Cement contractor Halliburton recently filed a lawsuit against BP asserting that Skripnikova’s statements prove the oil giant knew about the shallower gas before the explosion and should have sought a new cement and well design. BP has denied the allegations.

Skripnikova’s job involved analyzing data from BP’s Macondo well to determine the depth and characteristics of oil and gas deposits, which in turn is used in a process called temporary abandonment, when wells are sealed so they can be used for production later.

Based on the initial information, regulators approved BP’s well sealing plan, which called for placing the top of the cement at roughly 17,300 feet below the surface of the water. The cement was pumped April 19, the day before the explosion. But Skripnikova said that after she flew back from the rig she and others re-examined the analysis, and on the day of the explosion she identified the shallower gas zone. That would have meant the cement should have been placed at just under 17,000 feet below the surface of the water.

She said she did not relay that information to drilling engineers on the Deepwater Horizon and warn them to hold off proceeding with the abandonment. She suggested in her deposition that she thought the information would be passed up the chain. BP was already $60 million over budget and stopping operations at that point and coming up with a new cement design would have meant millions of extra dollars in costs.

Later in the deposition, Skripnikova backtracked and said the new analysis was not discussed among her team until the day after the explosion.