Development and Application of Auxiliary Equipment in Wellhead for Small Tubing Plunger Lift

With the development of tight gas reservoirs, production decline due to liquid loading in gas wells has become increasingly prominent. Conventional plunger lift operations often suffer from low lifting efficiency and operational instability, particularly due to the mismatch between the internal diameter of the Christmas tree and the tubing string. This discrepancy can prevent the plunger from reaching the lubricator, causing issues such as plunger oscillation, gas channeling, and liquid fallback within the Christmas tree, as well as the inability of the wellhead sensors to detect the plunger's operating cycle. To address these challenges, this study proposes and develops a novel wellhead auxiliary equipment/tool—the plunger barrel designed to stabilize plunger movement and assist the plunger in reaching the lubricator. Through theoretical analysis, numerical simulation, and field testing, this study systematically investigates the structural optimization and process adaptability of the plunger barrel. A collision dynamics model was established based on the conservation of energy and momentum equations to analyze the interaction between the plunger and the plunger barrel. This model elucidates the mechanisms of dynamic engagement, synchronized upward movement, and restricted stagnation. Furthermore, a critical pressure differential criterion was derived to provide theoretical guidance for optimizing operational parameters. Field applications have confirmed the effectiveness of the equipment: following installation of the plunger barrel in Well of the Lingxing Block, the increased success rate of the plunger reaching the lubricator, along with an extended afterflow period, has improved the plunger operating cycle and well productivity.