BP vice president Kent Wells said on a conference call that there was no evidence of a leak in the pipe under the sea floor, one of the main concerns. Wells spoke 17 hours after valves were shut to trap oil inside the cap, a test that could last up to 48 hours.
He said pressure continued to rise inside the tight-fighting cap, a sign that oil was gushing into it, instead of out through any undiscovered cracks, and staying there.
As of Friday, the pressure was more than 6,700 pounds per square inch, above the minimum they were hoping to see, but not yet in the high range of 8,000 to 9,000 psi they were hoping for.
"The pressures we've seen so far are consistent with the engineering analysis work that BP has done," Wells said. "It's been a very steady build."
Wells also said work would resume on two relief wells, the oil giant's more permanent solution meant to plug the well for good underground to end one of the nation's worst environmental catastrophes.
That's also a good sign that things were going well. Engineers had stopped drilling one of the wells Thursday in case that bore hole deep underground could be affected by the oil cap effort.
Engineers and scientists continue to monitor the cap's pressure. Wells said two undersea robots were combing the sea bed, looking for any trace of oil or problems on the floor.
It's still unclear whether the well cap will need to be reopened to allow oil to leak back after the test.
BP finally stopped oil from spewing into the sea Thursday, for the first time since an April 20 explosion on the BP-leased Deepwater Horizon oil rig killed 11 workers and unleashed the spill 5,000 feet beneath the water's surface.
But the cap is a temporary measure. Even if it holds, BP needs to plug the gusher with cement and mud deep underground, where the seal will hold more permanently than any cap from above could.