Offshore oil spill prevention and response

[1][2][3] Important aspects of prevention include technological assessment of equipment and procedures, and protocols for training, inspection, and contingency plans for the avoidance, control, and shutdown of offshore operations.

[5] Currently administered by the Minerals Management Service (MMS), these regulatory functions were ordered on May 19, 2010 to be transferred to the United States Department of the Interior's newly created Bureau of Safety and Environmental Enforcement.

As William Cook, former chief of the Performance and Safety Branch of Offshore Minerals Management for the MMS, expressed it: "Technology is not enough.

Technology—in particular—new, innovative, cutting edge technology must be integrated with human and organizational factors (HOF) into a system safety management approach.

Today, there are several regulations, such as the clean water act, and International Convention on Civil Liability for Oil Pollution Damage (CLC) that provide a framework for how to deal with the issue of compensation.

During the different phases of drilling, production, workover and abandonments, many different pieces of equipment will be used to maintain control of the well fluids and pressures.

[14] Blowout Preventers often contain a stack of independently-operated cutoff mechanisms, so there is redundancy in case of failure, and the ability to work in all normal circumstances with the drill pipe in or out of the well bore.

This study was designed to answer the question "Can a given rig's BOP equipment shear the pipe to be used in a given drilling program at the most demanding condition to be expected?

"[18] Seven of the fourteen cases in this study opted not to test, another had insufficient data to draw a definitive conclusion, and three failed to shear the pipe under realistic conditions of expected well bore and seawater pressure.

[18] A follow-up study in 2004 confirmed these results with a much larger sample of drill pipes and typical blowout preventers from three different manufacturers.

[19] Casing of offshore oil wells is done with a set of nested steel pipes, cemented to the rock walls of the borehole as in Figure 4.

[20] Failure of either the casings or the cement can lead to injection of oil into groundwater layers, flow to the surface far from the well, or a blowout at the wellhead.

[20] Without centralizers, there is a high risk that a channel of drilling mud or contaminated cement will be left where the casing contacts the borehole.

This can be the result of a rushed drilling schedule, or it could happen if there is a leak causing the cement to creep during the time it is supposed to be setting.

While there is no requirement for such barriers, adding them can minimize the risk of a blowout through a direct wide-open channel from the reservoir to the surface.

Inspector on offshore oil drilling rig
Figure 1. Of the shear rams tested, 50% failed under pressures expected in deep sea drilling.
Figure 2. In a shear ram, the two blades are driven hydraulically to cut the thick steel drill pipe.
Figure 3. Sheared end of a drill pipe.
Figure 4. Typical well casings during the final tests before shut in.