They quickly learned otherwise.

BP allowed Mr. Silverman to conduct a confidential deposition about the well with a BP executive, David Jenkins. Reached by The Times, Mr. Jenkins said his memories were vague, but he recalled the deposition — which was sealed by the court — and telling Mr. Silverman that “there was never any evidence at all, at that stage, that there was anything material within the refuge.”

Mr. Silverman, similarly, remembered being convinced that “either there was no oil and gas there, or the oil couldn’t be produced at an economic value.”

Some of the documents in the case are missing from the court file, perhaps lost over the decades. But in more than 1,000 pages of legal and regulatory filings, The Times discovered other hints that the findings were disappointing. Under oath, a Goldman Sachs banker who worked on the merger testified that BP had led him to believe that the test well results were “not particularly encouraging.”

John Warden, a lawyer who represented BP, said that he had only dim memories of the case but that the well results “became a nonissue.” Told of The Times’s reporting, he added, “It looks to me like you have gotten it right.”

Mr. Silverman hinted at the findings in a memoir he self-published 10 years ago, but has never before spoken out directly about what was said in the deposition. He said he was breaking his silence because of the Trump administration’s decision to open the refuge — protected by Congress for decades — for oil development.

“This is important for the whole country,” he said.

One dry hole does not necessarily mean there is no oil to be found, especially since some decades-old seismic tests indicate that the area may hold as much as 12 billion barrels’ worth. And knowledge of the area’s subsurface geology is valuable. But confirmation that the results of the only test well were discouraging could embolden opponents of drilling and prompt second thoughts among potential lease bidders.