Blowout Suspected in Deepwater Horizon Oil Rig Explosion

Little more than a week after the Deepwater Horizon oil rig explosion that likely killed 11 men and caused a massive oil spill, it is still not known what caused the disaster. Speculation is that the explosion was the result of a blowout. Such an event occurs when a combination of well control systems – primarily drilling mud hydrostatics and blow-out preventers (BOPs) – fail.

According to The Christian Science Monitor, the Deepwater Horizon rig is one of the most advanced engineering feats in the world. It has drilled deeper than any other waterborne platform. It’s giant, flexible “drill bit” can probe oil deposits up to 32,000 feet deep.

In deep water drilling operations like Deepwater Horizon, most of the well control system is installed at the sea floor. As such, all equipment must be installed remotely using electro-hydraulic controls and Remote Operating Vehicles (ROV) with video cameras. Earlier in the disaster, BP was using ROV in an attempt to reach and close the BOP valves at Deepwater Horizon. That fact has led to speculation that the well control systems on Deepwater Horizon failed for some reason.

Oil and gas located at the depth where Deepwater Horizon was drilling at the time of the explosion can be as hot as 450 degrees and at pressures 2,000 times atmospheric. The fire that occurred after the explosion was fueled by oil and gas. This is evidence that there was some abnormal pressure buildup in the well, the Monitor said.

According to a BusinessWeek report, in an operation like the one involving Deepwater Horizon, drilling mud is used to lubricate drill bits as they make their way through rock. This mud is constantly circulated through the wellbore, pumped up to the surface where rock “cuttings” are removed, then injected back down.

Importantly, this mud also acts as a kind of plug in the hole, preventing any oil and gas from blasting up out of it. For whatever reason, it appears that in the case of Deepwater Horizon, the drilling mud could no longer control pressure in the well, allowing fluid to flow into the wellbore and up the annulus and/or inside the drill pipe – an event called a kick.

If the mud is unable to contain the flow of oil, crews must close the BOP valves. If the BOP valves fail, a kick can quickly escalate into a blowout when the formation fluids reach the surface. The gas and other hydrocarbons escaping from the well would have ignited, leading to the devastating explosion and fire on Deepwater Horizon.