BP will keep the cap closed for at least 24 more hours on its ruptured oil well in the Gulf of Mexico, Coast Guard Adm. Thad Allen said in a news conference Monday afternoon. The cap has been closed since Thursday, keeping new oil from flowing into the Gulf — for now. But scientists and engineers have been keeping a close watch on the well during that time, constantly monitoring pressure levels inside the well and data from the seafloor to make sure that the well is staying intact.
On Monday, Allen said that small amounts of oil and gas are leaking from the cap and that scientists have discovered oil seeping from the ground about two miles away from the well, but said “there’s no indication at this time that this indicates a […] problem in the well bore.”
The announcement follows a weekend of back-and-forth between BP and federal authorities. On Sunday night, Allen sent a letter to BP Managing Director Bob Dudley instructing the company to improve its monitoring of the well and its surroundings. It noted “anomalies” found near the wellhead and an oil seep nearby. Allen wrote:
“As a continued condition of the test, you are required to provide as a top priority access and coordination for the monitoring systems, which include seismic and sonar surface ships and subsea ROV and acoustic systems. When seeps are detected, you are directed to marshal resources, quickly investigate, and report findings to the government in no more than four hours.”
On Monday, Allen said that the government was satisfied with the answers it had received from BP and that the well could remain closed for at least 24 more hours.
He said that the government does not believe that oil and gas seeping up from the seafloor about 2 miles from the wellhead is associated with Macondo well. It could be a naturally occurring seep, many of which dot the Gulf.
“If it’s just a natural seep it’s probably not a problem,” University of Houston petroleum geology professor Don Van Nieuwenhuise told The Rundown.
Scientists and engineers are keeping watch over an array of data while the well remains closed. The worry is that keeping the oil bottled in at the top of the well could cause it to leak out elsewhere through cracks in the well bore, or new fissures in the reservoir. So they’re monitoring the pressure in the well to make sure that it doesn’t drop too low — which would indicate the oil escaping elsewhere.
From the beginning, authorities said that if the pressure hit 7,500 psi it would indicate that the well was intact. If it went below 6,000 psi, it would indicate that cracks or other damage to the well was allowing oil to escape. So far, the pressure has remained in the indeterminate range between those two numbers. On Monday afternoon it was 6,811 psi, and gradually rising a pound or so every hour, Allen said.
The fact that it’s increasing slightly over time — rather than decreasing — is a good sign that there’s not a leak, says David Rensink, incoming president of the American Association of Petroleum Engineers.
But scientists are concerned that the original pressure when the cap was first placed on was lower than the expected 7,500 or so. They had calculated that expected pressure based on what they knew the pressure in the reservoir to be before the blowout, explains Greg McCormack, head of the Petroleum Extension Service at the University of Texas. The lower-than-expected pressure reading could be because of a leak, but it could also be that months of oil flowing into the ocean had depleted the reservoir enough to lower the starting pressure.
Scientists and engineers are also monitoring the area around the well with remote-operated vehicles, both visually and with seismic tests. Those tests work by sending sound energy down through the rocks. The presence of oil or gas affects the way that the energy travels through the rocks and bounces back, so engineers can tell if oil and gas are present.
Allen said Monday that such monitoring had identified some “anomalies” between 80 and a couple of hundred meters from the well head — but that none so far were considered consequential.
Still, Allen said that it was not yet clear whether the well cap would be able to remain on until the relief wells are finished, or whether BP will need to eventually open the cap and go back to a system of capturing and processing the oil on surface ships.
“We are going on a day-to-day basis,” he said. “So I’m not prepared to say the well is shut in until relief well is done. There are too many uncertainties.”