Oil & Gas Drill String Valves (IBOPs)
Drill String Valves stop fluids from flowing up the drill string. Often if the well kicks with a bit of bottom, formation fluids flow up the annulus and up the drill string. Crew members close the drill string valves to stop the flow in the string. If the Kelly is made up, they can close the upper or lower Kelly Cock. If the Kelly is not made up then they can install the full opening safety valve in the top of the drill string.
An Inside Blowout Preventer or IBOP is a one-way valve, a check valve leaked and installed in the drill string. One type of IBOP is a Float Valve that is sometimes made up in the drill string near the bit. It prevents the backflow up the drill string. Another type of IBOP is the Drop-In Valve or D.I.V, it’s dropped into the drill string in falls to a special landing Sub that is usually located near the top drill collar in the drill stem. It allows the driller to pump mud down the string but the check valve will not allow influx fluid to flow up the string.
Another type of Inside BOP is the Heavy Duty Check Valve or great type valve after one company that makes it. It’s a plunger check valve that crew stab in the drill pipe at the surface. It’s usually used during stripping operations. Stripping is when the crew lowers the pipe in the whole, while the BOPs are closed and under pressure.
Upper/Lower Kelly Cock
An Upper Kelly Cock is located above the Kelly. The Upper Kelly Cock normally serves as a backup to the lower Kelly Cock. If the Lower Kelly Cock failed, crew members would use a special operating wrench to close the Upper Kelly Cock. The closed Upper Kelly Cock prevents further flow, it protects the equipment above the Kelly from high pressure flow. Usually crew members close the Lower Kelly Cock. If a kick puts risk on the equipment above the Kelly, they make it up in the bottom of the Kelly. A crew member uses a special operating wrench to close it. The crew can also close the lower Kelly Cock to keep mud from falling out of the Kelly when they break after a Kelly to make a connection.
Full-Opening Safety Valve
If the Kelly is not made up in the drill string and flow occurs, crew members can insert the safety valve in the drill string. This procedure is called Stabbing of full opening valve as a large in inside opening as possible. When fully open, flow from the drill pipe passes through the valve with no additional restriction. This relatively large opening allows the crew to stab the valve against pressure coming out of the drill string.
Safety Valve Usage
The crew pick up a safety valve by its lifting handles. They make sure it is fully open and stab it into the drill pipe, then they screw it into the pipe. Finally, they use a special operating wrench to close the valve and shut off flow.
Driller should make sure the rig has the right crossover subs handy on the rig floor. Crew members should be able to make up the safety valve in any drill string member coming out of the rotary. For example, if a drill collar is in the rotary, the safety valve’s threads may not match the drill collar’s threads. They will need the right cross over Sub to make it work.
Float Valves
Float valves also prevent flow up the drill string. Crew members place a float valve in a Sub, a special drill string fitting just above the bit. One type allow mud to be pumped down. But shuts against upward flow under normal conditions. Pump pressure moves drilling mud through the open one way valve. An influx of formation fluid from bellow causes the float valve to close, this prevents further flow up the drill string.
