Blowout preventer is used to test well, workover, completion and other operations shut down the wellhead to prevent the blowout occurred, the full seal and semi-sealed two functions together, with the structure is simple, easy to operate, high pressure and so on , Is commonly used in the oil field to prevent blowout safety seal wellhead device.

Oil drilling, installed in the wellhead casing head, used to control high-pressure oil, gas and water blowout device. BOP shut down (shut-off) the wellbore when the pressure in the well is high. Pressure from the drill pipe into the heavy mud, there are four under the gate, can replace the invasion by the invasion of mud, increasing the pressure of liquid column to suppress the high-pressure oil and gas jet.

Blowout preventer its type sub-BOP, universal BOP and rotary BOP. Universal blowout preventer is able to start in case of emergency, to deal with any size drill and empty well; rotary blowout preventer is able to achieve side edge drilling operations. In deep well drilling is often in addition to two kinds of ordinary blowout preventer, plus universal blowout preventer, rotary blowout preventer.

Annular BOPs are often equipped with large gates for ram blowout preventers that, when in operation, form a sealed annular space between the tubing string and the wellbore and, in the case of a column within the well, can complete the well seal alone, but With a few times it will not work BOP, BOP function and does not allow long-term shut-in use.