Classification and selection of blowout preventer

The most important equipment to understand the performance of well control equipment, correctly install and maintain, and make the well control equipment play its due function is the blowout preventer. There are two kinds of common blowout preventers: ring blowout preventer and ram blowout preventer.

1.Ring preventer

(1) When there is a pipe string in the well, a rubber core can be used to close the annular space formed by the pipe string and the wellhead;

(2) The well head can be fully sealed when the well is empty;

(3) In the process of drilling and milling, casing grinding, logging and fishing down, in case of overflow or blowout, it can seal the space formed by kelly pipe, cable, wire rope, accident handling tools and wellhead;

(4) With the pressure relief regulator or small energy storage, it can force the butt welded pipe joint without fine buckle at 18°;

(5) In case of serious overflow or blowout, it is used to achieve soft shut-in with ram BOP and throttle manifold.

2.Ram blowout preventer

(1) When there are drilling tools in the well, the half-sealed ram corresponding to the size of the drilling tool can be used to close the ring space of the wellhead;

(2) When there is no drilling tool in the well, the full sealing ram can fully seal the wellhead;

(3) When it is necessary to cut the drilling tool in the well and completely seal the wellhead, the shear ram can be used to cut the drilling tool in the well and completely seal the wellhead;

(4) The ram of some ram blowout preventers allows load bearing and can be used to suspend drilling tools;

(5) There is a side hole on the shell of the ram BOP, which can use the side hole throttling pressure relief;

(6) Ram BOP can be used for long-term well sealing;

3.Selection of BOP combinations

The main factors to be considered in the selection of hydraulic blowout preventer combination are: well type, formation pressure, casing size, formation fluid type, climate impact, environmental protection requirements, etc.

(1) The choice of pressure level

It is mainly determined by the maximum wellhead pressure that the BOP combination is expected to withstand. There are five pressure levels of the BOP: 14MPa, 21MPa, 35MPa, 70MPa, 105MPa, 140MPa.

(2) Path selection

The diameter of the BOP combination depends on the casing size in the well structure design, that is, it must be slightly larger than the outer diameter of the casing to which it is attached. There are nine kinds of blowout preventer diameters: 180mm, 230mm, 280mm, 346mm, 426mm, 476mm, 528mm, 540mm, 680mm. Among them, 230mm, 280mm, 346mm and 540mm are commonly used in the field.

(3) Choice of combination form

The selection of combination form is mainly based on formation pressure, drilling process requirements, drilling tool structure and equipment supporting conditions.