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Recent blowout one of only 18 in state Alaska Oil and Gas Conservation Commission says uncontrolled flows of gas, oil rare in Alaska — 10 on slope, eight in Cook Inlet Kristen Nelson Petroleum News
After Aurora Gas had a blowout while drilling its Moquawkie No. 4 gas well in late September, Petroleum News checked with the Alaska Oil and Gas Conservation Commission to find out how common blowouts are in Alaska.
Turns out, not common at all, AOGCC commissioners said in a November interview, particularly in recent years with modern drilling technology and drilling experience in Alaska’s major oil and gas basins.
The blowout Aurora had, in which they hit an unexpected shallow gas pocket while drilling, forcing drilling mud back up and out of the drilling hole, was controlled in less than 24 hours. The commission said both the unexpected shallow gas pocket and the quick control are typical of the blowouts that have occurred in Alaska.
Defining blowouts as events that occur when a well is being drilled or completed and while there is a rig on the well, the commission identified 10 blowouts on the North Slope — the most recent of which occurred in 1994 — and eight in the Cook Inlet basin, the most recent this year, but the last prior to that in 1987.
These are known blowouts over the period of modern drilling in Alaska, beginning in 1949 on the North Slope and in 1962 in the Cook Inlet basin.
The commission is investigating the Aurora blowout and had no comment on that event, other to confirm that the rig encountered unexpected shallow gas and that a diverter was in place.
“That would be the secondary protection, if the well did blow out and before you set surface pipe, surface casing, you have a diverter,” said Dan Seamount, the commission’s chair and the geologist on the three-member panel.
The Department of Environmental Conservation, Division of Spill Prevention and Response, described what happened at the Aurora Moquawkie No. 4 development gas well on the west side of Cook Inlet, west of Tyonek in an incident report: “An unexpected shallow gas pocket was encountered during the drilling of a gas well, which forced the drilling mud to back up and flow out of the drilling hole. The mud was diverted through a diverter line which directed the fluids to the edge of the pad to prevent damage to the drilling rig.”
Aurora well controlled quickly Scott Pfoff, president of Aurora Gas, told Petroleum News in an e-mail that the Moquawkie No. 4, which blew out Sept. 28, was under control by Sept. 29. “In fact, the well was killed and back to ‘normal operations’ within 24 hours of going on diverter,” he said. Killing the well refers to stopping the flow to surface.
Aurora considers what happened to have been a “diverter incident,” he said, since “everything worked as it was supposed to (and we had all the required equipment on the well) — the gas was diverted away from the rig, there was no fire, etc.” Pfoff said in early October that since getting the well back to normal operations Aurora had run and cemented surface casing and was ready to resume drilling.
DEC said some 11,000 gallons of drilling mud were displaced, some 2,500 gallons of which were contained in the well cellar and around the drilling rig. Those fluids were recovered using the “super sucker,” the agency said, adding that mud was being collected at the end of the diverter line and would be re-injected. In a final report, on Oct. 15, DEC reported that mixtures of heavier drilling mud were injected into the well to maintain pressure and stop the flow of gas, which was accomplished the evening of Sept. 29. A silt fence was placed between the drilling mud and the nearby creek to prevent any drilling mud reaching the creek. “All visible mud from this area has been collected using a super sucker,” DEC said, with some 8,800 gallons of mud and water collected from off the pad.
DEC said there was no indication of impact to the nearby creek and no observed impacts to wildlife.
Commission organizing data Seamount said the commission is organizing the information it has on blowouts and he invited knowledgeable people with experience of blowouts in the state to contact him with additional information. (See sidebar for list of blowouts.) He said the information would probably be summarized on a spreadsheet which would include data such as the well name, dates — how long the blowout lasted, the fluid involved and the reason for the blowout.
The earliest known blowouts in the state occurred in the 1940s and 1950s, when the U.S. Navy was drilling in what was then Naval Petroleum Reserve No. 4, now the National Petroleum Reserve-Alaska, on the west side of the North Slope. Seamount said those early blowouts “were mainly due to poor drilling practices which are not used today.”
“We wouldn’t let them drill the way they drilled back in the ‘40s and the ‘50s especially ... the U.S. Navy — they would drill without surface casing or without intermediate casing ... and that caused a number of blowouts,” he said.
The blowouts in the petroleum reserve, Simpson Core Test Nos. 16 (1949) and 26 (1950), for example, occurred with no casing or conductor pipe set in the wells.
Technology and experience Commissioner Cathy Foerster, the petroleum engineer on the commission, said the three things that make the biggest difference in the reduced number of blowouts are, “in order: technology, experience and regulation. ... We wouldn’t let them drill the way that they’d do it back then; but they wouldn’t want to, either, because of technology and experience.”
She said regulation is the third factor, behind improved technology and experience.
New technology prevents most of the conditions that resulted in past blowouts, Seamount said: seismic is better at identifying shallow gas; there is drilling experience in most areas; pressure is now measured while drilling; there is early kick detection — detection of gas coming back with the mud — in the mud pit; and there is more accurate wellbore collision avoidance, less likelihood of running into an existing wellbore while drilling.
While there have been no blowouts at Point Thomson on the eastern side of the North Slope, Foerster said early well control incidents — where the operator succeeded in keeping wells under control so no blowout occurred — illustrate the experience factor. Alaska State A-1, drilled by Exxon on Flaxman Island in 1975, hit abnormal pressures below 12,000 feet. Foerster said she didn’t think they expected what they got, because they had set casing at 3,370 feet — “and they were drilling ahead with open hole when they encountered an abnormal pressure zone at 12,463 feet.”
It was in 1975, she said, “but they’re drilling with thousands and thousands of feet of open hole in this area where they don’t know anything and they have a problem.”
The next well control situation in the Point Thomson area occurred six years later at Challenge Island No. 1, with a different operator — Sohio Alaska Petroleum (now BP) — but knowing what Exxon encountered, they had pipe set to 10,390 feet, so with the earlier experience, Foerster said, they’d modified the plan. They still had well-control issues, but they’d learned from the earlier well and added an extra string of pipe: “As you get your experience, you put your coping mechanisms in place,” she said.
A beacon and a lawsuit Two of the blowouts in Cook Inlet, both in 1962 at Pan American-operated wells, were notable, one visually, the other legally.
Cook Inlet State No. 1 was the state’s most visible blowout: the gas was flared and since it took more than a year to bring the well under control, the burning gas became a beacon for pilots in Cook Inlet. It produced a flame visible in Anchorage, said Commissioner John Norman, an attorney who is the public member of the commission and a former chair.
“That one was of interest because much of the greater part of the population of Anchorage could look out and see it,” he said.
Drilling was started on a relief well within a week of the blowout, but the well burned through the winter of 1962-63 because winter ice in the inlet prevented completion of the relief well until spring, with drilling suspended at the relief well in November when ice pushed the drilling barge off location.
Drilling on the relief well resumed in April but the original well wasn’t killed until Oct. 23, 1963, more than a year after the blowout began Aug. 22, 1962.
The blowout with the legal history was Middle Ground Shoal State No. 1, Norman said, which blew out June 10, 1962, and was killed July 24. Pan American plugged the well, but later filed with the state for a discovery royalty certification — providing a reduction in royalty to 5 percent for production for the first 10 years for the discovery well on a structure, in this case Middle Ground Shoal.
Shell Oil drilled on land immediately adjacent to Pan American’s lease, completed a well and subsequently filed for — and was denied — a discovery royalty certification. Shell argued that since the Pan American well was plugged, while its own well was completed, that it should receive the royalty reduction.
Shell appealed; the Superior Court found in its favor and the case was appealed by Pan American and the State of Alaska to the Alaska Supreme Court, which found in Pan American’s favor, confirming the state’s original decision.
5,570 North Slope wells completed There are no guarantees there won’t be a blowout, Seamount said, but 5,570 wells have been drilled on the North Slope in modern times, and “it’s been over 10 years since the last blowout” on the slope, which was at Endicott in 1994.
“My impression is that an awful lot goes right in a lot of the work of the agency and the industry,” Norman said. As technology has become increasingly sophisticated it has averted incidents like blowouts, he said.
“A great deal has and is being done right all across Alaska, day after day: Valves are working as they should; (there is) redundancy, blowout prevention,” Norman said.
Foerster said Aurora’s recent blowout at Moquawkie “is unusual.” The commission is investigating, she said, “and if we find that good oilfield practices weren’t employed or any of our regulations or stipulations weren’t followed then we’ll take appropriate action.”
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