Use of Adjustable Chokes to Prevent Offshore Injuries
Offshore oil and gas exploration is a lucrative business, but it also carries a number of unique hazards. Often, one wrong move or defective machine part can have a devastating impact on extraction efforts. With the ever-increasing race to extract minerals, the energy industry has unfortunately had to deal with several massive catastrophes.
The blowout preventer (BOP) was cited as a major cause of that deadly blast and the subsequent massive oil spill. The BOP consists of giant sets of valves that are supposed to seal off an oil well in an emergency. In the Deepwater Horizon explosion, the pipe running from the subsea oil well to the drilling rig through the BOP buckled around the time a surge of natural gas from the well ignited and caused the explosion. The leading factor was the inability to reduce pressure inside the pipes.
A choke manifold is an arrangement of piping and special valves, called chokes. Drilling mud is circulated through these chokes when the blowout preventers are closed, so that pressure can be controlled during kicks. When a kick occurs, the drilling mud is redirected from the wellbore to the choke manifold using a choke valve.
(For readers unfamiliar with drilling, a “well kick” is when the pressure within the rock is greater than the mud pressure of the pipe—this forces fluid upwards into the wellbore).
The Layman’s Explanation
Offshore drilling is a matter of managing pressure. Crews are dealing with thousands of pounds of pressure per inch with a variety of fluids, including mud, oil, and water. Choke valves relieve pressure when the pressure within the drilling system gets dangerously high. It provides extra space for the fluid to travel, dissipating the force quickly.
To borrow an everyday image, imagine you’re drinking soda through a straw. By drinking as quickly as possible, you’re applying a great deal of pressure inside the straw (which is free-flowing, so it’s not an issue). Now imagine poking holes in the straw as you drink. The holes lessens pressure inside the straw because the soda has extra space to travel.
Adjustable choke valves create the extra space drilling crews need to control pressure as needed.
What Is an Adjustable Choke?
A choke valve is designed to reduce the flow of a fluid. Adjustable chokes are used to control the flow by opening or closing the valves. To withstand highly erosive and corrosive substances, they are typically made with tungsten carbide or Inconel.
Adjustable chokes can be manually or hydraulically operated to adjust the flow and pressure of oil. One particular design involves a choke valve that uses a cylinder to plug holes or slots in another cylinder by raising or lowering it in or around the second cylinder. This allows the choke valve to help dissipate energy through a process known as "flow impingement."
Preventing Offshore Catastrophes
The use of choke valves is crucial to preventing catastrophic blowouts that can injure or kill offshore workers. Offshore drilling is an inherently dangerous activity, but many of those risks can be engineered out with preventive equipment such as choke valves. If an accident occurs offshore and the owner or operator of the well did not take the necessary precautions to help prevent the accident, they could be held liable for an injuries suffered by workers.
If you have been injured in an offshore accident, consult with an experienced maritime lawyer to learn about your legal rights. Contact Arnold & Itkin today for a free case evaluation.