... pressure during drilling to prevent well blowout effectively and realize safe Annular BOP is an important part ... of rubber if there is adrilling tool, tubing or casing in hole.2, When there is no ... well head completely. 3, When the well blowout and overflow happens during drilling, coring or welllogging, it ... spaces between Kelly, coring tools, cable,wire line and well bore.4, Under the control of the ...