唐山地区干热岩埋钻、断钻事故处理技术研究OA

For a hot dry rock(HDR)project in Tangshan,the designed well depth is 4000 m,and the planned drilling progress was to reach 2800 m by 2022,targeting the Archean stratum.However,the actual drilled strata exposed during drilling deviated significantly from the designed ones,resulting in an excessively long open-hole interval.During the construction period,total lost circulation occurred,which triggered drilling accidents such as buried drill bit and broken drilling rod.In this paper,it is analyzed that the cause of buried drill bit is the unreasonable design of wellbore structure,where non-circulating lost circulation leads to the imbalance of formation pressure and collapse of borehole wall.During the casing milling operation,improper torque control and inherent structural weaknesses in 127 mm anti thread drilling tool resulted in twisting accident,further complicating accident treatment.To address these issues,blasting loosening and side drilling were successfully implemented during accident handling process,therefore avoiding accident further complexity,shortening accident handling time and reducing losses,which has certain reference significance for the design of wellbore structures,accident prevention and handling in similar projects.