:: Blowout Prevention
by Steve Vorenkamp and Bill Mahler, Wild Well Control
Today, blowouts occur at a rate of nearly one in one-thousand wells drilled or operated. Unfortunately, this rate appears to remain roughly constant year after year. A blowout is the most catastrophic event that can occur during a drilling or workover operation. However, virtually all blowouts are preventable.
A blowout can take many forms including a massive fireball that engulfs a rig. Even if there is no fire, a blowout wastes the valuable petroleum or gas expelled.
Leading Causes of Incidents
The first stage of a well-control incident is when oil, gas, or water from the formation enters the wellbore. This is known as a kick. If not controlled, a kick can intensify. The fluid or gas entering the wellbore displaces an equal volume of drilling mud. Loss of that dense drilling mud reduces the fluid pressure within the wellbore, allowing more formation fluid to flow into the well. That, in turn, reduces the wellbore pressure even further, and so on. If this vicious cycle is not broken quickly, it can accelerate into a blowout powerful enough to eject the drill string from the well, damage the rig, and, in some cases, create a plume of gas or oil that can be easily ignited.
The two leading causes of kicks are poor drilling practices and equipment failures. Poor practices include not maintaining the drilling fluid at the correct density or fluid level, not waiting long enough for cement casing to set, and tripping pipe too fast, causing fluctuations of hydrostatic pressure called “surging” or “swabbing.” Poor practices also include failure to detect and manage a kick when one does occur. Equipment failures can also occur during drilling or completion operations. They are a particular problem in high-pressure frac operations such as those done in the Bakken and Marcellus shales.
Preventing an Event
Responsible operators, drilling contractors, and well workover and servicing companies must take preventive action to mitigate the risks and maximize the chance of bringing the well back under control. To do this, computer software is used to model kick behavior using the expected parameters for a particular well before drilling begins and again with updated data during drilling. The well-control equipment on a rig is carefully inspected and tested regularly. Operators and rig personnel are put through well-control training programs so they can spot the signs of a kick and react correctly. These training courses must be practical and tailored to the type of well the crew will be drilling. Frequent emergency drills—realistic and unannounced—will build a crew’s readiness to handle a real crisis. Practical, straightforward emergency response plans should be prepared and ready for quick use. Finally, if conventional well-control methods do not work, personnel on the rig should be prepared to call in well-control specialists.
It is crucial that operators, drilling contractors, and well servicing companies understand the risks posed by blowouts. Once acknowledged, these risks can be addressed and mitigated through policies and preventive measures, the most important of which is thorough training.
Steve Vorenkamp is General Manager of Training and Bill Mahler is Executive Vice President and General Manager of Wild Well Control Inc., a leading provider of firefighting, well control, engineering, and training services based in Houston, Texas. Wild Well supports PETEX in delivering quality training on well control issues. Vorenkamp is a long-time and popular instructor of well control operations at the PETEX Houston Training Center.