Former ICTY prosecutor finds no evidence of criminal conduct in Chiren drilling dispute, as EPPO investigation continues.

An independent review by Steven Kay KC, one of Britain’s most experienced criminal barristers and a former senior prosecutor at the International Criminal Tribunal for the former Yugoslavia, has found no evidence of criminal fraud in connection with the design changes at the centre of a long-running controversy over the expansion of Bulgaria’s Chiren underground gas storage facility, one of the European Union’s most strategically significant energy security projects.

The review, commissioned by project contractor GBS, concludes that the disputed changes to the drilling programme were permitted under the terms of the procurement framework, and calls into question whether the allegations that have shaped both public reporting and a subsequent investigation by the European Public Prosecutor’s Office (EPPO) were based on a complete reading of the contractual and technical record.

A cornerstone of Europe’s post-invasion energy strategy

Chiren sits at the centre of Bulgaria’s energy infrastructure strategy and forms part of the EU’s broader push to shore up regional energy resilience since Russia’s invasion of Ukraine. Financed with EU and US support, the expansion is designed to lift Bulgaria’s gas storage capacity, strengthen supply security across south-eastern Europe, and cut reliance on Russian gas.

From subcontractor complaint to EPPO investigation

The project became mired in controversy after claims emerged that GBS had altered the technical design of the drilling programme after the contract was awarded, in breach, critics said, of Bulgaria’s public procurement rules and with implications for safety. The allegations were originally made by the Mining and Energy Forum and the Anti-Corruption Fund, before being taken up by investigative journalists, and ultimately became the subject of an ongoing EPPO probe. No charges have been brought. The original drilling contract between Bulgartransgaz (BTG) and GBS’s project subsidiary, UGS, was suspended during the investigation and later terminated by mutual agreement.

At issue is whether GBS’s shift from directional to vertical drilling made after contract award, and one that generated significant cost savings without any change to the contract price, amounted to an unlawful post-award alteration of the procurement, or a legitimate exercise of a process the contract itself anticipated. GBS has consistently maintained that the change followed updated geological modelling required under the procurement documents, was technically justified, and was approved by BTG throughout.

What the review found

Rather than simply weighing the parties’ competing accounts, Kay’s review examined the underlying procurement documentation, contractual framework, technical specifications and geological modelling directly. Its central finding is that the contract did not, in fact, mandate directional wells. While one part of the technical specification referred to directional drilling, other provisions required the contractor to complete updated geological modelling before the final well design, directional or vertical, was determined, subject to BTG’s sign-off. On that reading, the switch to vertical wells was not a departure from the contract but a step the procurement documents themselves contemplated. The review further finds that the geological modelling carried out during the project supported the move to vertical wells on technical grounds, and that the resulting design decisions were consistent with both the procurement framework and the underlying contractual arrangements.

Kay’s conclusion is unambiguous: he found “no evidence of dishonesty and any other form of criminal conduct,” characterising the dispute as a commercial disagreement over contractual rights and technical specifications rather than a matter for criminal law.

A narrative built on selective reading, review finds

The review is also critical of how the underlying allegations have been reported and campaigned on, concluding that claims advanced by campaign groups and repeated in media coverage drew on selective readings of the procurement documentation that did not account for the contractual framework as a whole, or for the technical analysis behind the revised well design. In particular, it finds that insufficient weight was given to the provisions expressly contemplating that the final drilling methodology would only be fixed once updated geological modelling was complete.

None of this brings the EPPO investigation to a close, and the review does not address separate allegations of political interference that have also surrounded the Chiren project. Its significance lies instead in testing and challenging the legal and technical assumptions that have underpinned the public narrative around one of the EU’s most strategically important energy infrastructure schemes.

Implications for investor confidence in EU energy infrastructure

The findings arrive at a moment when Europe’s energy security agenda depends heavily on investor confidence in exactly this kind of large-scale infrastructure delivery. With the original Chiren contract suspended for the duration of the EPPO investigation before being terminated by mutual consent, the review raises a wider question that will resonate well beyond Bulgaria: what happens to strategically critical projects, and to the investors and contractors who deliver them, when procurement disputes escalate into criminal investigations before the underlying contractual and technical evidence has been independently tested. As the EU’s accession and energy-security ambitions in south-eastern Europe continue to depend on the credibility of exactly this kind of infrastructure delivery, the Chiren case is likely to prompt renewed scrutiny of how such allegations are assessed, investigated and reported, and of the consequences for project delivery and investor confidence when they are not.

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