IHS Global Insight Perspective | |
Significance | The "top kill" process, which involved pumping around 30,000 barrels of mud down the well at rates of 80 barrels per minute, was abandoned as the mud could not push the oil back down the well long enough for cement to be pumped into the shaft to seal it. |
Implications | The failure of top kill will heighten domestic outrage against BP. The company now hopes its capping solution will contain oil flows and prevent gas hydrate formation, which was a key reason for the failure of previous attempts to lower a containment box into the area. |
Outlook | The strategy is risky, particularly if cutting the kinked riser increases flow rates and if the lower marine rising package cannot be lowered onto the blowout preventer (BOP) stack; an immediate end to the spill is impossible given that cutting the riser will take between four and seven days and the company is also considering lowering another BOP onto the area or continuing relief well drilling to try to kill or contain the well. |
"Top Kill" Abandoned
BP has abandoned the "top kill" process aimed at plugging the Macondo well in the Gulf of Mexico. Top kill involves injecting huge quantities of mud to push the oil and gas back down the well with a view to halting the flow long enough to pump cement into the shaft to seal it. The operation commenced on the night of 26 May, but despite pumping more than 30,000 barrels of mud down the well at rates as high as 80 barrels per minute, and using materials such as chunks of rubber and fibrous pieces of rope to block flows, the pressure from the reservoir ultimately proved too strong. The mud was continuously dislodged by the flowing oil and at around 3.30 pm on 29 May, BP and government officials called a halt to the operation. The failure of top kill has heightened domestic outrage against BP and from the United States president Barack Obama, who stated that the disaster was as enraging as it was heartbreaking.
BP has now announced a new strategy involving sawing off part of the pipe, or riser, that extends from the drilling platform down to the sea floor. After cutting the riser, the device will be coupled to a flex joint above a container known as the lower marine riser package (LMRP), which will be lowered onto the blowout preventer (BOP) stack. The device would collect leaking oil from the top of the BOP, which could then be directed to a tanker floating on the sea. According to Upstream Online, the device will have a sealing grommet to keep water out of the flow and control gas hydrate formation. BP may hope that control of gas hydrate formation will help prevent clogging and ice build-up, as encountered when BP previously tried to lower a containment box onto the well (see United States: 28 April 2010: Investigation Launched Into GOM Oil Spill as Efforts to Stop Leak Continue). However, it is only expected to capture some of the escaping oil, as the seal between the LMRP and the BOP will not be tight. It is expected to take between four and seven days to cut through the pipe, a process that will be carried out by remote-controlled vessels using a diamond-toothed band saw, so an immediate halt to the flow is not possible.
Furthermore, there are risks associated with the capping plan. Reports suggest that a kink in the pipe is restricting the flow of oil, thus sawing the pipe may temporarily increase oil flows by as much as 20%, heightening environmental devastation, particularly if the LMRP cap cannot then be fitted onto the well due to increased flows or other technical issues. BP has deflected criticism of the plan, stating that its pressure data readings suggest there will not be a significant impact on flow rates from removing the kink. However, everyone is in unchartered territory with the Macondo well and the success of the LMRP remains uncertain.
Outlook and Implications
Looking ahead, the LMRP is more of a damage limitation exercise than a solution as, even if the attempt is successful, it will not plug the well but instead help to capture more oil and reduce environmental devastation. However, putting the cap in place might allow BP time to get on with other attempts to kill the well. Another option BP is looking at is lowering another BOP—or massive stack of shutoff valves—on top of the existing one. The existing BOP is reportedly still partially functioning and helping to restrict flows and a second properly BOP stack could conceivably provide further support.
BP also previously started drilling two relief wells at the site, which are high-cost, but as past experience appears to show are the most effective way to kill wells. A similar leaking subsea well in the Timor Sea was eventually killed through the drilling of a relief well, although the option is time consuming and could take multiple attempts to succeed. Intersecting the leaking well at such depths below the seabed is a hit-and-miss exercise and, in the case of the Timor Sea, took multiple attempts. At Macondo the drilling depths are far greater and the drilling target even smaller while the pace of environmental devastation is far more rapid. The two initial relief wells are only due to be completed in August and may not successfully intercept, thus there is a lot of pressure on BP to pursue a more immediate solution. Even if they do intercept, the failure of the top kill process raises questions about how successful attempts would be to pump concrete down the relief wells to halt the flow.
These are dark days for BP, the United States government and all those who are starting to suffer from the country's largest environmental catastrophe. At present future prospects for an early end to the disaster do not appear very favourable.