Research On The Mechanical And Arc Compound Cutting Technology And Cutting Equipment For The Abandoned Offshore Platform Wellhead

The development of Chinese offshore petroleum industry started late but developed rapidly,more and more abandoned offshore platform wellhead will be abandoned in the following years.According to the related laws,abandoned offshore platform wellhead must be cut and recovered within 5m below the seabed mud line.However the wellhead removal technology fall behind the foreign counties in China,therefore to develop a highly efficient and reliable wellhead recovery technology has an important theoretical and engineering application value.The paper has a systematic and thorough research for the abandoned offshore platform wellhead cutting and recovering technology,and get a series of innovative achievements.Advance a new method which is using the mechanical and arc compound cutting technology to cut and recovery the abandoned offshore platform wellhead.The compound cutting technology combines the advantage of mechanical and arc cutting.Mechanical cutting is mainly used to cut the non-conductive deposits sticking on the casing surface,arc is used for metal casing cutting.Combined with mechanical and arc cutting can better solve the problem of large cutting force,serious vibration,low cutting efficient,great tool wear and high cost for the traditional technologies.And avoid the problem that non-conductive deposits cannot be cut by arc.The technology can achieve highly efficient and stable cutting effect.A mechanical and arc compound cutting tool prototype for 9⁵/₈in casing is developed.The cutting tool consists of the upper centralizer,the rotation mechanism,the lower centralizer,compound cutting mechanism and cutting blades auto changing mechanism.The motors used in the cutting equipment are sealed by filling grease which can well solve the underwater motors sealing issue.The cutting blades auto changing mechanism can automatic replace the worn cutting blades,it can reduce the operating costs and make the cutting operation more efficient.Developed an abandoned offshore platform wellhead mechanical and arc compound cutting equipment control system is developed.The control system mainly includes underwater control box,underwater power modules and upper water PC.An interactive interface is developed,it consists of six major parts:serial configuration,manual control,real-time monitoring,data management and system settings.The user can conveniently monitor and control the cutting equipment by operating the interface.Developed a casing cutting and recovering simulation device.The device consists of cutting frame,winch lifting mechanism,casing,cutting equipment and cutting control system.Studied the process parameters about the mechanical and arc compound cutting.Reveal the influents on the cutting result with different cutting blades rotation,the materials of the cutting blades,whether using arc cutting,arc current and high voltage.Obtained the efficient and stable cutting parameters.