Abstract: The invention generally relates to a plunger lift system that can be used in all type of oil and gas wells including wells of vertical, highly deviated, S-curved or horizontal bores. The plunger lift system has a ball-shaped plunger. Multiple ball plungers may be used for a single operation to lift liquid out of a wellbore. Certain embodiments further include a surface lubricator, associated piping and valve systems in communication with a pipeline, a surface control system and related equipment, a downhole bumper spring assembly and/or retrieval device having a magnet to retrieve the ball plunger of the wellbore if and when needed. The invention also relates to ball-shaped plungers and to methods for lifting liquid out of a wellbore employing such ball-shaped plunger. In certain embodiments, the ball plunger comprises a hole or a plurality of holes to aerate the fluid load.

Abstract: An improved free piston assembly for use in combination with a plunger lift assembly is provided. The improved free piston assembly includes a sleeve member, a flow restriction member, and retention means. In some embodiments of the invention the sleeve member has an inner surface that is contoured to provide a seat for the flow restriction member during lifting operations. The flow restriction member can be a ball held in the interior of the sleeve by retention means capable of overcoming the force of gravity but at the same time designed to release the flow restriction member when a rod of the plunger lift assembly contacts the flow restriction member. In one embodiment of the invention the retention means is a plurality of inwardly biased spring loaded held in place by a retention ring that is fittably received by a groove in the exterior surface of the sleeve. In other embodiments of the invention the retention means are in the form of a raised lip or a retention sleeve.

Abstract: The invention generally relates to a plunger lift system that can be used in all type of oil and gas wells including wells of vertical, highly deviated, S-curved or horizontal bores. The plunger lift system has a ball-shaped plunger. Multiple ball plungers may be used for a single operation to lift liquid out of a wellbore. Certain embodiments further include a surface lubricator, associated piping and valve systems in communication with a pipeline, a surface control system and related equipment, a downhole bumper spring assembly and/or retrieval device having a magnet to retrieve the ball plunger of the wellbore if and when needed. The invention also relates to ball-shaped plungers and to methods for lifting liquid out of a wellbore employing such ball-shaped plunger. In certain embodiments, the ball plunger comprises a hole or a plurality of holes to aerate the fluid load.