Drilling regulator: Well blowouts rare in Colorado, effects are mostly minimal
A Colorado oil and gas regulator says well blowouts are a rarity in Colorado, and any impacts generally are limited to the drilling site.
Stuart Ellsworth, acting engineering manager for the Colorado Oil and Gas Conservation Commission, reviewed the recent history of well-control problems for the commission last week, prompted by the ongoing BP oil spill in the Gulf of Mexico.
Ellsworth said wells drilled in Colorado generally tap lower-pressure formations than in the Gulf. However, there are some high-pressure areas, including the Rulison and Mamm Creek fields in Garfield County and a field in the Greeley area, he said.
Since 2004, at least three blowouts have occurred in the state. Those three all were in Garfield County, with two involving fires. However, Ellsworth’s review found that well-control incidents have caused only minor injuries, if any, and resulted in no spills. Any fire damage was limited to the rigs and well sites.
Ellsworth said state regulators are reviewing well-design-review procedures and inspection protocols.
Scrutiny of the Gulf spill has focused partly on the failure of a blowout preventer to stop it. Such devices commonly are used on Colorado wells, but they aren’t foolproof, and Ellsworth said they are just one element of well control.
The devices can close off the space surrounding a well pipe and bore, or the whole well. They are hydraulically operated by pumps and have backup pumps and a gas-pressurized system as a secondary backup, as well as a valve that can be manually operated.
Still, Ellsworth found a 2008 Delta Petroleum case in Mesa County where a blowout preventer failed and had to be replaced, although the well was kept in control. That same year, he said, a preventer couldn’t stop a gas blowout at an Antero Resources well because it apparently closed on a pipe joint, which kept it from closing correctly.
In a 2006 Garfield County case, a preventer had to be replaced after being deployed and possibly worn down by blasting sand particles while a crew held off until daylight to circulate mud, Ellsworth said. He said mud circulation is key to dealing with well-control issues. Ideally, drilling crews monitor for pressure problems and pump heavier drilling mud down a well if needed to keep it in control.
In a 2008 blowout at a Williams well, rig crews didn’t respond in time to a gas “kick” that came on quickly, he said. Because they had a drive mechanism down the well, they couldn’t close the blowout preventer. Gas ignited, burning the drilling rig.
In 2004, the state fined Williams $30,000 for violations including failing to report a gas kick and do proper testing of a well that ended up having a blowout and fire. The state found that uncontrolled venting of gas endangered workers and the public.
The Antero blowout led to nearby residents being put on evacuation notice, but emergency crews deemed gas levels safe for them to remain in their homes.
Antero said the gas rose into the atmosphere and dispersed, but environmental and citizen groups voiced concern about the potential for health impacts on area residents.
State oil and gas commissioner Tresi Houpt, also a Garfield County commissioner, said last week the commission has heard past testimony of someone’s health being affected by a well fire.
She said it raises the question of whether drilling areas with known high-pressure situations should be a consideration in what setbacks are required between well pads and homes.