was suitable for arranging in a horizontal wellbore, as required by claim 1 (point 17 of reasons).

7.2.2 D4 discloses, in Figure 4B, a sealing ring 43 which is made of an elastic material in compression, and has been placed on the outside of a casing 42 prior to inserting it in the borehole 41 (page 18, line 30 to page 19, line 8). A cement sheath 431 is formed above and below the sealing ring 43 to confine the ring and maintain it under compression (page 18, lines 10 to 13). To obtain compression, the sealing material may include swellable material which is continuously fed to the ring down a line 421 at the back of the casing 42. The cement sheaths 431 form a cast material in the sense of claim 1. Based on the above interpretation of the feature "device", the sealing ring 43 can be seen as a device in the sense of claim 1. As shown in Figure 4B, the sealing ring 43 expands into a space which is not filled with cement, as required by claim 1. This space is defined by the cement sheaths above and below the ring. However, this drawing fails to show that cement is disposed radially between the ring 43 and the borehole and in contact with the ring.

7.2.3 The opposition division argued that casing 42 was cemented by using a conventional cementation technique, as mentioned on page 21, lines 1 and 2 of D4, that this technique involved pouring cement slurry down the annulus and that it was thus inevitable that cement was "disposed radially between and in contact with the borehole and the device" and that it "at least partly defined" a space not filled by cement.

7.2.4 The Board agrees with the appellant that these arguments are not persuasive:

7.2.5 Conventional cementing operations normally involve pumping cement slurry down the casing and then up the annulus, but not pumping cement down the annulus. This latter technique is known as "reverse-circulation cementing" and is normally used only for critical formations.

7.2.6 As submitted by the appellant, it cannot be derived from D4 that the casing 42 shown in Figure 4B is cemented by reverse-circulation cementing to form the cement sheaths 431. However, the Board is not convinced by the appellant's argument that the lower cement sheath 431 is formed by conventional cementing, while the upper cement sheath 431 is formed by reverse cementing, because D4 lacks any hint or incentive to use this latter technique and it is normally used only in certain exceptional circumstances. Rather, it is apparent that the casing 42 is cemented by the conventional cementing technique illustrated in Figures 6A and 6B of D4 and that, once the cement slurry has been placed in the annulus, the sealing ring 43 is expanded, via line 421, to displace the slurry and thus seal the annulus (page 21, lines 1 to 7). As explained by the appellant, it would not be practical to form the cement sheaths 431 by conventional cementing after expanding the sealing ring.

7.2.7 Notwithstanding the above, the Board is of the opinion that it can be derived from D4 that, due to changing conditions in the borehole or events such as completion operations, the sealing ring 43 may expand in an uncemented space of the cemented annulus, as required in claim 1.

7.2.8 Indeed, it is the general aim of D4 to provide systems and methods for maintaining zonal isolation in a wellbore, whereby a sealing element is kept under compression after completion of its placement (see e.g. claims 1 and 36), to accommodate any likely conformational, pressure or temperature changes of the surrounding wellbore portion by contracting or expanding in response to these changes (page 5, lines 13 to 16). It is expressly stated in D4 that, if a fluid pathway were to be created by cement fractures or micro-annuli formed at at the cement/casing interface and/or at the cement/formation interface, the sealing element would deform and block this pathway hence preventing any fluid migration along the wellbore (page 5, lines 16 to 21).

7.2.9 This general teaching of D4 must hold true for the preferred embodiment of the sealing element shown in Figure 4B. The Board thus considers that D4 discloses that, after casting, a cement fracture or micro-annulus may develop at the cement/formation interface with the inevitable consequence that the ring 43 will expand in this space unfilled with cement to re-seal the annulus.

7.2.10 Finally, since the sealing ring 43 is preferably made of water absorbent gels such as cross-linked polyacrylate or polyacrylamide, or organic swellable material such as high swell neoprene or nitrile, it is inherently capable of swelling on contact with a fluid present in this uncemented space, as required by claim 1.

7.2.11 Be that as it may, as explained above, claim 1 is not directed to a sealing device per se, bur rather to a well comprising a casing cemented in a borehole and a sealing device. The amendment according to the appellant's sole request results in that the claimed well comprises a cemented horizontal borehole. For this reason, the well with a vertical borehole as shown in Figure 4B of D4 cannot anticipate the claimed subject-matter.

7.2.12 In addition to this well with a vertical borehole, D4 discloses wells with horizontal boreholes, but they are in open-hole completion, wherein the production tubing is not cemented in place and zonal isolation is achieved by using packers (page 3, lines 13 to 17 and Figures 2A and 2B).

7.2.13 Notwithstanding the above, the Board shares the appellant's opinion that it cannot be derived from D4 that the sealing ring 43 can be adapted for use in the claimed manner. In fact, it is indispensable for the proper functioning of the sealing ring 43 that it is effectively confined between two cement sheaths 431, and it is unclear how such cement sheaths could be formed on either side of the ring 43 in a horizontal borehole.

7.3 Document D3 does not disclose a well with a vertical borehole. It discloses a drain pipe 11 which is cemented in a vertical borehole 12 and a deformable packer for sealing off the annulus between the drain pipe and the borehole, wherein the packer consists of a jacket 16 of a chemically expandable material which expands on contact with water and naturally occurring brines. D3 fails to disclose that the cast material is disposed radially between the device and the borehole, and that the device is in contact with the cast material.

7.4 Document D5 does not concern a well with a vertical borehole. It discloses, in Figures 4 and 5, a vertical borehole 16 and a casing 10 carrying a lower bracelet 12 including expandable material 24, e.g. sponge, rubber or bentonite, and an upper bracelet 12 including expandable material 24, preferably dry cement which - after dissolution of a bracelet coating - mixes with drilling fluid 26 to produce a cement slurry 28 in the annulus. The two bracelets are wrapped in a compressed state around the casing 10 before running it in the borehole 16. The lower bracelet 12 is allowed to expand against the borehole wall to support the cement slurry 28 (column 3, line 29 to column 4, line 8, in particular column 3, lines 55 to 62). As shown in Figure 5, the lower bracelet 12 expands into a space which is not filled with cement 28 and is partly defined by the cement placed above the bracelet. However, this space does not form a space in the sense of claim 1. In fact, no cement is disposed radially between the borehole and the lower bracelet 12 because it abuts the borehole wall about its entire circumference to prevent any cement slurry from flowing past.

7.5 Document D6 does not disclose a well with a vertical borehole. It discloses, in Figure 6, a vertical borehole 12 having a capped-off well casing 10 therein which is used to monitor and measure the level of ground water or a water table level 30 which changes from time to time. To seal the annulus 21 between the casing 10 and the borehole wall 23 and thus prevent water seepage from openings 16 in the strata above the water table level 30, annular sealing elements or disks 20 of liquid-swellable material are deposited to move down the borehole guided on the casing 10 to fill the annulus. The disks 20 are adapted to absorb water leaking into the borehole and then expand radially outwardly and inwardly to tightly clamp around the casing 10 and against the borehole wall 23 (column 8, lines 3 to 46). At ground level the upper end of the casing 10 is surrounded by a concrete cap 32, which can be seen as a cast material in the broad sense of claim 1. The uppermost disk 20 expands into a space which is not filled with concrete and is at least partly defined by the concrete. However, this space does not anticipate the space of claim 1. In fact, no concrete is disposed radially between the disk and the borehole, and no concrete is in contact with the disk.

8. Inventive step

8.1 The appellant shares the view of the opposition division that Figure 4B of D4 forms a realistic starting point for the assessment of the inventive step of the subject-matter of claim 1.

8.2 However, it is unrealistic to start from Figure 4B of D4 for a development towards the claimed invention. Indeed, contrary to the claimed well with a horizontal borehole, Figure 4B of D4 concerns a well with a vertical borehole. The skilled person could further develop that well but at the end of that development the well would still be a well with a vertical borehole. In general, although the skilled person is essentially free in choosing a (realistic) starting point for a development towards the claimed invention, that choice defines the framework for further development.

8.3 The Board is of the opinion that a promising and realistic starting point for the assessment of inventive step is a well with a horizontal borehole, a casing cemented therein and an uncemented space in the form of a fluid channel along a lower portion of the cemented annulus. Such a well is generally known in the art and described in the opening paragraphs of the patent, but not disclosed in the cited prior art documents. In particular, the horizontal boreholes disclosed in D4 and D12 are in open-hole completion.

8.4 The subject-matter of claim 1 differs from this generally known prior art essentially in that it comprises a device which has expanded into the space for sealing the annulus, the device comprising an annular sleeve of expandable material which has been disposed on the casing and arranged in the annulus before cementing to eventually expand into the space not filled with cement, and has swelled on contact with a fluid present in the space, or by diffusion of this fluid into the sleeve.

8.5 The problem objectively solved by these distinguishing features can be seen as how to prevent or reduce uncontrollable fluid transport in the cemented annulus (see page 2 of the application).

8.6 The Board is not persuaded that in light of the cited prior art documents the skilled person, in the expectation of solving this problem, could and indeed would dispose a sleeve of expandable material on the casing to properly position the sleeve before cementing, i.e. before the uncemented space is formed, so as to arrive at the claimed invention. As explained above there is a large degree of chance that determines whether or not such a space not filled with cement will be formed in practice.

8.7 In conclusion, with regard to the prior art cited by the opponent, the Board is of the opinion that the subject-matter of claim 1 involves an inventive step in the sense of Article 56 EPC 1973.

8.8 The above reasoning applies mutatis mutandis to the subject-matter of method claim 3.

9. The description has been brought into conformity with the amended claims.

10. The Board comes to the conclusion that the patent documents according to the (sole) request meet the requirements of the EPC.