What is the main function of the blowout preventer?

In oil and gas drilling construction, in order to safely drill through high-pressure oil and gas layers and avoid out-of-control drilling blowout accidents, a set of equipment – a drilling well control device – needs to be installed on the wellhead of the drilling well. When the pressure in the wellbore is less than the formation pressure, oil, gas, and water in the underground formation enter the wellbore and form overflow or kick. In serious cases, drilling blowout and fire accidents may occur. The function of the drilling well control device is to quickly and promptly close the wellhead when overflow or kick occurs in the well to prevent blowout accidents.

Drilling well control devices mainly include: blowout preventer, spool, remote control console, driller’s console, choke and kill manifold, etc. The drilling well control device meets the requirements of drilling technology, is easy to operate, and can quickly close and open the wellhead. It can be controlled on the driller’s console of the drilling rig or on a remote console far away from the wellhead. The device must have a certain pressure resistance and can realize controlled blowout, well killing and tripping of drilling tools. After installing the rotating blowout preventer, drilling operations can be carried out without killing the well.

Drilling BOPs can generally be divided into single ram, double ram, (annular) and rotating BOPs. According to the requirements of the formation being drilled and the drilling technology, several blowout preventers can also be used in combination at the same time. There are 15 sizes of existing drilling BOPs. The size selection depends on the casing size in the drilling design, that is, the nominal diameter size of the drilling BOP is slightly larger than the outer diameter of the casing coupling that is run again. The pressure of the blowout preventer ranges from 3.5 to 175 MPa, with a total of 9 pressure levels. The selection principle is determined by the maximum wellhead pressure endured when shutting in the well.