Development and Application of a Hydraulic Control-Type Safety Annulus Packer for Water Injectors in Offshore Oilfields

Without flushing channels,the conventional annular-safe packers used in the Chengdao Oilfield can hardly satisfy demands for adequate oilfield development.By analyzing the annular-safe tools in China and around the world,the hydraulic annular-safe packer with two independent hydraulic channels (for control over flushing and seating devices,respectively) has been developed.The hydraulic system in the top section of the packer can be used to control the over flushing devices:and flushing operations can be initialized under control of hydraulic pressure.Upon pressure release in hydraulic control pipelines,dual springs can be initialized to control the slip sleeve and close the system.The hydraulic system in the central part is connected with that in lower parts.Jointly,they may control the simultaneous seating of packer and the packer for layered injection in reservoir sections of the pipe string;The innovative packer is equipped with locking mechanism for seating.Under emergency conditions,the rubber barrel may not retract even in circumstances with accidental pressure releasing.In this way,the annular safety can be guaranteed.Upon successful development of the hydraulic annular-safe packer,calculation model for stresses on pipe string in 3D wellbore have been used to determine tensile strength of the central pipe in accordance with setting depths of annular-safe tools.During this research,the performance of the new hydraulic annular-safe packer has been reviewed prior to the application in 42 water injectors on site.Field application performances show that properly seated slip sleeves can effectively maintain casing pressure at 0 MPa after multiple flushing operations.Generally speaking,the innovative packer can provide effective protection over marine environments.Research results show that this hydraulic annular-safe packer can effectively solve problems in existing annular-safe packers in the Chengdao Oilfield.In addition,the newly-developed packer can satisfy demands for development of other offshore oilfields in safe and environment-friendly manner.