AOGCC proposes new regulations on blowout control plans
A blowout preventer, or BOP, is the mechanical device intended to control and close off a well if there is an uncontrolled flow of oil and gas. The BOP is positioned at the top of a well and just under the drilling floor of the rig while the well is being drilled. It contains mechanical “rams,” which are to be closed if there is an uncontrolled flow of fluids up the well. The rams seal off the well, preventing the oil and gas from reaching the rig floor where a fire or explosion might occur or from where oil might spill off the rig into the environment.
The drilling fluid, or the “mud” is the first line of defense against a blowout. As the well is drilled, mud is pumped down the drill string to the drill bit at the bottom and returns up the well-bore in the space, or annulus, between the outside of the drill pipe and the casing, or the larger-diameter pipes, that line and protect the well.
The column of drilling fluid being pumped down, which would be a mile or more long when a well extends to 5,000 to 10,000 feet or more, has considerable weight and exerts a tremendous downward hydrostatic pressure in the well.
At the bottom, where there is an “open hole” with no casing, the circular tubing through which the well drilled, the hydrostatic pressure provides an “overbalance” of pressure that exceeds the natural pressure of the reservoir into which the well is drilled. The overbalance of pressure prevents oil and gas fluids from entering and coming up the well bore.
Sometimes the drillers encounter a gas “kick” or a surge of unexpected high pressure if they encounter a pocket of high-pressure gas. Shallow gas pockets are the cause of all of Alaska’s blowouts, except one.
Instruments in the well typically detect a rapid gas and pressure buildup and the drillers can counter this by closing the BOP and pumping heavier fluids under higher pressure through a choke, or restricted pipe, in the BOP. This is to overcome the pressure of the petroleum fluids and pushes them back down the well, bringing it under control.
Surveys of drilling locations are required to detect shallow gas hazards but sometimes drillers can be unpleasantly surprised. However, improvements in seismic technology, which can detect shallow gas hazards, and the increased regulatory scrutiny has greatly reduced the chances of a blowout in recent years.
If the unexpected upward flow of fluids is not brought under control, a blowout can result, potentially pushing the steel tubing, or pipe, back up out of the well, damaging the well, the rig and potentially causing loss of life or injuries to the drill crew.
The primary danger is the oil and gas itself, which are flammable and explosive. The mud system and the pressure it exerts is the primary method for controlling the well. The blowout preventer is a final defense, and a vital one.
Blowout preventers are used on both land and offshore rigs. In both cases the BOP is secured to the top of the wellbore. With a deep offshore well this would be at the sea bottom, with a “riser” or flexible pipe extending up to the drill rig on the surface. The riser provides a secure and enclosed path for the drill string, which rotates to drill the well, and drill fluids, or muds, that are pumped down the well to control pressure and then recirculated back to the rig at the surface.
The state of Alaska is considering strengthened regulatory controls on offshore drilling with a new requirement for operators to have a blowout control plan.
A recommendation to change the state’s drilling rules comes at the end of a lengthy review of the state’s drilling safety rules by the Alaska’s Oil and Gas Conservation Commission, said Cathy Foerster, one of the three AOGCC commissioners.
AOGCC is a quasi-judiciary independent state regulatory agency that oversees drilling and other oilfield safety and production practices in Alaska, including state-owned submerged lands to the three-mile territorial limit.
The Alaska Department of Environmental Conservation now requires drillers to have approved contingency plans in place to control oil spills, including large spills from a blowout. The proposed AOGCC rule would be specific to blowout control, however, and would be reviewed by the commission’s staff, where there is expertise on drilling.
The proposal came about because of concerns on the Macondo well, where a blowout preventer on the Deepwater Horizon rig failed to function. The resulting explosion and fire killed several people, destroyed the rig, and caused one of the worst oil peacetime spills in the history of the industry.
“The state of Alaska’s drilling rules, implemented through the AOGCC, were very strong even before Macondo – stronger that the federal government’s, in fact – and a detailed post-Macondo review of regulations by the AOGCC and outside experts revealed no major flaws except in one area, a specific requirement for a plan to control a blowout,” Foerster said.
Foerster said she believes Alaska is the only U.S. state to conduct a detailed review of drilling regulations following the Gulf of Mexico disaster.
The commission also is adding to its staff of inspectors and drilling engineers because of the greater scrutiny that the state is now giving drilling operations, she said.
The state commission decided to do its review because some of the problems in well safety that were identified in deep ocean wells like Macondo could also occur in ultra extended-reach wells drilled in Alaska, such as at BP’s planned Liberty project, where wells would be drilled out as much as eight miles laterally from the surface location of the drill rig.
Extended-reach wells are routinely drilled in Alaska, although not to the distances planned at Liberty. Extended-reach wells were drilled by ExxonMobil at Point Thomson and by BP and at the Milne Point and Niakuk fields near Prudhoe Bay.
Well blowouts have happened in Alaska, although they are rare. So far the blowouts in the state have been on gas rigs, not oil, and there has never been a case of oil released in an Alaska blowout reaching the land surface or open water, Foerster said.
Since 1962 there have been four offshore blowouts in Cook Inlet, all involving releases of gas, the last in 1987. On the North Slope, there have been seven blowouts that have occurred in approximately 5,000 wells drilled since the Prudhoe Bay oil field was discovered in 1967. None of them involved a release of crude oil, and none caused injuries, Foerster said.
State rules require the testing of blowout preventers every seven days on exploration wells being drilled and “workover,” or maintenance well, and every 14 days on new production wells being drilled. Test results must be filed with the commission.
AOGCC inspectors are also on-scene to witness many tests. The commission’s records indicate that state inspectors attend tests of well control systems on every active drill rig in the state once every two months. The AOGCC’s data shows a “pass rate” of 98 percent for blowout control equipment.