Plunger Lifts and their Applications
A plunger-lift system is a low-cost, efficient method of increasing and optimizing production in oil and gas wells, which have marginal flow characteristics.
Functionally, it provides a mechanical interface between the produced liquids and gas. Using the well's own energy for lift, liquids are pushed to the surface by the movement of a free-traveling piston (plunger) traveling from the bottom of the well to the surface. This mechanical interface eliminates liquid fallback, thus boosting the well's lifting efficiency. In turn, the reduction of average flowing bottomhole pressure increases inflow.
Eliminates liquid loading. As production velocity drops, wells tend to be less efficient in carrying their own liquids to the surface. The introduction of a plunger in this type well re-establishes the original production decline curve, increasing the economic life of the well. At the same time, it generally reduces the volume of injection gas required.
High Ratio Oil Wells
Increases the economic life of this type well. By producing the well in an intermittent fashion, the wells own energy can be used. The need for other, more costly, lifting options can be eliminated.
Intermittent Gas Lift Wells
Most intermittent gas-lift wells suffer from liquid fallback. This fallback tends to increase the average flowing bottomhole pressure, thus reducing production. With the plunger serving as a mechanical interface, liquids cannot fall back, but are all brought to the surface.
Paraffin and Hydrate Control
Most plungers have sealing elements that make contact with the inside walls of the tubing. As the plunger travels from the bottom of a well to the surface, the tubing is kept wiped clean, therefore eliminating the buildup or accumulation of paraffin, hydrates, scale, etc.
Lower Capital Cost vs. Installing Beam Lift Equipment
The costs of installing and maintaining a plunger lift are generally lower than the cost to install and maintain a beam pumping unit
Lower Well Maintenance and Fewer Remedial Treatments
Overall well maintenance costs are reduced because periodic remedial treatments such as swabbing or well blow downs are reduced or no longer required with a plunger lift system.
Continuous Production Improves Gas Production Rates and Increases Efficiency
Plunger lift systems can conserve the wells lifting energy and increase gas production. fluid removal allows the well to produce gas continuously and prevent fluid loading that periodically halts gas production or kills the well. Often, the continuous removal of fluids results in daily gas production rates that are higher than the production rates prior to the plunger lift installation.
Reduced Paraffin and Scale Buildup
In wells where paraffin or scale buildup is a problem, the mechanical action of the plunger running up and down the tubing may prevent particulate build up inside the tubing. As a result, the need for chemical or swabbing treatments may be reduced or eliminated. Many different types of plungers are manufactured with scraping performance.
Other Economic Benefits
In calculating the economic benefits of plunger lifts, the average savings from avoided emissions are only one of many factors to consider in the analysis. Additional savings may result from the salvage value of surplus production equipment and the associated reduction in electricity and work over costs. Furthermore, wells that move fluids continuously out of the well bore have the potential to produce more desirable product.