Well Control Safety
Properly trained personnel are essential for well control activities. Well control consists of two basic components:
- an active component consisting of drilling fluid pressure monitoring activities, and
- a passive component consisting of the Blowout Preventers (BOPs).
The activities involved in well control are:
- blowout prevention program
- monitoring and maintaining mud system
- testing BOPs, accumulators, and choke manifold
- maintaining surface control system
Now, let’s take a closer look at these specific activities on the drilling site.
Blowout Prevention Program
The first line of defense in well control is to have sufficient drilling fluid pressure in the well hole. During drilling, underground fluids such as gas, water, or oil under pressure (the formation pressure) opposes the drilling fluid pressure (mud pressure). If the formation pressure is greater than the mud pressure, there is the possibility of a blowout.
Potential Hazards:
- receiving injuries caused by loss of well control
Possible Solutions:
- Appropriate training for tasks performed. Example topics include the following:
- causes of kicks, including detection
- pressure concepts and calculations
- well control procedures
- gas characteristics and behavior
- fluids
- constant bottom hole pressure well control methods
- well control equipment
- regulatory information
- Use of appropriate well control equipment including:
- specification
- installation
- maintenance
Monitoring and Maintaining Mud System
The mud circulatory system consists of the several elements. Let's take a closer look.
Schematic of the circulating system: The drill bit, drill collar, annulus, drill pipe, kelly and swivel are depicted in the upper right. Drilling mud flows through the mud return line upon its return to the surface from the hole to the shale shaker, then to the adjacent desander, desilter and degasser back to the mud tank. Mud passes through the suction line, and the mud pump circulates the mud through the discharge line, the stand pipe through the rotary hose and the swivel, back to the kelly and into the drill pipe.
Each part of this system must function and be in good repair to maintain well control.
If the mud level increases, it may be a sign that a kick is in progress. A kick is an entry of water, gas, oil, or other formation fluid into the wellbore during drilling. It occurs because the pressure exerted by the column of drilling fluid is not great enough to overcome the pressure exerted by the fluids in the formation drilled. If prompt action is not taken to control the kick, or kill the well, a blowout may occur.
On some rigs there is a mud float level gage which sounds an automatic alarm if the mud exceeds a pre-specified level.
Potential Hazards:
- loss of well control (blowout)
Possible Solutions:
- Keep the mud circulating system in good working order.
- Check and maintain the properties of the drilling fluid, including proper pit level periodically.
- Properly train crew in monitoring and well control procedures.
- Maintain a properly functioning surface control system.
Installing and Testing BOPs, Accumulator, and Choke Manifold
In the well control system installation process, the blowout preventer (BOP), accumulator and choke manifold are installed by the rig crew after the surface casing is set and cemented.
The BOP is one or more valves installed at the wellhead to prevent the escape of pressure either in the annular space between the casing and the drill pipe or in open hole (for example, hole with no drill pipe) during drilling or completion operations.
The accumulator and choke manifold have been set into place during rigging up and now need to be hooked up and tested.
The accumulator is a storage device for nitrogen pressurized hydraulic fluid, which is used in operating the blowout preventers.
The choke manifold is the arrangement of piping and special valves, called chokes, through which drilling mud is circulated when the blowout preventers are closed to control the pressures encountered during a kick.
- The choke line valve is used to redirect the mud from the well bore to the choke manifold during a kick.
- The kill line valve is used to direct drilling fluid to the BOP during a kick.
The BOPs, accumulators, and choke manifold should be regularly tested and properly maintained.
We will discuss the potential hazards and possible solutions in the next tab.
Installing and Testing BOPs, Accumulator, and Choke Manifold (Continued)
Potential Hazards:
- being crushed by falling equipment if hoisting slings fail
- being struck by, pinched by or caught between equipment during installation
- being hit by hoses or sprayed by hydraulic fluid if there is a seal or hydraulic line failure during pressure testing
Possible Solutions:
- Ensure workers stand clear of equipment being hoisted and tag lines are used where appropriate.
- Coordinate hoisting tasks with rig crew.
- Inspect the hoisting slings for wear before any hoisting operation.
- Ensure all personnel wear proper PPE.
- Ensure workers stand clear of pressurized lines during testing procedures.
Maintaining Surface Control System
Properly maintain the surface control system.
Potential Hazards:
- protruding pipes and objects
- being struck by dropped objects
- slips, trips, and falls
- atmospheric hazards
Possible Solutions:
- Wear appropriate personal protective equipment (such as hard hats, work gloves, safety shoes, and eye protection).
- Implement injury awareness training (such as dropped objects, working from heights)
- Use appropriate fall protection.
- Ensure workers are aware of the slipping and falling hazards.
- Monitor for potential hazards (H2S, methane, O2 deficiency).
Video
This is a USCSB training video for the onshore drilling industry detailing lessons learned from the January 22, 2018, blowout and fire at the Pryor Trust gas well in Pittsburg County, Oklahoma, that fatally injured five workers.
Instructions
Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.
Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.