What Does Well Control Mean?
Well control is used in oil and gas drilling to maintain pressure on open formation and minimize the influx of formation fluid (kick) into the wellbore. To prevent kicks, weighting agents are added to the drilling mud to maintain sufficient bottomhole pressure (BHP). When kicks are not managed properly, it can result in a blowout event, which can be catastrophic to life, property, and the environment.
Safeopedia Explains Well Control
Drilling for oil and gas requires the drilling of wellbores deep beneath the earth's surface to reduce the likelihood of a sudden and dangerous release of pressure. Well control minimizes some of the risks associated with those wellbores.
Types of Well Control
There are three types of well control:
- Primary well control, which maintains hydrostatic pressure heavy enough to overcome formation pressure without fracturing formation
- Secondary well control, which uses blowout preventers (BOPs) when primary well control is lost
- Tertiary well control, which uses special methods such as relief wells, dynamic kill, barite, or cement pumping to plug the wellbore if other methods fail
Warning Signs of a Kick
A kick can occur due to various reasons, such as insufficient mud weight, improper mud replacement during trips, swabbing, and lost circulation. Workers should be made aware of the common warning signs.
Primary indicators of a kick include:
- An increase in the flow rate of drilling fluid
- An increase in the volume of mud in the mud pit
- Continued flow of drilling fluid returns even after mud pumps are turned off
- Improper volume balance in the mud pit on the removal of drill pipe from the wellbore
While secondary indicators include:
- An increase in pump stroke but a decrease in pump pressure
- Change in the apparent weight-on bit
- Drill break (a sudden change in the rate of drill penetration) or bit drop (a sudden increase in drill bit depth)
- Loss of mud weight
Managing Well Control Situations
There are two basic components involved in well control: active and passive. The active component involves monitoring the drilling fluid pressure, while the passive component includes blowout preventers.
The activities involved in well control are:
- Program for blowout prevention
- Mud system monitoring and maintenance
- Installation and testing of BOPs, accumulator, and choke manifold
- Maintaining surface control system
Well control activities require skilled and well-trained individuals; however, well control situations are often caused by factors outside their direct control. It is necessary to establish and follow a complete well engineering management system to ensure:
- Comprehensive basis of design document
- Detailed drilling program and instructions
- Preventive well control measures
- Proper training of personnel to enhance competency