As hydrocarbon wells mature, they exhibit a decrease in bottom-hole pressures and the production velocities, which are necessary to carry fluids—e.g., produced water, oil and condensate—to the surface. Over time, these fluids can accumulate in the downhole production tubing, resulting in a condition known as liquid loading. Toward the end of the production life of the hydrocarbon well, as formation fluid accumulates at the bottom of the wellbore, the liquid loading may reach a level that interferes with the well's performance. In particular, the well loses energy as the reservoir's natural pressure is countered by the hydrostatic head created by the accumulated fluid. The lost energy in the well necessitates employing measures to lift the formation fluid to the surface to prevent the liquid-loading condition from killing the well. Several techniques exist for artificially lifting formation fluids, including plunger lift systems. Plunger lift systems attempt to remove fluids from the wellbore so that the well can be produced at the lowest bottom-hole pressure and maximum rate by harnessing the well's own energy to remove the accumulated fluids and sustain gas production. Conventional plunger lift systems rely on a piston dropped into a flowing or non-flowing wellbore. A bumper spring at the bottom of the well cushions the impact of the piston. Gas flowing into the well below the piston pushes the piston upward, thereby pushing any formation fluid toward the surface. These pistons—e.g., pad, solid, bypass, and brush plungers, etc.—may have fluid fallback due to insufficient sealing with the tubing/casing wall.
There are problems with using conventional tubular-shaped plungers in deviated and vertical wells. Such plungers may not have a sufficient seal, thereby causing undesirable fluid fallback to occur. Typical sealing devices are constructed from steel and/or fibers. These seals fail over time. The lack of seal may allow the well to liquid load over time because of fluid fallback. Liquid loading occurs when the hydrostatic pressure of the fluid is greater than the gas pressure below, restricting gas from surfacing through the surface equipment. The conventional tubing coupling collar used in the industry has a gap between each tubing joint. This gap in the inside diameter of the tubing allows fluid to be trapped at each connection and is an obstruction to making contact between the plunger and seal. Contact with artificial lift tools and this tubing/collar gap will cause premature wear, breakage, and fluid fallback.
Thus, there is a need for a plunger lift system that reduces fluid fallback and more efficiently lifts formation fluid to the surface.