Liu Shuangquan

A High-Efficiency Plunger Gas Lift Drainage Technology in Horizontal Wells

At present, the Changqing gas zone has more than 1300 gas wells in all and effusion problem emerges gradually. Plunger gas lift technology has become the main technology of drainage gas recovery technique of Changqing gas field in Erdos basin area. But the horizontal well tubing in Changqing gas field reduces before entering into the horizontal section, so the plunger cannot pass and the bottom effusion could not be lifted. Moreover, since the locking device of the existing plunger device in high angle-deviated area is difficult to fix, this technique can only be applied to vertical wells and cannot be used in horizontal wells with high angle-deviated wellbore trajectory. Therefore, in order to use plunger gas lift technology to lift total wellbore fluid in horizontal wells, a high-efficiency plunger gas lift drainage technology used in horizontal wells is designed. A self-buffer plunger and a single-flow device realize the relay of lifting discharge: The single-flow device is placed in the necking position which allows gas wells to rely on their own energy to lift wellbore fluid up over the single-flow device, and the self-buffer plunger lifts the liquid from this position to the wellhead. Taking into consideration the structure features of horizontal wells, the integration of plunger and the downhole tool structure, impact test, and so on, a self-buffer plunger is designed. The new design not only increases the depth but also simplifies the downhole tool of the existing plunger device. By using the heat expansion principle of rubber and one-way flow valve, a single-flow device with a simple structure, easy to use, easy to salvage, is designed which makes the gas–liquid flow in one direction. Under test conditions, the self-buffer plunger and single-flow device can meet the requirement of safe operation; ensure the plunger landing impact without damaging the tube and plunger body and good performance in positioning and one-way flow of the single-flow device. Having been successfully applied in Changqing gas field, this high-efficiency plunger gas lift drainage technology in horizontal wells can lift the whole horizontal well wellbore fluid, greatly reduce the shaft height of liquid column, and increase gas production. Therefore, its application effect is remarkable and can solve the problem of drainage gas recovery in horizontal wells.