BASIC BOP EQUIPMENT PRESSURE CONTROL

BASIC BOP EQUIPMENT
PRESSURE CONTROL

Overview:

Fluids in the formation are under pressure. When drilled, this pressure can escape to the surface if it is not controlled. Normally drilling mud offsets formation pressure, that is the weight or pressure of the drilling mud keeps fluid in the formation from coming to the surface. For several reasons however, the mud weight can become lighter than it’s necessary to offset the pressure in the formation. When this situation occurs, formation fluids enter the hole. When formation fluids enter the hole, this is called a “kick”. A blowout preventer stack is used to keep formation fluids from coming to the surface. These are called “BOP”s. By closing a valve in this equipment, the rig crew can seal off the hole. Sealing the hole prevents more formation fluids from entering the hole. With the well sealed or shut in, the well is under control. Rig crews use a surface BOP system on land rigs, jack-up rigs, submersible rigs and platform rigs. They use a subsea BOP system on offshore floating rigs, like semi-submersibles and drill ships.

[TOOL BOX]: Why do you suppose subsea BOP system are used on semi-submersibles and drill ships? Blowout prevention equipment is very large and very heavy. Semi-submersibles and drill ships are dynamic, that is they float and thus move with wind & waves while in working mode. On floating rigs, it is not practical to mount the BOP stack on top of the long riser pipe. The BOP stack is much too heavy for the relatively thin and flexible walls of the riser pipe. Also because the riser walls are relatively thin, they cannot withstand the high pressures that could develop inside the riser when the well’s shut in on a kick. So the rig crew mounts the BOP stack on the well head at the see floor and makes up the riser on top of the stack.

Blowout

A blow out is dangerous. Formation fluids like gas and oil blow to the surface and burn. Blow outs can injure or kill, destroy the rig, and harm the environment. Rig crews there for trained and work hard to prevent blowouts. Usually they’re successful, so blowouts are rare. But when they happen, they are spectacular and thus often make new