Application of Hard-Top Well Killing Technology in Bohai Oilfield
[Purposes]The geological and downhole conditions faced by offshore oilfield drilling opera-tions are becoming increasingly complex,and some wells cannot be killed using conventional well killing methods,which not only increases the operation period,but also may create well control risks.In order to achieve safe well killing of complex wells in Bohai Oilfield and avoid well control accidents,the hard top well killing technology has been applied in Bohai Oilfield.[Methods]The applicable working conditions of hard top well killing technology were analyzed in response to the special working conditions of Bohai Oilfield.The relevant calculation principles of hard top well killing technology were pointed out.By ana-lyzing the application examples of hard top well killing technology,the precautions for the application of this technology were proposed.[Findings]The results indicate that the hard-top method of well killing technology is suitable for five aspects:the shut in drill bit is far from the bottom of the well,the formation contains toxic and harmful gases,the drilling tool or drill bit is blocked in the water hole,the leakage oc-curs after the well is shut in,and the well is killed after long open hole testing.The calculation principles can be considered from three aspects:the calculation of well killing fluid density,the selection of well killing displacement,and process calculation.Based on the application example of this technology in Well A of Bohai Oilfield,four aspects that need to be noted are proposed:determining and clarifying the pressure resistance level of key equipment at the wellhead,determining the pressure bearing capacity of the formation at the upper casing shoe,selecting equipment,and handling weak formations.[Conclu-sions]The research results clarify the principles and precautions for the use of hard top well killing tech-nology,providing technical support and reference for the application of hard top well killing technology in complex offshore oil fields.